Next Article in Journal
Steroidal Saponins from the Rhizomes of Anemarrhena asphodeloides
Next Article in Special Issue
Optimized Conditions for Passerini-Smiles Reactions and Applications to Benzoxazinone Syntheses
Previous Article in Journal
Immobilization of Glycoside Hydrolase Families GH1, GH13, and GH70: State of the Art and Perspectives
Previous Article in Special Issue
Microwave-Assisted Syntheses of Bioactive Seven-Membered, Macro-Sized Heterocycles and Their Fused Derivatives
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Molecules
Volume 21
Issue 8
10.3390/molecules21081072
molecules-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Synthesis and Antimicrobial Activity of Some New Thiadiazoles, Thioamides, 5-Arylazothiazoles and Pyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidines

by
Abdou O. Abdelhamid
1,*,
Ibrahim E. El Sayed
2,
Mohamed Z. Hussein
3 and
Mangoud M. Mangoud
3
1
Department of Chemistry, Faculty of Science, Cairo University, Giza 12613, Egypt
2
Department of Chemistry, Faculty of Science, El Menoufia University, Shebin El Koom 32511, Egypt
3
Environmental Research Department, National Center for Social and Criminological Research, Ibn Khaldoun Square, Mohandesin, Zamalek, Giza 11561, Egypt
*
Author to whom correspondence should be addressed.
Molecules 2016, 21(8), 1072; https://doi.org/10.3390/molecules21081072
Submission received: 25 June 2016 / Revised: 9 August 2016 / Accepted: 10 August 2016 / Published: 17 August 2016
(This article belongs to the Collection Heterocyclic Compounds)
Browse Figures
Versions Notes

Abstract

:
A novel series of 1,3,4-thiadiazoles, 5-arylazothiazoles and hexahydropyrimido-[4,5-d][1,2,4]triazolo[4,3-a]pyrimidines were synthesized via reaction of hydrazonoyl halides with each of alkyl carbothioates, carbothioamides and 7-thioxo-5,6,7,8-tetrahydropyrimido-[4,5-d]pyrimidine-2,4(1H,3H)-diones in the presence of triethylamine. The structures of the newly synthesized compounds were established based on their spectral data, elemental analyses and alternative synthetic routes whenever possible. Also, the newly synthesized compounds were screened for their antimicrobial activity against various microorganisms.

1. Introduction

Hydrazonoyl halides have been widely used as reagents for the synthesis of heterocyclic compounds, both through condensation reactions, and as precursors of nitrilimines, which can undergo cycloaddition with dipolarophiles [1,2]. 1,3,4-Thiadiazoles are among the most common heterocyclic pharmacophores. They display a broad spectrum of biological activities, including antimicrobial [3] anticancer [4,5], antioxidant [6], antidepressant [7], anticonvulsant [8,9], and antihypertensive activity [10] as well as acetylcholinesterase inhibition for the treatment of Alzheimer disease [11,12]. In addition, thiazoles can found in drugs developed for the treatment of allergies [13], hypertension [14], inflammation [15], schizophrenia [16], bacterial infections [17], HIV [18], sleep disorders [19] and more recently, for the treatment of pain [20], as fibrinogen receptor antagonists with antithrombotic activity [21], and as new inhibitors of bacterial DNA gyrase B [22]. 1,2,4-Triazolopyrimidines have also attracted growing interest due to their important pharmacological activities, such as antitumor, antimalarial, antimicrobial, anti-inflammatory, antifungal properties, and their potency in macrophage activation [23,24,25,26,27].

2. Results and Discussion

Treatment of methyl 2-methylenehydrazinecarbodithioates 3a and [28] 4a with ethyl 2-chloro-2-(2-phenylhydrazono)acetate (5a) in ethanol containing triethylamine gave ethyl 5-({[1H-pyrazol-4-yl]methylene}hydrazono)-1,3,4-thiadiazole-2-caboxylates 9a and 10a, respectively (Scheme 1). The structure 9a was established by elemental analysis, 1H-NMR, IR spectroscopy, mass spectrometry and alternative syntheses. Thus, (5E)-ethyl 5-hydrazono-4,5-dihydro-4-phenyl-1,3,4-thiadiazole-2-carboxylate [29] (11) was reacted with 1a and 1b to give products identical in all aspects (m.p., mixed m.p. and spectra) with 9a and 10a, respectively. In addition, benzyl 2-((1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-methylene)-hydrazine-1-carbodithioate (3b) was reacted with 5a in ethanolic triethylamine to give a product identical in all aspects (m.p., mixed m.p. and spectra) with 9a. In light of the foregoing results, the mechanism outlined in Scheme 1 seems to be the most plausible pathway for the formation of 9 from the reaction of the 5 with 3a or 3b. The reaction involves initial formation of thiohydrazonate 7, which undergoes intermolecular cyclization directly to yield intermediate 8 or via 1,3-dipolar cycloaddition of nitrilimine 6 (generated in situ from 5 with triethylamine) to the C=S of 3 or 4 to yield intermediate 8. Formations of 7 and 8 are similar to the reaction of hydrazonoyl chloride with 1-phenyl-1,4-dihydrotetrazole-5-thione [30] and 5-phenyl-1,3,4-thiadiazole-2(3H)-thione [31]. Intermediate 8 was converted to 9 by elimination of alkyl mercaptan. Analogously, 5b, 5c were reacted separately with 3a, 3b, 4a or 4b in ethanolic triethyamine to afford 2,3-dihydro-1,3,4-thiadiazoles 9b–c and 10a–c, respectively (Scheme 1).
Treatment of 3-(furan-2-yl)-1-(p-tolyl)prop-2-en-1-one (12a), 1-(furan-2-yl)-3-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)prop-2-en-1-one (12b), 3-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-1-(p-tolyl)prop-2-en-1-one (12c), 3-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-1-(p-tolyl)prop-2-en-1-one (12d), 1,3-di(furan-2-yl)prop-2-en-1-one (12e) and 1-(furan-2-yl)-3-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-prop-2-en-1-one (12f) with thiosemicarbazide in boiling ethanol containing potassium hydroxide gave 5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazole-1-carbothioamide (13a), 3’,5-di(furan-2-yl)-1’-phenyl-3,4-dihydro-1’H,2H-[3,4’-bipyrazole]-2-carbothioamide (13b), 3’-(furan-2-yl)-1’-phenyl-5-(p-tolyl)-3,4-dihydro-1’H,2H-[3,4’-bipyrazole]-2-carbothioamide (13c), 1’-phenyl-3’,5-di-p-tolyl-3,4-dihydro-1’H,2H-[3,4’-bipyrazole]-2-carbothioamide (13d), 3,5-di(furan-2-yl)-4,5-dihydro-1H-pyrazole-1-carbothioamide (13e) and 5-(furan-2-yl)-1’-phenyl-3’-(p-tolyl)-3,4-dihydro-1’H,2H-[3,4’-bipyrazole]-2-carbothioamide (13f), respectively (Scheme 2).
Thus, thioamide 13a was reacted with the hydrazonoyl halides 5b and 5c in boiling ethanol containing triethylamine to give 2-(5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-methyl-5-(phenyldiazenyl)thiazole (14a) and 2-(5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-phenyl-5-(phenyldiazenyl)thiazole (15a), respectively (Scheme 3). Thus, benzenediazonium chloride was reacted with 2-(5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-phenyl-thiazole (16), which was prepared via the reaction of 12a with 2-hydrazinyl-4-phenylthiazole [32] (17) or the reaction of compound 13a with ω-bromoacetophenone in pyridine at 0–5 °C to give a product identical in all aspects (mp., mixed mp. and spectra) with 15a (Scheme 3).
Analogously, treatment of the appropriate 13b–f with the hydrazonoyl halides 5b and 5c in boiling ethanol containing triethylamine afforded 2-substituted-4,5-dihydro-1H-pyrazol-1-yl)-4-subsituted-5-(phenyldiazenyl)thiazoles 14b–f and 15b–f, respectively (Scheme 4).
On the other hand, treatment of ethyl 2-chloro-2-(2-phenylhydrazono)acetate (5a) with 5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazole-1-carbothioamide (13a), in boiling ethanol containing triethylamine gave one isolable product according to TLC and proved to be 2-(5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-5-(2-phenylhydrazono)thiazol-4(5H)-one (18a). Also, benzenediazonium was reacted with 2-(5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)thiazol-5(4H)-one (19), which was prepared via the reaction of ethyl chloroacetate with 13a, in ethanolic sodium acetate solution at 0–5 °C to afford a product identical in all aspects (mp, mixed mp and spectra) with 18a (Scheme 5)
Similarly, carbothioamides 13b–d, and 13f were reacted with C-ethoxycarbonyl-N-phenylhydrazonyl chloride in ethanolic triethylamine to give the corresponding thiazolone derivatives 18b–e, respectively (Scheme 6).
In further experiments treatment of 5a with 5,6,7,8-tetrahydro-1,3-dimethyl-5-(1-phenyl-3-p-tolyl-1H-pyrazol-4-yl)-7-thioxopyrimido[4,5-d]pyrimidine-2,4(1H,3H)-dione 20 in boiling chloroform containing triethylamine produced ethyl 2,4-dioxo-1,2,3,4,5,7-hexahydro-pyrimido[5,4-e]-[1,2,4]-triazolo[4,3-a]pyrimidine-9-carboxylate 26a in good yields (Scheme 7).
The 1H-NMR spectrum of 26a showed a triplet at δ 1.18 due to methyl group of ethyl ester, a singlet at δ 2.33 of tolyl methyl group, a singlet at δ 3.33 from the two pyrimidinedione methyl groups, a quartet at δ 4.13 due to the methylene of ethyl ester, a singlet at δ 5.62 that corresponding to the pyrimidine H-4 and a multiplet at δ 6.90–7.83 that account for 14 aromatic protons and H-5 of pyrazole. In the IR spectrum, an absorption peak at 1650 cm−1 corresponding to conjugated carbonyl groups and an absorption near at 1615 cm−1 could account for the presence of the imino group.
The mechanism outlined in scheme 7 seems to be the most plausible pathway for the formation of 26a from the reaction of 5 with 20: (1) 1,3-addition of the thiol tautomer 21 to the nitrilimine 6a would give the thiohydrazonate ester 22 which could undergo nucleophilic cyclization to yield spiro compounds 23. The latter ring could then open and cyclize to yield 26a with loss of hydrogen sulfide; and (2) 1,3-cycloaddition of nitrilimine 6a to C=S of 20 would directly yield 22 (cf., Scheme 7). Attempts to isolate the thiohydrazonate ester 22 or intermediates 23 and 24 did not succeed even under mild conditions as they readily undergo in situ cyclization followed by elimination of hydrogen sulfide to give the final product 26 in Scheme 7.
Analogously, reaction of 20 with each of 5b and 5d afforded 3-acetyl-7,9-dimethyl-1-phenyl-5-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-5,9-dihydropyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine-6,8(1H,7H)-dione (26b) and 7,9-dimethyl-6,8-dioxo-N,1-diphenyl-5-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-1,5,6,7,8,9-hexahydropyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxamide (26c), respectively. Based on the above results, structure 25 was ruled out. This structural assignment was also consistent with literature reports which indicated that reaction of hydrazonoyl halides with 2-thioxopyrimidin-4-one yielded regioselectively the corresponding 1,2,4-triazolo[4,3-a]pyrimidin-5-one derivatives [33]. Additionally, treatment of 5-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-1,3-dimethyl-7-thioxo-5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4(1H,3H)-dione (27) with the hydrazonoyl chlorides 5a and 5d in boiling chloroform in the presence of triethylamine afforded ethyl 5-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-1,3-dimethyl-2,4-dioxo-7-phenyl-1,2,3,4,5,7-hexahydro-pyrimido[5,4-e][1,2,4]triazolo[4,3-a]pyrimidine-9-carboxylate (28a) and 5-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-1,3-dimethyl-2,4-dioxo-N,7-diphenyl-1,2,3,4,5,7-hexahydro-pyrimido[5,4-e][1,2,4]-triazol[4,3-a]pyrimidine-9-carboxamide (28b), respectively (Scheme 8).

3. Antimicrobial Activity

Twenty seven of the newly synthesized target compounds were evaluated for their in vitro antibacterial activity against Staphylococcus aureus and Bacillus subtilis as examples of Gram-positive bacteria and Pseudomonas aeruginosa and Escherichia coli as examples of Gram-negative bacteria. They were also evaluated for their in vitro antifungal activity against a representative panel of fungal strains i.e., Aspergillus fumigatus, and Candida albicans. Ampicillin, Gentamicin and Amphotericin B are used as reference drugs for in vitro antibacterial activity and for in vitro antifungal activity, respectively, at The Regional Center for Mycology and Biotechnology at Al-Azhar University (Nasr City, Cairo, Egypt). The results of testing for antimicrobial effects are summarized in Table 1, Table 2 and Table 3.
Compound 9a had no activity against Aspergillus fumigates, Candida albicans, Streptococcus pneumonia, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli.
  • Candida albicans and Pseudomonas aeruginosa were resistant to compounds 9a, 9b, 9c, 9d, 10a, 10b, 10c, 10d, and 14f.
  • Aspergillus fumigatus was susceptible to compounds 13b, 14b, 15b, and 15c when compared to the Amphotericin B standard.
  • Candida albicans was susceptible to compound 13b when compared to the Amphotericin B standard.
  • Streptococcus pneumoniae was susceptible to compounds 13b, and 14b when compared to the Ampicillin standard.
  • Bacillus subtilis was susceptible to compounds 13b, 14b, and 15b when compared to the Ampicillin standard.
  • Pseudomonas aeruginosa was susceptible to compounds 13b, 15a, and 26d when compared to their standard Gentamicin.
  • Escherichia coli was susceptible to compounds 10a, 13b, 14b, 15f, and 28a when compared to the Gentamicin standard.
The minimum inhibitory concentration (MIC) is the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation. Minimum inhibitory concentrations are important in diagnostic laboratories to confirm resistance of microorganisms to an antimicrobial agent and also to determine the potency of new antimicrobial agents [34]. A MIC is generally regarded as the most basic laboratory measurement of the activity of an antimicrobial agent against an organism [35]. MIC was determined by the broth micro dilution method using 96-well micro-plates [36,37]. Pseudomonas aeruginosa showed an the same as the MIC value of 12.5 mg/mL of the tested compound 13b suggesting high inhibitory activity compared to that of Gentamicin. Also, compound 10a showed an MIC value of 3.9 against Escherichia coli which was the same MIC value of Gentamicin against Escherichia coli (Table 2).
The half maximal inhibitory concentration (IC50) is a measure of the effectiveness of a substance in inhibiting a specific biological or biochemical function. This quantitative measure indicates how much of a particular substance is needed to inhibit a given biological process by half. And here the biological function is the growth of microorganisms Aspergillus fumigatus, Syncephalastrum racemosum, Geotrichum candidum, Candida albicans, Streptococcus pneumoniae, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli (Table 3).

4. Experimental Section

4.1. General Information

All melting points were determined on an Electrothermal apparatus (Bibby Sci. Lim. Stone, Staffordshire, UK) and are uncorrected. IR spectra were recorded (KBr discs) on a FT-IR 8201 PC spectrophotometer (Shimadzu, Tokyo, Japan). 1H-NMR spectra were recorded in CDCl3 and DMSO-d6 solutions on a Gemini 300 MHz spectrometer (Varian, Mercury VX-300 NMR spectrometer, Bruker BioSpin GmbH, Rheinstetten, Germany) and chemical shifts are expressed in δ ppm units using TMS as an internal reference. Mass spectra were recorded on a Shimadzu GC-MS QP1000 EX instrument. (Tokyo, Japan) Elemental analyses were carried out at the Microanalytical Center of Cairo university. Hydrazonoyl halides 5a–d were prepared as previously reported [38,39,40,41]. Antimicrobial screening was performed at the Regional Center for Mycology and Biotechnology, Al-Azhar University, Cairo, Egypt.

4.1.1. General Procedure for the Synthesis of Thiadiazoles 9a–c and 10a–c

Mixtures of alkyl carbodithioate (3a, 3b, 4a or 4b) (5 mmol), hydrazonoyl halides (5a, 5b, or 5c) (5 mmol) and triethylamine (0.75 mL, 5 mmol) in ethanol (20 mL) were stirred at room temperature for 3 h. The resulting solid was collected and recrystallized from acetic acid (dioxane) to give 9a–c and 10a–c, respectively, in good yields.
Ethyl (Z)-5-(((Z)-(1,1’-diphenyl-3'-(p-tolyl)-1H,1'H-[3,4’-bipyrazol]-4-yl)methylene)hydrazono)-4-phenyl-4,5-dihydro-1,3,4-thiadiazole-2-carboxylate (9a). Yellow solid from glacial acetic acid, yield (1.9 g, 75%), mp: 176–177 °C; IR (KBr, cm−1): 3078 (=C–H), 2993–2862 (–C–H), 1708 (–C=O), 1608 (–C=N); 1H-NMR: δ 1.45 (t, 3H, –CH2CH3), 2.43 (s, 3H, 4-CH3C6H4), 4.44 (q, 2H, –OCH2CH3), 7.26–7.97 (m, 18H, Ar–H), 8.95 (s, 1H pyrazole-H-5); MS (m/z): 510 (M + 2, 9), 509 (M + 1, 32), 508 (M+, 72), 259 (52), 246 (41), 91 (57), 77 (100); Anal. Calcd. for C28H24N6O2S (508.59): C, 66.12; H, 4.76; N, 16.52; S, 6.30; found: C, 66.10; H, 4.75; N, 16.53; S, 6.33.
1-((Z)-5-(((Z)-(1,1'-Diphenyl-3'-(p-tolyl)-1H,1'H-[3,4'-bipyrazol]-4-yl)methylene)hydrazono)-4-phenyl-4,5-dihydro-1,3,4-thiadiazol-2-yl)ethan-1-one (9b). Yellow solid from glacial acetic acid, yield (2 g, 84%), mp: 165–166 °C; IR (KBr, cm−1): 3040 (=C–H), 2869 (–C–H), 1674 (–C=O), 1604 (–C=N); 1H-NMR: δ 2.43 (s, 3H, 4-CH3C6H4), 2.68 (s, 3H, –CO–CH3), 7.27–8.02 (m, 14H, Ar–H), 8.50 (s, 1H, –C=H), 8.85 (s, 1H, pyrazole-H-5); MS (m/z): 479 (M + 1, 25), 478 (M+, 32), 310 (35), 307 (34), 150 (33), 138 (38), 126 (30), 122 (39), 91 (37), 77 (26); Anal. Calcd. for C27H22N6OS (478.57): C, 67.75; H, 4.61; N, 17.58; S, 6.70; found: C, 67.76; H, 4.63; N, 17.56; S, 6.71.
((Z)-5-(((Z)-(1,1'-Diphenyl-3'-(p-tolyl)-1H,1'H-[3,4’-bipyrazol]-4-yl)methylene)hydrazono)-4-phenyl-4,5-dihydro-1,3,4-thiadiazol-2-yl)(phenyl)methanone (9c). Orange solid from dioxane, yield (2.27 g, 84%), mp: 264–265 °C; IR (KBr, cm−1): 2863 (C–H), 1700 (–C=O), 1608 (–C=N); 1H-NMR: δ 2.44 (s, 3H, 4-CH3C6H4), 7.27–8.49 (m, 19H, Ar–H), 8.54 (s, 1H, –C=H), 8.96 (s, 1H, pyrazole-H-5); MS (m/z): 542 (M + 2, 57), 541 (M + 1, 59), 540 (M+, 68), 525 (55), 510 (53), 494 (46), 479 (54), 468 (70), 458 (51), 439 (54), 421 (60), 412 (62), 371 (100), 355 (53), 282 (78), 135 (64), 105 (75); Anal. Calcd. for C32H24N6OS (540.64): C, 71.09; H, 4.47; N, 15.54; S, 5.93; found: C, 71.07; H, 4.48; N, 15.54; S, 5.95.
Ethyl (Z)-5-(((Z)-(3'-(furan-2-yl)-1,1'-diphenyl-1H,1'H-[3,4'-bipyrazol]-4-yl)methylene)hydrazono)-4-phenyl-4,5-dihydro-1,3,4-thiadiazole-2-carboxylate (10a). Yellow solid from ethanol, yield (2.2 g, 91%), mp: 171–173 °C; IR (KBr, cm−1): 3108 (=C-H), 2980 (–C–H), 1738 (–C=O), 1603 (–C=N), 1545 (C=C); 1H-NMR: δ 1.44 (t, 3H, –CH2CH3), 4.45 (q, 2H, –OCH2CH3), 6.55 (d, 1H, furyl-H), 6.94 (q, 1H, furyl-H), 7.27–8.03 (m, 11H, Ar–H + 1furyl-H), 8.47 (s, 1H, CH=N), 8.89 (s, 1H, pyrazole-H-5); MS (m/z): 485 (M + 1, 9), 484 (M+, 22), 221 (100), 135 (30), 120 (27), 92 (46), 78 (60); Anal. Calcd. for C25H20N6O3S (484.53): C, 61.97; H, 4.16; N, 17.34; S, 6.62; found: C, 61.99; H, 4.15; N, 17.35; S, 6.60.
1-((Z)-5-(((Z)-(3'-(Furan-2-yl)-1,1'-diphenyl-1H,1'H-[3,4'-bipyrazol]-4-yl)methylene)hydrazono)-4-phenyl-4,5-dihydro-1,3,4-thiadiazol-2-yl)ethan-1-one (10b). Yellow solid from glacial acetic acid, yield (1.3 g, 65%), mp: 200–202 °C; IR (KBr, cm−1): 3021 (=C–H), 2918 (–C–H), 1683 (C=O), 1604 (C=N), 1548 (C=C); 1H-NMR: δ 2.63 (s, 3H, CO–CH3), 6.55 (q, 1H, furyl), 6.89 (d, 1H, furyl), 7.27–7.96 (m, 11H, Ar–H + 1furyl-H), 8.28 (s, 1H, N=CH), 8.91 (s, 1H, pyrazole-H-5); MS (m/z): 454 (M+, 33), 426 (100), 221 (34), 193 (16), 119 (14), 92 (12), 78 (23), 65 (15); Anal. Calcd. for C24H18N6O2S (404.50): C, 63.40; H, 3.98; N, 18.50; S, 7.05; found: C, 63.42; H, 3.99; N, 18.49; S, 7.07.
5-(-((3-(Furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)methylene)hydrazono)-4-phenyl-4,5-dihydro-1,3,4-thiadiazol-2-yl)(phenyl)methanone (10c). Red solid from glacial acetic acid, yield (2.1 g, 83%), mp: 228–230 °C; IR (KBr, cm−1): 3061 (=C–H), 1725 (–C=O), 1601 (–C=N), 1547 (C=C); 1H-NMR: δ 6.56 (q, 1H, furyl-H), 6.85 (d, 1H, furyl-H), 7.27–8.35 (m, 16H, Ar–H + 1furyl-H), 8.35 (s, 1H, CH=N), 8.90 (s, 1H, pyrazole-H-5); MS (m/z): 518 (M + 2, 1), 517 (M + 1, 5), 516 (M+, 31), 502 (12), 487 (97), 167 (10), 135 (25), 131 (10), 235 (17), 221 (49), 193 (24), 129 (17), 119 (11), 106 (100), 78 (45), 65 (30), 51 (45); Anal. Calcd. for C29H20N6O2S (516.57): C, 67.43; H, 3.90; N, 16.27; S, 6.21; found: C, 67.40; H, 3.89; N, 16.27; S, 6.23.

4.1.2. General Procedure for the Synthesis of Chalcones 12a–f

10% NaOH solution (0.2 g, 10 mL, 5 mmol) was added dropwise to a mixture of the appropriate 2-acetylfuran (0.54 g, 5 mmol) or 4-methylacetophenone (0.67 mL, 5 mmol) and the appropriate of 1-phenyl-3-(p-tolyl)-1H-pyrazole-4-carbaldehyde (1a) (1.3 g, 5 mmol), 3-(furan-2-yl)-1-phenyl-1H-pyrazole-4-carbaldehyde (1.2 g, 5 mmol) (1b) or furfuraldehyde (1c) (0.48 g, 5 mmol) in ethanol (30 mL), at 0–5 °C while stirring. The precipitate that formed was filtered, washed with ethanol (10 mL), and recrystallized from ethanol to give 12a–f, respectively.
(E)-3-(Furan-2-yl)-1-(p-tolyl)prop-2-en-1-one (12a). Mp: 64–65 °C (lit. mp: 62–64 °C) [42].
(E)-1-(Furan-2-yl)-3-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)prop-2-en-1-one (12b). Yellow solid from ethanol, yield (1.5 g, 90%), mp: 155–156 °C; IR (KBr, cm−1): 3103 (=C–H), 1652 (C=O); 1H-NMR: δ 6.54 (q, 1H, furyl-H), 6.59 (q, 1H, furyl-H), 6.90 (q, 1H, furyl-H), 7.27–8.33 (m, 11H, ArH’s + 2CH=CH + 3furyl-H + pyrazole-H-5); MS (m/z): 332 (M + 2, 2), 331 (M + 1, 16), 330 (M+, 100), 314 (1), 300 (22), 242 (4), 270 (25), 214 (5), 91 (7); Anal. Calcd. for C20H14N2O3 (330.34): C, 72.72; H, 4.27; N, 8.48; found: C, 72.69; H, 4.28; N, 8.49.
(E)-3-(3-(Furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-1-(p-tolyl)prop-2-en-1-one (12c). Yellow solid, yield (1.63 g, 92%), mp: 146–147 °C; IR (KBr, cm−1): 3122 (=C-H aromatic), 3069 (=C–H), 2919 (–C–H), 1651 (C=O); 1H-NMR: δ 2.44 (s, 3H, 4-CH3C6H4), 6.54 (q, 1H, furyl-H), 6.89 (d, 1H, furyl-H), 7.26–8.19 (m, 12H, Ar–H’s + 2H + 1furyl-H), 8.25 (s, 1H, pyrazole-H-5); MS (m/z): 355 (M + 1, 2), 354 (M+, 7), 308 (20), 281 (25), 234 (43), 209 (27), 208 (42), 207 (28), 181 (13), 180 (43), 179 (20), 178 (15), 168 (16), 167 (36), 166 (100), 154 (13), 153 (44), 152 (32), 140 (38), 139 (10), 127 (13), 126 (10), 115 (16), 114 (10), 113 (13), 63 (10), 29 (30), 27 (13); Anal. Calcd. for C23H18N2O2 (354.40): C, 77.95; H, 5.12; N, 7.90; found: C, 77.97; H, 5.10; N, 7.91.
(E)-3-(1-Phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-1-(p-tolyl)prop-2-en-1-one (12d). mp: 135–136 °C (lit. mp.: 101–103 °C) [43].
(E)-1,3-di(Furan-2-yl)prop-2-en-1-one (12e). Mp: 89–90 °C (lit. mp: 88–90 °C) [39].
1-(Furan-2-yl)-3-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)prop-2-en-1-one (12f) Yellow solid, yield (1.5 g, 86%), mp: 154–155 °C; IR (KBr, cm−1): 3138 (=C–H aromatic), 3105 (=C–H), 2922 (C–H), 1649 (C=O); 1H-NMR: δ 2.44 (s, 3H, 4-CH3C6H4), 6.56 (q, 1H, furyl-H), 7.23–7.97 (m, 13H, ArH’s + 2CH=CH + 2furyl-H), 8.35 (s, 1H, pyrazole-H-5); MS (m/z): 356 (M + 2, 3), 355 (M + 1, 20), 354 (100), 339 (11), 273 (17), 188 (10), 186 (20), 172 (20), 171 (24), 170 (17), 157 (10), 156 (17), 143 (11), 142 (11), 130 (24), 129 (14), 128 (15); Anal. Calcd. for C23H18N2O2 (354.40): C, 77.95; H, 5.12; N, 7.90; found: C, 77.97; H, 5.14; N, 7.88.

4.1.3. Synthesis of Carbothioamide Derivatives 13a–f

Mixtures of chalcones 12a–f (5 mmol) and thiosemicarbazide (0.46 g, 5 mmol) in ethanol (20 mL) were refluxed for 3 h. The resulting solid was collected and recrystallized from acetic acid to give 13a–f, respectively.
5-(Furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazole-1-carbothioamide (13a). Mp: 190–191 °C. (lit. mp: 280–282 °C) [44].
3’,5-di(Furan-2-yl)-1'-phenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazole]-2-carbothioamide (13b). Yellow solid, yield (1.7 g, 85%), mp: 285–287 °C; IR (KBr, cm−1): 3334 (N–H), 3120 (=C–H); 1H-NMR: δ 3.15 (dd, 1H, pyrazoline-H), 3.90 (q, 1H, pyrazoline-H), 6.20 (dd, 1H, pyrazoline-H), 6.65 (m, 2H, furyl-H), 6.67 (q, 1H, furyl-H), 7.05 (d, 1H, furyl-H), 7.44–7.91 (m, 9H, Ar–H + 1furyl-H + 2N–H), 8.95 (s, 1H, pyrazole-H-5); MS (m/z): 404 (M + 1, 2), 403 (M+, 9), 300 (6), 256 (1), 228 (10), 209 (36), 196 (100), 181 (58), 164 (50), 136 (25), 121 (6), 93 (9), 77 (7); Anal. Calcd. for C21H17N5O2S (403.46): C, 62.52; H, 4.25; N, 17.36; S, 7.95; found: C, 62.55; H, 4.26; N, 17.34; S, 7.94.
3’-(Furan-2-yl)-1'-phenyl-5-(p-tolyl)-3,4-dihydro-1'H,2H-[3,4'-bipyrazole]-2-carbothioamide (13c). Yellow solid, yield (1.7 g, 80%), mp: 263–265 °C; IR (KBr, cm−1): 3265 (N–H), 3136 (=C–H aromatic), 3048 (=C–H), 2917 (–C–H); 1H-NMR: δ 2.34 (s, 3H, 4-CH3C6H4), 3.18 (dd, 1H, pyrazoline-H), 3.93 (q, 1H, pyrazoline-H), 6.16 (dd, 1H, pyrazoline-H), 6.65–7.84 (m, 14H, Ar–H + 3furyl-H + 2N–H), 8.08 (s, 1H, pyrazole-H-5); MS (m/z): 427 (M+, 5), 408 (11), 386 (18), 344 (25), 302 (48), 260 (100), 231 (6), 203 (3), 153 (1); Anal. Calcd. for C24H21N5OS (427.52): C, 67.43; H, 4.95; N, 16.38; S, 7.50; found: C, 67.39; H, 4.95; N, 16.38; S, 7.52.
1’-Phenyl-3’,5-di-p-tolyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazole]-2-carbothioamide (13d). White solid from dioxane, yield (1.7 g, 75%), mp: 276–277 °C; IR (KBr, cm−1): 3430; 3115 (N–H), 3046 (=C–H aromatic), 2918 (–C–H); 1H-NMR: δ 2.34 (s, 3H, 4-CH3C6H4), 2.35 (s, 3H, 4-CH3C6H4), 3.18 (dd, 1H, pyrazoline-H), 3.93 (q, 1H, pyrazoline-H), 6.16 (dd, 1H, pyrazoline-H), 6.66–7.82 (m, 15H, Ar–H + 2N–H), 8.07 (s, 1H, pyrazole-H-5); MS (m/z): 452 (M + 1, 6), 253 (17), 250 (13), 225 (16), 221 (10), 206 (19), 193 (20), 174 (14), 151 (9), 142 (29), 116 (10), 110 (16), 108 (17), 107 (16), 91 (100), 84 (43), 82 (26), 79 (20), 82 (26), 77 (12); Anal. Calcd. for C27H25N5S (451.59): C, 71.81; H, 5.58; N, 15.51; S, 7.10; found: C, 71.79; H, 5.57; N, 15.52; S, 7.12.
3,5-di(Furan-2-yl)-4,5-dihydro-1H-pyrazole-1-carbothioamide (13e). Mp: 164–166 °C. (lit. mp: 162–163 °C) [45].
5-(Furan-2-yl)-1'-phenyl-3'-(p-tolyl)-3,4-dihydro-1'H,2H-[3,4'-bipyrazole]-2-carbothioamide (13f). White solid, yield (1.6 g, 76%), mp: 247–248 °C;IR (KBr, cm−1): 3255 (N–H), 3145 (=C–H), 2919 (–C–H); 1H-NMR: δ 2.37 (s, 3H, 4-CH3C6H4), 3.05 (dd, 1H, pyrazoline-H), 3.85 (q, 1H, pyrazoline-H), 6.06 (dd, 1H, pyrazoline-H), 6.65–7.90 (m, 14H, Ar–H + 3furyl-H + 2N–H), 8.01 (s, 1H, pyrazole-H-5); MS (m/z): 427 (M+, 7), 384 (8), 354 (10), 325 (9), 296 (6), 270 (5), 254 (11), 240 (8), 213 (9), 103 (100), 75 (32); Anal. Calcd. for C24H21N5OS (427.52): C, 67.43; H, 4.95; N, 16.38; S, 7.50; found: C, 67.41; H, 4.95; N, 16.37; S, 7.51.

4.1.4. 5-Arylazothiazole Derivatives 14a–f and 15a–f

Method A

Mixtures of the appropriate thioamides 13a–f (5 mmol), the appropriate 5b and 5c (5 mmol) and triethylamine (0.75 mL, 5 mmol) in ethanol (20 mL) were refluxed for 3 h. The resulting solid was collected and recrystallized from acetic acid (or dioxane) to give 14a–f and 15a–f, respectively.

Method B

Benzenediazonium chloride (5 mmol), which was prepared from aniline (0.45 mL, 5 mmol), hydrochloric acid (6 N, 6 mL), and sodium nitrite (0.35 g, 5 mmol), was added dropwise with stirring to a cold solution of 2-(5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazole (16) (1.92 g, 5 mmol) and sodium acetate trihydrate (1.3 g, 10 mmol) in ethanol (50 mL). The reaction mixture was stirred in an ice bath at 0–5 °C for 3 h. The result solid was collected and recrystallized to give a product identical in all aspects (mp, mixed mp. and spectra) with 15a.
(E)-2-(3-(Furan-2-yl)-5-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-methyl-5-(phenyldiazenyl)-thiazole (14a). Red solid, yield (1.5 g, 70%), mp: 179–180 °C; IR (KBr, cm−1): 2920 (–C–H); 1H-NMR: δ 2.37 (s, 3H, 4-CH3C6H4), 2.50 (s, 3H, –CH3), 3.56 (dd, 1H, pyrazoline-H), 3.90 (dd, 1H, pyrazoline-H), 5.90 (dd, 1H, pyrazoline-H), 6.43 (dd, 1H, furyl-H), 6.52 (dd, 1H, furyl-H), 7.31–7.76 (m, 10H, Ar–H + 1furyl-H); MS (m/z): 427 (M+, 1), 326 (12), 236 (16), 232 (14), 206 (39), 204 (11), 194 (31), 147 (51), 146 (14), 134 (23), 133 (41), 129 (11), 121 (32), 118 (12), 117 (100), 115 (10), 107 (24), 91 (17), 73 (24); Anal. Calcd. for C24H21N5OS (427.52): C, 67.43; H, 4.95; N, 16.38; S, 7.50; found: C, 67.41; H, 4.94; N, 16.37; S, 7.51.
(E)-2-(3',5-Di(furan-2-yl)-1'-phenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-4-methyl-5-(phenyldiazen-yl)-thiazole (14b). Red solid, yield (1.5 g, 55%), mp: 275–277 °C; IR (KBr, cm−1): 3146 (=C–H), 2922 (–C–H); 1H-NMR: δ 2.49 (s, 3H, –CH3), 3.13 (dd, 1H, pyrazoline-H), 3.97 (dd, 1H, pyrazoline-H), 6.17 (dd, 1H, pyrazoline-H), 6.65–7.91 (m, 16H, Ar–H + 3-furyl-H), 8.95 (s, 1H, pyrazole-H-5); MS (m/z): 545 (4), 520 (14), 505 (35), 504 (10), 492 (13), 491 (17), 478 (10), 460 (10), 270 (48), 252 (17), 241 (18), 223 (10), 176 (19), 121 (40), 106 (11), 83 (10), 71 (11); Anal. Calcd. for C30H23N7O2S (545.61): C, 66.04; H, 4.25; N, 17.97; S, 5.88; found: C, 66.02; H, 4.24; N, 17.98; S, 5.89.
(E)-2-(3’-(Furan-2-yl)-1’-phenyl-5-(p-tolyl)-3,4-dihydro-1'H,2H-[3,4’-bipyrazol]-2-yl)-4-methyl-5-(phenyl-diazenyl)-thiazole (14c). Red solid, yield (1.7 g, 60%), mp: 250–252 °C; IR (KBr, cm−1): 3139 (=C–H), 2917 (–C–H); 1H-NMR: δ 2.30 (s, 3H, 4-CH3C6H4), 2.50 (s, 3H, –CH3), 3.18 (dd, 1H, pyrazoline-H), 3.97 (dd, 1H, pyrazoline-H), 6.19 (dd, 1H, pyrazoline-H), 6.65–7.88 (m, 17H, Ar–H + 3furyl-H), 8.08 (s, 1H, pyrazole-H-5); MS (m/z): 569 (M+, 4), 484 (16), 454 (14), 358 (42), 317 (60), 289 (34), 230 (34), 130 (16), 103 (26), 77 (14); Anal. Calcd. for C33H27N7OS (569.68): C, 69.57; H, 4.78; N, 17.21; S, 5.63; found: C, 69.55; H, 4.78; N, 17.20; S, 5.64.
(E)-4-Methyl-2-(1'-phenyl-3',5-di-p-tolyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-5-(phenyldiazenyl)-thiazole (14d). Orange solid, yield (2.1 g, 70%), mp: 210–211 °C; IR (KBr, cm−1): 3136 (=C–H aromatic), 3051 (=C–H), 2950 (–C–H); 1H-NMR: δ 2.40 (s, 6H, 4-CH3C6H4), 2.63 (s, 3H, –CH3), 3.65; 3.9 (m, 2H, pyrazoline-H), 5.1 (q, 1H, pyrazoline-H), 6.99–8.95 (m, 19H, Ar–H + pyrazole-H-5); MS (m/z): 593 (M+, 2), 581 (12), 578 (16), 574 (35), 300 (33), 299 (100), 298 (11), 288 (11), 287 (19), 286 (77), 285 (15), 241 (10), 227 (24), 211 (18); Anal. Calcd. for C36H31N7S (593.74): C, 72.82; H, 5.26; N, 16.51; S, 5.40; found: C, 72.85; H, 5.27; N, 16.49; S, 5.39.
(E)-2-(3,5-Di(furan-2-yl)-4,5-dihydro-1H-pyrazol-1-yl)-4-methyl-5-(phenyldiazenyl)-thiazole (14e). Red solid, yield (1.3 g, 66%), mp: 201–203 °C; IR (KBr, cm−1): 3122 (=C–H), 2950 (–C–H); 1H-NMR: δ 2.54 (s, 3H, –CH3), 3.50 (dd, 1H, pyrazoline-H), 3.89 (dd, 1H, pyrazoline-H), 5.90 (dd, 1H, pyrazoline-H), 6.43–6.73 (m, 3H, furyl-H), 7.14 (t, 1H, furyl-H), 7.37–7.97 (m, 7H, Ar–H +2 furyl-H); MS (m/z): 405 (M+2, 3), 404 (M + 1, 21), 403 (M+, 75), 388 (41), 361 (64), 275 (12), 146 (7), 130 (14); Anal. Calcd. for C21H17N5O2S (403.46): C, 62.52; H, 4.25; N, 17.36; S, 7.95; found: C, 62.49; H, 4.25; N, 17.37; S, 7.96.
(E)-2-(5-(Furan-2-yl)-1'-phenyl-3'-(p-tolyl)-3,4-dihydro-1'H,2H-[3,4’-bipyrazol]-2-yl)-4-methyl-5-(phenyldiazenyl)-thiazole (14f). Orange solid, yield (2.1 g, 75%), mp: 216–219 °C; IR (KBr, cm−1): 3120 (=C–H), 2914 (–C–H); 1H-NMR: δ 2.39 (s, 3H, 4-CH3C6H4), 2.47 (s, 3H, –CH3), 4.49 (q, 2H, pyrazoline-H), 5.95 (q, 1H, pyrazoline-H), 6.70 (dd, 1H, furyl-H), 7.05 (d, 1H, furyl-H),7.28–7.61 (m, 15H, Ar–H + 1furyl-H), 8.52 (s, 1H, pyrazole-H-5); MS (m/z): 569 (M+, 7), 553 (10), 398 (12), 370 (15), 248 (51), 235 (100), 91 (27); Anal. Calcd. for C33H27N7OS (569.68): C, 69.57; H, 4.78; N, 17.21; S, 5.63; found: C, 69.58; H, 4.79; N, 17.22; S, 5.62.
(E)-2-(5-(Furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-phenyl-5-(phenyldiazenyl)-thiazole (15a). Orange solid, yield (1.9 g, 76%), mp: 233–234 °C; IR (KBr, cm−1): 3147 (=C–H), 2930 (–C–H); 1H-NMR: δ 2.38 (s, 3H, 4-CH3C6H4), 3.60 (dd, 1H, pyrazoline-H), 4.00 (dd, 1H, pyrazoline-H), 6.00 (dd, 1H, pyrazoline-H), 6.46 (q, 1H, furyl-H), 6.65 (d, 1H, furyl-H), 7.33–8.05 (m, 15H, Ar–H + 1furyl-H); MS (m/z): 489 (M+, 2), 428 (10), 335 (18), 321 (10), 293 (18), 163 (11), 165 (9), 155 (100), 92 (10), 91 (68), 43 (9); Anal. Calcd. for C29H23N5OS (489.59): C, 71.14; H, 4.74; N, 14.30; S, 6.55; found: C, 71.15; H, 4.73; N, 14.31; S, 6.52.
(E)-2-(3',5-di(Furan-2-yl)-1'-phenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-4-phenyl-5-(phenyldiazenyl)-thiazole (15b). Orange solid, yield (1.8 g, 60%), mp: 270–272 °C; IR (KBr, cm−1): 3150 (=C–H); 1H-NMR: δ 3.08 (q, 1H, pyrazoline-H), 3.96 (q, 1H, furyl-H), 6.18 (q, 1H, pyrazoline-H), 6.66–8.10 (m, 22H, Ar–H + pyrazole-H-5 + 6furyl-H); MS (m/z): 607 (M+, 2), 331 (14), 284 (100), 169 (94), 127 (17), 109 (57), 43 (86); Anal. Calcd. for C35H25N7O2S (607.68): C, 69.18; H, 4.15; N, 16.13; S, 5.28; found: C, 69.19; H, 4.16; N, 16.15; S, 5.23.
(E)-2-(3'-(Furan-2-yl)-1'-phenyl-5-(p-tolyl)-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-4-phenyl-5-(phenyldiazenyl)-thiazole (15c). Orange solid, yield (2.3 g, 74%), mp: 240–242 °C; IR (KBr, cm−1): 3139 (=C–H), 2920 (–C–H); 1H-NMR: δ 2.34 (s, 3H, 4-CH3C6H4), 3.18 (dd, 1H, pyrazoline-H), 3.39 (dd, 1H, pyrazoline-H), 6.11 (dd, 1H, pyrazoline-H), 6.64–8.08 (m, 23H, Ar–H + pyrazole-H-5 + 3furyl-H); MS (m/z): 631 (M+, 4), 477 (9), 409 (65), 297 (6), 271 (5), 245 (8), 227 (11), 203 (13), 149 (17), 135 (49), 107 (31), 69 (100); Anal. Calcd. for C38H29N7OS (631.75): C, 72.25; H, 4.63; N, 15.52; S, 5.08; found: C, 72.25; H, 4.62; N, 15.50; S, 5.10.
(E)-4-Phenyl-2-(1'-phenyl-3',5-di-p-tolyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-5-(phenyldiazenyl)-thiazole (15d). Red solid, yield (1.5 g, 45%), mp: 208–209 °C; IR (KBr, cm−1): 3142 (=C–H), 2924 (–C–H); 1H-NMR: δ 2.50 (s, 6H, 4-CH3C6H4), 3.36 (q, 1H, pyrazoline-H), 3.63 (q, 1H, pyrazoline-H), 5.30 (q, 1H, pyrazoline-H), 7.36–9.00 (m, 24H, Ar–H + pyrazole-H-5); MS (m/z): 655 (M+, 1), 498 (10), 339 (10), 281 (17), 243 (51), 242 (62), 210 (12), 171 (32), 156 (25), 73 (35), 71 (76), 41 (26), 39 (14), 27 (19); Anal. Calcd. for C41H33N7S (655.81): C, 75.09; H, 5.07; N, 14.95; S, 4.89; found: C, 75.10; H, 5.05; N, 14.96; S, 4.88.
(E)-2-(3,5-di(Furan-2-yl)-4,5-dihydro-1H-pyrazol-1-yl)-4-phenyl-5-(phenyldiazenyl)-thiazole (15e). Red solid, yield (1.3 g, 57%), mp: 181–183 °C; IR (KBr, cm−1): 3100 (=C–H); 1H-NMR: δ 4.00 (m, 2H, pyrazoline-H), 6.00 (q, 1H, pyrazoline-H), 6.46; 6.64; 6.74 (m, 3H, furyl-H), 7.16 (d, 1H, furyl-H), 7.41–8.27 (m, 12H, Ar–H + 2furyl-H); MS (m/z): 465 (M+, 3), 271 (29), 253 (70), 233 (16), 221 (100), 105 (10); Anal. Calcd. for C26H19N5O2S (465.53): C, 67.08; H, 4.11; N, 15.04; S, 6.89; found: C, 67.10; H, 4.09; N, 15.05; S, 6.86.
(E)-2-(5-(Furan-2-yl)-1'-phenyl-3'-(p-tolyl)-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-4-phenyl-5-(phenyldiazenyl)-thiazole (15f). Orange, yield (1.7 g, 53%), mp: 249–250 °C; IR (KBr, cm−1): 3150 (=C–H), 2922 (–C–H); 1H-NMR: δ 2.37 (s, 3H, 4-CH3C6H4), 3.30 (dd, 1H, pyrazoline-H), 3. 90 (dd, 1H, pyrazoline-H), 6.16 (q, 1H, pyrazoline-H), 6.65 (q, 1H, furyl-H), 7.01 (q, 1H, furyl-H), 7.82–8.10 (m, 21H, Ar–H + pyrazole-H-5 + 1furyl-H); MS (m/z): 633 (M + 2, 1), 632 (M + 1, 8), 631 (M+, 28), 630 (60), 380 (7), 337 (14), 322 (37), 321 (100), 310 (47), 292 (13), 109 (13), 97 (24), 83 (29), 69 (35); Anal. Calcd. for C38H29N7OS (631.75): C, 72.25; H, 4.63; N, 15.52; S, 5.08; found: C, 72.23; H, 4.63; N, 15.51; S, 5.09.
2-(5-(Furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazole (16). A mixture of 5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazole-1-carbothioamide (1.42 g, 5 mmol) and ω-bromo-acetophenone (0.99 g, 5 mmol) in ethanol (30 mL) was heated under reflux for 2 h to give 2-(5-(Furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazole (15) as a white precipitate which was washed with water and recrystallized from glacial acetic acid a white solid, yield (1.9 g, 71%), mp: 221 °C; IR (KBr, cm−1): 3100; 3041 (=C–H), 2943 (–C–H), 1717 (–C=O amide); 1H-NMR: δ 2.45 (s, 3H, 4-CH3C6H4), 3.77 (dd, 1H, pyrazoline-H), 3.93 (dd, 1H, pyrazoline-H), 6.34 (q, 1H, pyrazoline-H), 6.70–7.91 (m, 13H, Ar–H + 3furyl-H + 1thiazole H-5); MS (m/z): 385 (M+, 7%), 381 (3%), 378 (10%), 374 (23%), 369 (51%), 263 (13%), 262 (100%), 260 (12%), 223 (12%), 216 (20%), 215 (12%), 77 (33%), 76 (16%); Anal. Calcd. for C23H19N5O2S (385.48): C, 71.66; H, 4.97; N, 10.90; S, 8.32; found: C, 71.63; H, 4.98; N, 10.92; S, 8.32.

4.1.5. (2-Phenylhydrazono)thiazol-4(5H)-one Derivatives 18a–e

Method A

Equimolar amounts of the appropriate thioamides 13a–d, 13f and ethyl 2-chloro-2-(2-phenylhydrazono)acetate with triethylamine (5 mmol) in ethanol (25 mL) were refluxed for 2 h. The solid so formed was collected and crystallized from glacial acetic acid to afford 2-phenylhydrazono)thiazol-4(5H)-one 18a–e, respectively.

Method B

Benzenediazonium chloride (5 mmol), which prepared from aniline (0.45 mL, 5 mmol), hydrochloric acid (6 N, 6 mL), and sodium nitrite (0.35 g, 5 mmol), was added dropwise with stirring to a cold solution of 19 (5 mmol) and sodium acetate trihydrate (1.3 g, 10 mmol) in ethanol (50 mL). The reaction mixture was stirred in ice bath for 3 h. The resulting solid was collected and crystallized to give a product identical in all aspects (mp, mixed mp, and spectra) with 18a.
(E)-2-(5-(Furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-5-(2-phenylhydrazono)-thiazol-4(5H)-one (18a). Yellow solid, yield (1.4 g, 67%), mp: 247–248 °C; IR (KBr, cm−1): 3432 (N–H), 2970; 2921 (–C–H), 1717 (–C=O amide); 1H-NMR: δ 2.39 (s, 3H, 4-CH3C6H4), 3.63 (dd, 1H, pyrazoline-H), 4.04 (dd, 1H, pyrazoline-H), 5.96 (q, 1H, pyrazoline-H), 6.44 (q, 1H, furyl-H), 6.54 (d, 1H, furyl-H), 6.9–7.78 (m, 10H, Ar–H + 1furyl-H), 10.4 (s, 1H, N–H); MS (m/z): 431 (M + 2, 1), 430 (M + 1, 29), 429 (M+, 100), 413 (15), 346 (15), 345 (40), 316 (10), 264 (23), 263 (11), 248 (10), 228 (58), 227 (25), 226 (16), 214 (44), 212 (12), 200 (12), 198 (11), 196 (16), 186 (14), 172 (11), 170 (13), 158 (14), 157 (10), 156 (13), 146 (17), 144 (18), 130 (16), 115 (10); Anal. Calcd. for C23H19N5O2S (429.49): C, 64.32; H, 4.46; N, 16.31; S, 7.47; found: C, 64.33; H, 4.46; N, 16.32; S, 7.44.
(Z)-2-(3',5-di(Furan-2-yl)-1'-phenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-5-(2-phenylhydrazono)-thiazol-4(5H)-one (18b). Yellow solid, yield (1.7 g, 63%), mp: 284–285 °C; IR (KBr, cm−1): 3407 (N–H), 3044 (=C–H), 2852 (–C–H), 1635 (C=O); 1H-NMR: δ 3.08 (dd, 1H, pyrazoline-H), 3.90 (dd, 1H, pyrazoline-H), 6.19 (dd, 1H, pyrazoline-H), 6.66–7.90 (m, 17H, Ar–H + 1N–H + 6furyl-H), 8.09 (s, 1H, pyrazole-H-5); MS (m/z): 549 (M + 2, 1), 548 (M + 1, 6), 547 (M+, 16), 374 (100), 329 (7), 254 (19), 227 (61), 212 (17), 173 (77), 91 (9), 77 (7); Anal. Calcd. for C29H21N7O3S (547.59): C, 63.61; H, 3.87; N, 17.91; S, 5.86; found: C, 63.61; H, 3.88; N, 17.93; S, 5.80.
(E)-2-(3'-(Furan-2-yl)-1'-phenyl-5-(p-tolyl)-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-5-(2-phenylhydrazono)-thiazol-4(5H)-one (18c). Yellow solid, yield (1.5 g, 54%), mp: 245–247 °C; IR (KBr, cm−1): 3396 (N-H), 3140 (=C–H), 2990 (–C–H), 1715 (–C=O); 1H-NMR: δ 2.34 (s, 3H, 4-CH3C6H4), 3.18 (dd, 1H, pyrazoline-H), 3.90 (dd, 1H, pyrazoline-H), 6.17 (dd, 1H, pyrazoline-H), 6.65–8.08 (m, 19H, Ar–H + 3furyl-H + 1N–H + 1pyrazole-H-5); MS (m/z): 571 (M+, 2), 569 (4), 553 (10), 398 (12), 370 (15), 248 (51), 235 (100), 155 (12), 107 (10), 91 (27), 77 (2), 55 (9); Anal. Calcd. for C32H25N7O2S (571.65): C, 67.23; H, 4.41; N, 17.15; S, 5.61; found: C, 67.25; H, 4.41; N, 17.13; S, 5.60.
(E)-2-(1'-Phenyl-3',5-di-p-tolyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-5-(2-phenylhydrazono)-thiazol-4(5H)-one (18d). Yellow solid, yield (1.6 g, 55%), mp: 278–279 °C; IR (KBr, cm−1): 3431 (N–H), 3140 (=C–H), 2919 (–C–H), 1715 (–C=O); 1H-NMR: δ 2.34 (s, 3H, 4-CH3C6H4), 2.36 (s, 3H, CH3), 3.30 (dd, 1H, pyrazoline-H), 3.85 (dd, 1H, pyrazoline-H), 6.10 (dd, 1H, pyrazoline-H), 7.24–8.08 (m, 20H, 18Ar-H + 1N–H + pyrazole-H-5); MS (m/z): 595 (M+, 1), 578 (11), 554 (6), 397 (10), 340 (7), 279 (100), 263 (4), 236 (29), 193 (28), 91 (1); Anal. Calcd. for C35H29N7OS (595.72): C, 70.57; H, 4.91; N, 16.46; S, 5.38; found: C, 70.58; H, 4.92; N, 16.49; S, 5.32.
(E)-2-(5-(Furan-2-yl)-1'-phenyl-3'-(p-tolyl)-3,4-dihydro-1'H,2H-[3,4'-bipyrazol]-2-yl)-5-(2-phenylhydrazono)-thiazol-4(5H)-one (18e). Yellow solid, yield (2.1 g, 75%), mp: 294–296 °C; IR (KBr, cm−1): 3433 (N-H), 3137 (=C–H), 2921 (–C–H), 1708 (–C=O); 1H-NMR: δ 2.37 (s, 3H, 4-CH3C6H4), 3.40 (dd, 1H, pyrazoline-H), 4.10 (dd, 1H, pyrazoline-H), 5.90 (q, 1H, pyrazoline-H), 6.72 (q, 1H, furyl-H), 6.90–7.99 (m, 16H, Ar–H + 2furyl-H), 8.52 (s, 1H, pyrazole-H-5), 10.33(s, 1H, N-H); MS (m/z): 571 (M+, 2), 553 (10), 398 (12), 370 (15), 248 (51), 235 (100), 155 (12), 107 (10), 91 (27), 71 (4); Anal. Calcd. for C32H25N7O2S (571.65): C, 67.23; H, 4.41; N, 17.15; S, 5.61; found: C, 67.20; H, 4.41; N, 17.13; S, 5.64.
2-(5-(Furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-thiazol-5(4H)-one (19) Equimolar amounts of 5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazole-1-carbothioamide (13a, 1.42 g, 5 mmol) and ethyl chloroacetate (0.61 g, 5 mmol) in ethanol (25 mL) were heated under reflux for 2 h, then allowed to cool at room temperature, the solid so formed was collected and recrystallized from dioxane to give 18 as a pale yellow solid, yield (1.2 g, 72%), mp: 244–245 °C; IR (KBr, cm−1): 3143 (=C–H aromatic), 3039 (=C–H), 2991 (–C–H), 1697 (C=O); 1H-NMR: δ 2.44 (s, 3H, 4-CH3C6H4), 3.61 (dd, 1H, pyrazoline-H), 3.92 (s, 2H, thiazole-H), 3.95 (dd, 1H, pyrazoline-H), 5.85 (q, 1H, pyrazoline-H), 6.42–7.76 (m, 7H, 4Ar-H + 3furyl-H); MS (m/z): 327 (M + 2, 1), 326 (M + 1, 10), 325 (M+, 50), 308 (47), 293 (100), 275 (51), 101 (35), 77 (40), 69 (67); Anal. Calcd. for C17H15N3O2S (325.38): C, 62.75; H, 4.65; N, 12.91; S, 9.85; found: C, 62.74; H, 4.67; N, 12.92; S, 9.81.

4.1.6. General Procedure for the Synthesis of Compounds 20 and 27

Equimolar amounts of the appropriate pyrazole aldehyde 1a or 2b (10 mmol), N,N`-dimethylbarbituric acid (1.56 g, 10 mmol), thiourea (0.76 g, 10 mmol) and conc. hydrochloric acid (5 mL) in ethanol (25 mL) were heated under refluxed for 1 h. The reaction mixture was allowed to cool to room temperature and the precipitate was filtered and crystallized from dioxane to give compounds 20 and 27, respectively.
1,3-Dimethyl-5-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-7-thioxo-5,6,7,8-tetrahydro-pyrimido[4,5-d]pyrimidine-2,4(1H,3H)-dione (20). Yellow solid, yield (4.3 g, 94%), mp: 267–268 °C; IR (KBr, cm−1): 3434 (N–H), 3175 (=C-H aromatic), 3019 (C=H), 2921 (–C–H), 1669 (C=O); 1H-NMR: δ 2.45 (s, 3H, 4-CH3C6H4), 3.40 (s, 3H, N–CH3), 3.44 (s, 3H, N–CH3), 7.27–7.93 (m, 11H, Ar-H + pyrimidine-H-5 + pyrazole-H-5), 8.62 (s, 1H, N–H), 9.88 (s, 1H, N–H); MS (m/z): 460 (M + 2, 2), 459 (M + 1, 12), 458 (M+, 36), 426 (73), 398 (33), 394 (28), 383 (52), 368 (38), 367 (100), 365 (16), 305 (10), 289 (34); Anal. Calcd. for C24H22N6O2S (458.54): C, 62.86; H, 4.84; N, 18.33; S, 6.99; found: C, 62.86; H, 4.85; N, 18.34; S, 6.98.
5-(3-(Furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-1,3-dimethyl-7-thioxo-5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4(1H,3H)-dione (27). Brown solid, yield (3.6 g, 85%), mp: 186–187 °C; IR (KBr, cm−1): 3439 (N-H), 3170 (=C–H), 2954 (–C–H), 1664 (C=O); 1H-NMR: δ 3.44 (s, 6H, 2N–CH3), 6.59–7.90 (m, 10H, ArH + 3furyl-H + pyrimidine-H+ pyrazole-H-5), 9.13 (s, 1H, N–H), 9.85 (s, 1H, N–H); MS (m/z): 434 (M+1, 3), 433 (M+, 5), 310 (100), 296 (51), 238 (49), 168 (28), 166 (34), 150 (17), 139 (59), 138 (42), 125 (74), 99 (11), 83 (14), 43 (22); Anal. Calcd. for C21H18N6O3S (434.47): C, 58.05; H, 4.18; N, 19.34; S, 7.38; found: C, 58.01; H, 4.19; N, 19.36; S, 7.38.

4.1.7. General procedure for the Synthesis of Hexahydropyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine Derivatives 26a–c and 28a,d

Equimolar amounts of 20 (2.29 g, 5 mmol) or 27 (2.17 g, 5 mmol) and the appropriate hydrazonyl halides 5a–d (5 mmol) in ethanol (25 mL) containing 5 drops of triethylamine was heated under reflux for 20 h. The reaction mixture was evaporated under reduced pressure and the resulting solid was washed several times with water and ether. The precipitates formed, were filtered and recrystallized to give:
Ethyl 7,9-dimethyl-6,8-dioxo-1-phenyl-5-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-1,5,6,7,8,9-hexahydropyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (26a). White solid from glacial acetic acid, yield (2.4 g, 77%), mp: 250–251 °C; IR (KBr, cm−1): 3108 (=C–H aromatic), 3038 (=C–H), 2965; 2916 (–C–H), 1696 (C=O); 1H-NMR: δ 1.28 (t, 3H,–CH2CH3), 2.34 (s, 3H, 4-CH3C6H4), 2.82 (s, 3H, N–CH3), 2.86 (s, 3H, N–CH3), 4.30 (q, 2H,-OCH2CH3), 5.59 (s, 1H, pyrimidine-H), 6.88–7.7 (m, 14H, Ar–H), 7.77 (s, 1H, pyrazole-H-5); MS (m/z): 614 (M+, 9), 563 (6), 379 (10), 323 (54), 311 (30), 295 (100), 284 (11), 267 (19), 239 (4), 111 (12), 96 (22), 85 (18), 71 (26); Anal. Calcd. for C34H30N8O4 (614.65): C, 66.44; H, 4.92; N, 18.23; found: C, 66.43; H, 4.91; N, 18.21.
3-Benzoyl-7,9-dimethyl-1-phenyl-5-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-7,9-dihydropyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine-6,8(1H,5H)-dione (26b). White solid from toluene, yield (1.6 g, 50%), mp: 211–213 °C; IR (KBr, cm−1): 3049 (=C–H), 2920 (–C–H), 1695 (–C=O); 1H-NMR: δ 2.43 (s, 3H, 4-CH3C6H4), 2.80 (s, 3H, N–CH3), 2.88 (s, 3H, N–CH3), 5.85 (s, 1H, pyrimidine-H), 6.86–7.68 (m, 19H, Ar-H), 8.32 (s, 1H, pyrazole-H-5); MS (m/z): 646 (M+, 3), 645 (6), 662 (5), 406 (13), 389 (54), 256 (12), 239 (14), 195 (11), 168 (13), 151 (100), 135 (29), 106 (17), 85 (30); Anal. Calcd. for C38H30N8O3 (646.70): C, 70.58; H, 4.68; N, 17.33; found: C, 70.56; H, 4.68; N, 17.34.
7,9-Dimethyl-6,8-dioxo-N,1-diphenyl-5-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-1,5,6,7,8,9-hexahydropyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxamide (26c). White solid from glacial acetic acid, yield (2 g, 60%), mp: 258–259 °C; IR (KBr, cm−1): 3364 (N–H), 3136 (=C–H aromatic), 3054 (=C–H), 2921 (–C–H), 1690 (C=O); 1H-NMR: δ 2.42 (s, 3H, 4-CH3C6H4), 2.80 (s, 3H, N–CH3), 2.87 (s, 3H, N–CH3), 5.76 (s, 1H, pyrimidine-H), 6.86–7.68 (m, 19H, Ar-H), 7.78 (s, 1H, pyrazole-H-5), 8.55 (s, 1H, N–H); MS (m/z): 661 (M + 1, 3), 660 (M+, 7), 603 (9), 441 (11), 401 (1), 315 (29), 204 (100), 189 (46), 161 (12), 147 (56), 121 (3); Anal. Calcd. for C38H31N9O3 (661.71): C, 68.97; H, 4.72; N, 19.05; found: C, 68.93; H, 4.73; N, 19.07.
Ethyl 5-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-7,9-dimethyl-6,8-dioxo-1-phenyl-1,5,6,7,8,9-hexahydropyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (28a). White solid from benzene, yield (2.2 g, 75%), mp: 249–251 °C; IR (KBr, cm−1): 3038 (=C–H), 2969 (–C–H), 1696 (C=O); 1H-NMR: δ 1.28 (t, 3H, –CH2CH3), 2.82 (s, 3H, N–CH3), 2.85 (s, 3H, N–CH3), 4.27 (q, 2H, –OCH2 CH3), 5.58 (s, 1H, pyrimidine-H), 6.87–7.69 (m, 13H, Ar–H + 3furyl-H), 7.75 (s, 1H, pyrazole-H-5); MS (m/z): 590 (M+, 1), 511 (2), 397 (10), 340 (7), 279 (100), 236 (29), 193 (28); Anal. Calcd. for C31H26N8O5 (590.59): C, 63.04; H, 4.44; N, 18.97; found: C, 63.01; H, 4.46; N, 18.91.
5-(3-(Furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-7,9-dimethyl-6,8-dioxo-N,1-diphenyl-1,5,6,7,8,9-hexahydropyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxamide (28b). White solid from toluene, yield (1.7 g, 55%), mp: 145–146 °C; IR (KBr, cm−1): 3398 (N–H), 3130 (=C-H aromatic), 3028 (=C–H), 2949 (–C–H); 1H-NMR: δ 2.84 (s, 3H, N–CH3), 3.35 (s, 3H, N–CH3), 6.03 (s, 1H, pyrimidine-H), 6.53 (q, 1H, furyl-H), 6.91–7.67 (m, 17H, Ar–H + 2furyl-H), 8.73 (s, 1H, pyrazole-H-5), 8.54 (s, 1H, N–H); MS (m/z): 637 (M+, 7), 633 (17), 620 (24), 528 (11), 436 (25), 418 (34), 380 (24), 278 (18), 263 (66), 232 (34), 219 (100), 203 (57), 159 (89); Anal. Calcd. for C35H27N9O4 (637.65): C, 65.93; H, 4.27; N, 19.77; found: C, 65.90; H, 4.28; N, 19.73.

4.2. Antimicrobial Activity Assay

Chemical compounds under investigation were individually tested against a panel of Gram-positive and Gram-negative bacteria pathogens, and fungi. Antimicrobial tests were carried out using the agar well-diffusion method [46]. After the media had cooled and solidified, wells (6 mm in diameter) were made in the solidified agar, after that microbial inoculum was uniformly spread using sterile cotton swab on a sterile Petri dish containing nutrient agar (NA) medium or Sabouraud dextrose agar (SDA) media for bacteria and fungi, respectively. A 100 µL solution was prepared from 1 mL of DMSO by dissolving 1 mg of the compound. The inoculated plates were then incubated for 24 h at 37 °C for bacteria and yeast, 48 h at 28 °C for fungi. Negative controls were prepared using DMSO employed for dissolving the tested compound. Amphotericin B (1 mg/mL), ampicillin (1 mg/mL), and gentamicin (1 mg/mL) were used as standards for bacteria and fungi, respectively. After incubation, antimicrobial activity was evaluated by measuring the zone of inhibition against tested microorganisms. Antimicrobial activity was expressed as inhibition diameter zones in millimeters (mm). The experiment was carried out in triplicate and the average zones of inhibition ± S.D were calculated.

5. Conclusions

New series of novel functionalized 1,3,4-thiadiazoles, 1,3-thiazoles, and pyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidines containing pyrazole moieties were synthesized using hydrazonoyl halides as precursors and evaluated for their in vitro antibacterial, and antifungal activities. From the screening results, it can be seen Aspergillus fumigatus was susceptible to compounds 12b, 13b, 14b, 15b, and 15c when compared to the amphotericin B standard. Candida albicans was susceptible to compounds 12b and 13b when compared to the amphotericin B standard. Streptococcus pneumoniae was susceptible to compounds 12b, 13b, and 14b when compared to an ampicillin standard. Bacillus subtilis was susceptible to compounds 13b, 14b, and 15b when compared to ampicillin standard. Pseudomonas aeruginosa was susceptible to compounds 12b, 13b, 15a, and 26d when compared to Gentamicin standard. Escherichia coli was susceptible to compounds 10a, 12b, 13b, 14b, 15f, and 28a when compared to the gentamicin standard.

Acknowledgments

The authors would like to thank the Chemistry Department, Faculty of Science, Cairo University and National Center for Social and Criminological Research for their financial support to facilitate the publication of this study.

Author Contributions

A.O.A. designed research and analyzed the data. M.N.M. performed experiments. All authors contributed wrote and approved the manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Shawali, A.S.; Abdelhamid, A.O. Synthesis of Spiro-heterocycles via 1,3-Dipolar Cycloadditions of Nitrilimines to Exoheterocyclic Enones. Site-, Regio- and Stereo-Selectivities. Curr. Org. Chem. 2012, 16, 2673–2689. [Google Scholar]
  2. Abdelhamid, A.O.; Gomha, S.M.; Shawali, A.S. Utility of N-aryl 2-aroylhydrazono propanehydrazonoyl chlorides as precursors for synthesis of new functionalized 1,3,4-thiadiazoles with potential antimicrobial activity. J. Adv. Res. 2015, 6, 885–893. [Google Scholar] [CrossRef] [PubMed]
  3. Padmavathi, V.; Reddy, G.S.; Padmaja, A.; Kondaiah, P.; Shazia, A. Synthesis, antimicrobial and cytotoxic activities of 1,3,4-oxadiazoles,1,3,4-thiadiazoles and 1,2,4-triazoles. Eur. J. Med. Chem. 2009, 44, 2106–2112. [Google Scholar] [CrossRef] [PubMed]
  4. Dawood, K.M.; Eldebss, T.M.A.; El-Zahabi, H.S.; Yousef, M.H.; Metz, P. Synthesis of some new pyrazole-based 1,3-thiazoles and 1,3,4-thiadiazoles as anticancer agents. Eur. J. Med. Chem. 2013, 70, 740–749. [Google Scholar] [CrossRef] [PubMed]
  5. Juszczak, M.; Matysiak, J.; Szeliga, M.; Pozarowski, P.; Rzeski, W. 2-Amino-1,3,4-thiadiazole derivative (FABT) inhibits the extracellular signal-regulated kinase pathway and induces cell cycle arrest in human non-small lung carcinoma cells. Bioorg. Med. Chem. Lett. 2012, 22, 5466–5469. [Google Scholar] [CrossRef] [PubMed]
  6. Khan, I.; Ali, S.; Hameed, S.; Rama, N.H.; Hussain, M.T.; Wadood, A.; Uddin, R.; Ul-Haq, Z.; Khan, A.; Ali, S.; et al. Synthesis, antioxidant activities and urease inhibition of some new 1,2,4-triazole and 1,3,4-thiadiazole derivatives. Eur. J. Med. Chem. 2010, 45, 5200–5207. [Google Scholar] [CrossRef] [PubMed]
  7. Jubie, S.; Ramesh, P.N.; Dhanabal, P.; Kalirajana, R.; Murugananthamb, N.; Antonyc, A.S. Synthesis, antidepressant and antimicrobial activities of some novel stearic acid analogues. Eur. J. Med. Chem. 2012, 54, 931–935. [Google Scholar] [CrossRef] [PubMed]
  8. Dawood, K.M.; Abdel-Gawad, H.; Ragab, E.A.; Ellithey, M.; Mohamed, H.A. Synthesis, anticonvulsant, and anti-inflammatory evaluation of some new benzotriazole and benzofuran-based heterocycles. Bioorg. Med. Chem. 2006, 14, 3672–3680. [Google Scholar] [CrossRef] [PubMed]
  9. Harish, K.P.; Mohana, K.N.; Mallesha, L. Synthesis of indazole substituted-1,3,4-thiadiazoles and their anticonvulsant activity. Drug Invent. Today 2013, 5, 92–99. [Google Scholar] [CrossRef]
  10. Hasui, T.; Matsunaga, N.; Ora, T.; Nishigaki, N.; Imura, Y.; Igata, Y.; Matsui, H.; Motoyaji, T.; Tanaka, T.; Habuka, N.; et al. Identification of Benzoxazin-3-one Derivatives as Novel, Potent, and Selective Nonsteroidal Mineralocorticoid Receptor Antagonists. J. Med. Chem. 2011, 54, 8616–8631. [Google Scholar] [CrossRef] [PubMed]
  11. Skrzypek, A.; Matysiak, J.; Karpinska, M.M.; Niewiadomy, A. Enzyme Inhib. Med. Chem. 2013, 28, 816–823. [Google Scholar]
  12. Skrzypek, A.; Matysiak, J.; Niewiadomy, A.; Bajda, M.; Szymanski, P. Synthesis and biological evaluation of 1,3,4-thiadiazole analogues as novel AChE and BuChE inhibitors. Eur. J. Med. Chem. 2013, 62, 311–319. [Google Scholar] [CrossRef] [PubMed]
  13. Patt, W.C.; Hamilton, H.W.; Taylor, M.D.; Ryan, M.J.; Taylor, D.G., Jr.; Connolly, C.J.C.; Doherty, A.M.; Klutchko, S.R.; Sircar, I.; Steinbaugh, B.A.; et al. Structure-activity relationships of a series of 2-amino-4-thiazole containing renin inhibitors. J. Med. Chem. 1992, 35, 2562–2572. [Google Scholar] [CrossRef] [PubMed]
  14. Sharma, R.N.; Xavier, F.P.; Vasu, K.K.; Chaturvedi, S.C.; Pancholi, S.S. Synthesis of 4-benzyl-1,3-thiazole derivatives as potential anti-inflammatory agents: An analogue-based drug design approach. J. Enzym. Inhib. Med. Chem. 2009, 24, 890–897. [Google Scholar] [CrossRef] [PubMed]
  15. Jaen, J.C.; Wise, L.D.; Caprathe, B.W.; Tecle, H.; Bergmeier, S.; Humblet, C.C.; Heffner, T.G.; Meltzner, L.T.; Pugsley, T.A. 4-(1,2,5,6-Tetrahydro-1-alkyl-3-pyridinyl)-2-thiazolamines: A novel class of compounds with central dopamine agonist properties. J. Med. Chem. 1990, 33, 311–317. [Google Scholar] [CrossRef] [PubMed]
  16. Tsuji, K.; Ishikawa, H. Synthesis and anti-pseudomonal activity of new 2-isocephems with a dihydroxypyridone moiety at C-7. Bioorg. Med. Chem. Lett. 1994, 4, 1601–1606. [Google Scholar] [CrossRef]
  17. Bell, F.W.; Cantrell, A.S.; Hogberg, M.; Jaskunas, S.R.; Johansson, N.G.; Jordon, C.L.; Kinnick, M.D.; Lind, P.; Morin, J.M., Jr.; Noreen, R.; et al. Phenethylthiazolethiourea (PETT) compounds, a new class of HIV-1 reverse transcriptase inhibitors. 1. Synthesis and basic structure-activity relationship studies of PETT analogs. J. Med. Chem. 1995, 38, 4929–4936. [Google Scholar] [CrossRef] [PubMed]
  18. Ergenc, N.; Capan, G.; Gunay, N.S.; Ozkirimli, S.; Gungor, M.; Ozbey, S.; Kendi, E. Synthesis and hypnotic activity of new 4-thiazolidinone and 2-thioxo-4,5-imidazolidinedione derivatives. Arch. Pharm. Pharm. Med. Chem. 1999, 332, 343–347. [Google Scholar] [CrossRef]
  19. Carter, J.S.; Kramer, S.; Talley, J.J.; Penning, T.; Collins, P.; Graneto, M.J.; Seibert, K.; Koboldt, C.; Masferrer, J.; Zweifel, B. Synthesis and activity of sulfonamide-substituted 4,5-diaryl thiazoles as selective cyclooxygenase-2 inhibitors. Bioorg. Med. Chem. Lett. 1999, 9, 1171–1174. [Google Scholar] [CrossRef]
  20. Badorc, A.; Bordes, M.F.; de Cointet, P.; Savi, P.; Bernat, A.; Lale, A.; Petitou, M.; Maffrand, J.P.; Herbert, J.M. New orally active non-peptide fibrinogen receptor (GpIIb-IIIa) antagonists: Identification of ethyl 3-[N-[4-[4-amino[(ethoxycarbonyl)imino]methyl]phenyl]-1,3-thiazol-2-yl]-N-[1-(ethoxycarbonyl)methyl]piperid-4-yl]amino]propionate (SR 121787) as a potent and long-acting antithrombotic agent. J. Med. Chem. 1997, 40, 3393–3401. [Google Scholar] [PubMed]
  21. Rudolph, J.; Theis, H.; Hanke, R.; Endermann, R.; Johannsen, L.; Geschke, F.U. seco-Cyclothialidines: New concise synthesis, inhibitory activity toward bacterial and human DNA topoisomerases, and antibacterial properties. J. Med. Chem. 2001, 44, 619–626. [Google Scholar] [CrossRef] [PubMed]
  22. Fares, M.; Abou-Seri, S.M.; Abdel-Aziz, H.A.; Abbas, S.E.S.; Youssef, M.M.; Eladwy, R.A. Synthesis and antitumor activity of pyrido[2,3-d]pyrimidine and pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives that induce apoptosis through G(1) cell-cycle arrest. Eur. J. Med. Chem. 2014, 83, 155–166. [Google Scholar] [CrossRef] [PubMed]
  23. Astakhov, A.V.; Chernyshev, V.M. Molecular structure of 3-amino[1,2,4]-triazolo-[4,3-a]pyrimidin-5-one in various tautomeric forms: Investigation by DFT and QTAIM methods. Chem. Heterocycl. Compd. 2014, 50, 319–326. [Google Scholar] [CrossRef]
  24. Liu, X.H.; Sun, Z.H.; Yang, M.Y.; Tan, C.X.; Weng, J.Q.; Zhang, Y.G.; Ma, Y. Microwave assistant one pot synthesis, crystal structure, antifungal activities and 3D-QSAR of novel 1,2,4-triazolo[4,3-a]pyridines. Chem. Biol. Drug Des. 2014, 84, 342–347. [Google Scholar] [CrossRef] [PubMed]
  25. Farghaly, T.A.; Hassaneen, H.M.E. Synthesis of pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5- ones as potential antimicrobial agents. Arch. Pharm. Res. 2013, 36, 564–572. [Google Scholar] [CrossRef] [PubMed]
  26. Gomha, S.M. A facile one-pot synthesis of 6,7,8,9-tetrahydrobenzo-[4,5]thieno[2,3-d]-1,2,4-triazolo[4,5-a]pyrimidin-5-ones. Monatsh. Chem. 2009, 140, 213–220. [Google Scholar] [CrossRef]
  27. Gomha, S.M.; Badrey, M.G. Ecofriendly regioselective one-pot synthesis of chromeno[4,3-d][1,2,4]triazolo[4,3-a]pyrimidine. Eur. J. Chem. 2013, 4, 180–184. [Google Scholar] [CrossRef]
  28. Abdelhamid, A.O.; Sayed, I.E.; Hussein, M.Z.; Mangoud, M.M. Synthesis and Antimicrobial Activity of Some New 1,3,4-Thiadiazoles and 3-(Furan-2-yl)-5-(3-(furan-2-yl)-4,5-dihydro-1-phenyl-1H-pyrazol-4-yl)-4,5-dihydropyrazole-1-carbothioamide. World J. Pharm. Sci. 2016, 8, 1654–1663. [Google Scholar]
  29. Abdelhamid, A.O.; Zohdi, H.; Rateb, N. Reactions with hydrazonoyl halides part 21. Reinvestigation of the reactions of hydrazonoyl bromides with 1,1-dicyanothioacetanilide. J. Chem. Res. (S) 1999, 184–185. [Google Scholar] [CrossRef]
  30. Butler, R.N. Comprehensive Heterocyclic Chemistry; Katritzky, A.R., Rees, C.W., Scriven, E.F.V., Eds.; Pergamon Press: New York, NY, USA, 1996; Volume 4, pp. 621–678. [Google Scholar]
  31. Huisgen, R.; Grashey, R.; Seidel, M.; Knupfer, H.; Schmidt, R. 1.3-Dipolare additionen, III. Umsetzungen des diphenylnitrilimins mit carbonyl und thiocarbonyl-verbindungen. Justus. Liebig’s Ann. Chem. 1962, 658, 169–180. [Google Scholar] [CrossRef]
  32. Yadav, R.C.; Sharma, P.K.; Singh, J. Synthesis and biological activity of 4”-substituted-2-(4’-formyl-3’-phenylpyrazole)-4-phenylthiazole. J. Chem. Pharm. Res. 2013, 5, 78–84. [Google Scholar]
  33. Mosselhi, M.A.N. A convenient synthesis of novelderivatives of pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-5,6-dione. Monatsh Chem. 2002, 133, 1297–1304. [Google Scholar] [CrossRef]
  34. Smania, J.A.; Monache, F.D.; Smania, E.F.A.; Cuneo, R.S. Antibacterial activity of steroidal compounds isolated from Ganoderma applanatum (Pers.) Pat. (Aphyllophoromycetideae) fruit body. Int. J. Med. Mushr. 1999, 1, 325–330. [Google Scholar] [CrossRef]
  35. Turnidge, J.D.; Ferraro, M.J.; Jorgensen, J.H. Susceptibility tEst Methods: General Considerations. In American Society of Clinical Microbiology Murray, 8th ed.; Murray, P.R., Baron, E.J., Jorgensen, J.H., Pfaller, M.A., Yolken, R.H., Eds.; Manual of Clinical Microbiology: Washington, DC, USA, 2003; p. 1103. [Google Scholar]
  36. Saini, K.R.K.; Choudhary, S.A.; Joshi, Y.C.; Joshi, P. Solvent free synthesis of chalcones and their antibacterial activities. E-J. Chem. 2005, 2, 224–227. [Google Scholar] [CrossRef]
  37. Bhuiyan, M.M.H.; Hossain, M.I.; Mahmud, M.M.; Al-Amin, M. Microwave-assisted efficient synthesis of chalcones as probes for antimicrobial activities. Chem. J. 2011, 1, 21–28. [Google Scholar]
  38. Shawali, A.S.; Osman, A. Synthesis and reactions of phenylcarbamoyl-arylhydrazidic chlorides. Tetrahedron 1971, 27, 2517–2528. [Google Scholar] [CrossRef]
  39. Shawali, A.S.; Abdelhamid, A.O. Reaction of dimethylphenacylsulfonium bromide with N-nitrosoacetarylamides and reactions of the products with nucleophiles. Bull. Soc. Chem. Jpn. 1976, 49, 321–324. [Google Scholar] [CrossRef]
  40. Eweiss, N.F.; Osman, A. Synthesis of heterocycles. Part II. New routes to acetylthiadiazolines and alkylazothiazoles. J. Heterocycl. Chem. 1980, 17, 1713–1717. [Google Scholar] [CrossRef]
  41. Asiri, A.M.; Zayed, M.E.M.; Ng, S.W. Ethyl 2-chloro-2-(2-phenylhydrazin-1-ylidene)acetate. Acta Cryst. 2011, 67, o1962. [Google Scholar] [CrossRef] [PubMed]
  42. Zheng, C.J.; Jiang, S.M.; Chen, Z.H.; Ye, B.J.; Piao, H.R. Synthesis and anti-bacterial activity of some heterocyclic chalcone derivatives bearing thiofuran, furan, and quinoline moieties. Arch. Pharm. Chem. Life Sci. 2011, 344, 689–695. [Google Scholar] [CrossRef] [PubMed]
  43. Sharma, P.K.; Kumar, S.; Kumar, P.; Kaushik, P.; Kaushik, D.; Dhingra, Y.; Aneja, K.R. Synthesis and biological evaluation of some pyrazolylpyrazolines as anti-inflammatory–antimicrobial agents. Eur. J. Med. Chem. 2010, 45, 2650–2655. [Google Scholar] [CrossRef] [PubMed]
  44. Rateb, N.M.; Zohdi, H.F. Atom-efficient, solvent-free, green synthesis of chalcones by grinding. Synth. Commun. 2009, 39, 2789–2794. [Google Scholar] [CrossRef]
  45. Nasr, M.N.; Said, S.A. Novel 3,3a,4,5,6,7-hexahydroindazole and arylthiazolylpyrazoline derivatives as anti-inflammatory agents. Arch. Pharm. Pharm. Med. Chem. 2003, 336, 551–559. [Google Scholar] [CrossRef] [PubMed]
  46. Chimenti, F.; Maccioni, E.; Secci, D.; Bolasco, A.; Chimenti, P.; Granese, A.; Befani, O.; Turini, P.; Alcaro, S.; Ortuso, F.; et al. Synthesis, molecular modeling studies, and selective inhibitory activity against monoamine oxidase of 1-thiocarbamoyl-3,5-diaryl-4,5-dihydro-(1H)-pyrazole derivatives. J. Med. Chem. 2005, 48, 7113–7122. [Google Scholar] [CrossRef] [PubMed]
  • Sample Availability: Samples of the synthesized compounds are available from the authors.
Molecules 21 01072 sch001 550
Scheme 1. Synthesis of 1,3,4-thiadiazole derivatives 9a–c and 10a–c.
Scheme 1. Synthesis of 1,3,4-thiadiazole derivatives 9a–c and 10a–c.
Molecules 21 01072 sch001
Molecules 21 01072 sch002 550
Scheme 2. Synthesis of thioamide derivatives 13a–f.
Scheme 2. Synthesis of thioamide derivatives 13a–f.
Molecules 21 01072 sch002
Molecules 21 01072 sch003 550
Scheme 3. 2-(5-(Furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-substituted-5-(phenyldiazenyl)thiazole 14a and 15a.
Scheme 3. 2-(5-(Furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-substituted-5-(phenyldiazenyl)thiazole 14a and 15a.
Molecules 21 01072 sch003
Molecules 21 01072 sch004 550
Scheme 4. 4,5-Dihydro-1H-pyrazol-1-yl)-4-phenyl-5-(phenyldiazenyl)thiazole derivatives 14b–f and 15b–f.
Scheme 4. 4,5-Dihydro-1H-pyrazol-1-yl)-4-phenyl-5-(phenyldiazenyl)thiazole derivatives 14b–f and 15b–f.
Molecules 21 01072 sch004
Molecules 21 01072 sch005 550
Scheme 5. Synthesis of 2-(5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-5-(2-phenyl-hydrazono)thiazol-4(5H)-one 18a.
Scheme 5. Synthesis of 2-(5-(furan-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-5-(2-phenyl-hydrazono)thiazol-4(5H)-one 18a.
Molecules 21 01072 sch005
Molecules 21 01072 sch006 550
Scheme 6. Synthesis of 3,5-substituted 4,5-dihydro-1H-pyrazol-1-yl)-5-(2-phenylhydrazono)thiazol-4(5H)-one 18b–e.
Scheme 6. Synthesis of 3,5-substituted 4,5-dihydro-1H-pyrazol-1-yl)-5-(2-phenylhydrazono)thiazol-4(5H)-one 18b–e.
Molecules 21 01072 sch006
Molecules 21 01072 sch007 550
Scheme 7. Synthesis of 1,3-dimethyl-7-phenyl-5-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-9-substituted 5,7-dihydropyrimido[5,4-e][1,2,4]triazolo[4,3-a]pyrimidine-2,4(1H,3H)-dione 26a–c.
Scheme 7. Synthesis of 1,3-dimethyl-7-phenyl-5-(1-phenyl-3-(p-tolyl)-1H-pyrazol-4-yl)-9-substituted 5,7-dihydropyrimido[5,4-e][1,2,4]triazolo[4,3-a]pyrimidine-2,4(1H,3H)-dione 26a–c.
Molecules 21 01072 sch007
Molecules 21 01072 sch008 550
Scheme 8. Synthesis of 5-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-1,3-dimethyl-2,4-dioxo-7-phenyl-9-substituted-1,2,3,4,5,7-hexahydropyrimido[5,4-e][1,2,4]triazolo-[4,3-a]pyrimidines 28a and 28b.
Scheme 8. Synthesis of 5-(3-(furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)-1,3-dimethyl-2,4-dioxo-7-phenyl-9-substituted-1,2,3,4,5,7-hexahydropyrimido[5,4-e][1,2,4]triazolo-[4,3-a]pyrimidines 28a and 28b.
Molecules 21 01072 sch008
Table
Table 1. Mean zone of inhibition beyond well diameter (6 mm) produced on a range of clinically pathogenic microorganisms using (5 mg/mL) concentration of tested samples.
Table 1. Mean zone of inhibition beyond well diameter (6 mm) produced on a range of clinically pathogenic microorganisms using (5 mg/mL) concentration of tested samples.
CompoundAspergillus fumigatus (Fungus)Candida albicans (Fungus)Streptococcus pneumoniae (Gram +ve Bact.)Bacillus subtilis (Gram +ve Bact.)Pseudomonas aeruginosa (Gram −ve Bact.)Escherichia coli (Gram −ve Bact.)
9a000000
9b15.7016.219.8016.3
9c15.6019.619.3014.9
10a16.3018.921.3019.9
10b18.8017.318.2017.9
10c18.6020.620015.9
13b23.725.423.832.417.319.9
13c14.616.910.29.8011.2
13f13.611.715.615.309.4
14a15.915.117.313.311.911.6
14b25.317.622.633.713.119.3
14c10.311.38.310.908.8
14e15.612.517.313.310.310.9
14f0012.611.209.6
15a16.918.317.313.415.113.2
15b22.316.519.530.812.317.6
15c20.818.919.414.913.611.8
15e15.412.919.613.99.78.9
15f21.317.218.220.3020.3
18a17.111.113.914.211.710.3
2015.414.810.912.911.311.6
26a14.710.912.214.911.814.7
26c13.915.617.320.612.514.8
26d14.910.421.823.315.319.1
2716.214.915.615.611.710.8
28a16.313.417.520.8018.9
28b18.615.413.312.708.5
Amphotericin B23.725.4----
Ampicillin--23.832.4--
Gentamicin----17.319.9
Table
Table 2. Antimicrobial activity as MICS, (mg/mL) of tested samples against tested microorganisms.
Table 2. Antimicrobial activity as MICS, (mg/mL) of tested samples against tested microorganisms.
CompoundAspergillus fumigatus (Fungus)Candida albicans (Fungus)Streptococcus pneumoniae (Gram +ve Bact.)Bacillus subtilis (Gram +ve Bact.)Pseudomonas aeruginosa (Gram −ve Bact.)Escherichia coli (Gram −ve Bact.)
9d7.8103.91.95015.63
10a31.2503.93.903.9
10b7.81031.257.81015.63
10c3.903.93.9031.25
13b12.562.53.93.912.515.63
14b2512.515.637.955031.25
15f12.562.53.91.952515.63
28a255062.562.5025
Amphotericin B0.490.49----
Ampicillin--0.490.24--
Gentamicin----15.633.9
Table
Table 3. Antimicrobial activity as half maximal inhibitory concentration (IC50) (mg/mL) of tested samples against tested microorganisms.
Table 3. Antimicrobial activity as half maximal inhibitory concentration (IC50) (mg/mL) of tested samples against tested microorganisms.
CompoundAspergillus fumigatus (Fungus)Syncephalastrum racemosum (Fungus)Geotrichum candidum (Fungus)Candida albicans (Fungus)Streptococcus pneumoniae (Gram +ve Bact.)Bacillus subtillis (Gram +ve Bact.)Pseudomonas aeruginosa (Gram −ve Bact.)Escherichia coli (Gram −ve Bact.)
9d43.2136.2818.24017.5215.63027.34
10a64.3134.2831.17031.2518.24031.56
10b42.6333.4219.63076.3437.25028.37
10c35.2427.5824.63025.1222.41034.25
Amphotericin B11.2416.849.3212.68----
Ampicillin----10.585.29--
Gentamicin------17.9616.24

Share and Cite

MDPI and ACS Style

Abdelhamid, A.O.; El Sayed, I.E.; Hussein, M.Z.; Mangoud, M.M. Synthesis and Antimicrobial Activity of Some New Thiadiazoles, Thioamides, 5-Arylazothiazoles and Pyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidines. Molecules 2016, 21, 1072. https://doi.org/10.3390/molecules21081072

AMA Style

Abdelhamid AO, El Sayed IE, Hussein MZ, Mangoud MM. Synthesis and Antimicrobial Activity of Some New Thiadiazoles, Thioamides, 5-Arylazothiazoles and Pyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidines. Molecules. 2016; 21(8):1072. https://doi.org/10.3390/molecules21081072

Chicago/Turabian Style

Abdelhamid, Abdou O., Ibrahim E. El Sayed, Mohamed Z. Hussein, and Mangoud M. Mangoud. 2016. "Synthesis and Antimicrobial Activity of Some New Thiadiazoles, Thioamides, 5-Arylazothiazoles and Pyrimido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidines" Molecules 21, no. 8: 1072. https://doi.org/10.3390/molecules21081072

Article Metrics

Back to TopTop