http://www.mdpi.com/journal/molecules/special_issues/heterocycles/ {snippet name="submission_info"} http://www.mdpi.com/1420-3049/17/2/1548/ Benzo-condensed four-ring heterocycles, such as benzoxetes 1 and benzothietes 3 represent multi-purpose starting compounds for the preparation of various higher heterocyclic ring systems. The thermal or photochemical valence isomerizations between the benzenoid forms 1,3 and the higher reactive o-quinoid structures 2,4 provide the basis for the synthetic applications. On the other hand, this valence isomerization impedes in particular the generation and storage of 1 because the thermal equilibrium 1 2 is completely on the side of 2. Thus, the number of erroneous or questionable benzoxete structures published to date is surprisingly high. On the contrary, the thermal equilibrium 3 4 is on the side of the benzothietes 3, which makes them easily accessible, especially by different flash vacuum pyrolysis techniques. The present article gives a survey of the preparations of 1 and 2, and tries to stimulate their use in synthetic projects. Naphtho-condensed and higher condensed compounds and compounds with an exocyclic C=O or S=O double bond (lactones, thiolactones, sulfoxides and sulfones) are not covered in this article. http://www.mdpi.com/1420-3049/17/2/1548/ Tue, 07 Feb 2012 00:00:00 CET Molecules 2012-02-07 17 2 Review 1548 1570 1420-3049 Benzoxetes and Benzothietes ¾ Heterocyclic Analogues of Benzocyclobutene 2012-02-07 doi: 10.3390/molecules17021548 Herbert Meier http://www.mdpi.com/1420-3049/17/2/1233/ An efficient synthesis of a highly potent and selective IP (PGI2 receptor) agonist that is not structurally analogous to PGI2 is described. This synthesis is accomplished through the following key steps: Nucleophilic ring-opening of 3-(4-chlorophenyl)-oxazolidin-2-one prepared by a one-pot procedure with 4-piperidinol and selective O-alkylation of 1-(2-(4-chlorophenylamino)ethyl)piperidin-4-ol. The obtained compound is a potent and selective IP agonist displaying a long duration of action. http://www.mdpi.com/1420-3049/17/2/1233/ Tue, 31 Jan 2012 00:00:00 CET Molecules 2012-01-31 17 2 Article 1233 1246 1420-3049 Synthesis of Novel IP Agonists via N-Aminoethyl Cyclic Amines Prepared by Decarboxylative Ring-Opening Reactions 2012-01-31 doi: 10.3390/molecules17021233 Yasuhiro Morita Takeshi Ishigaki Kuniaki Kawamura Ryoji Hayashi Masafumi Isogaya Mika Kitsukawa Mitsuko Miyamoto Masashi Uchida Katsuhiko Iseki http://www.mdpi.com/1420-3049/17/1/971/ Condensation of 3-acetyl-8-ethoxycoumarin (3) with thiosemicarbazide gave ethylidenehydrazinecarbothioamide 5, which was transformed into the thiazolidin-4-one derivatives 6,7. Interaction of 3 with DMF/POCl3 gave b-chloroacroline derivative 8. Treatment of 3 with malononitrile gave benzo[c]chromone and 2-aminobenzonitrile derivatives 9 and 10, respectively with respect to the reaction conditions. Condensation of 3-(2-bromoacetyl)-8-ethoxycoumarin (4) with o-phenylenediamine gave 3-(quioxaline-2-yl)-8-ethoxycoumarin hydrobromide (11), while 4 reacted with 2-aminopyridine to give chromenopyridopyrimidine derivative 12. Condensation of 4 with potassium thio-cyanate/methanol gave an unexpected derivative, 2H-chromeno-3-carboxy(methyl-carbonimidic)thioanhydride 16, which upon treatment with (NH2)2·H2O gave 3-ethoxy-2-hydroxybenzaldehyde azine 19. Interaction of 4 with thiourea derivatives gave thiazole derivatives 20a–c. The structures of the newly synthesized compounds were confirmed by their spectra data. The newly synthesized compounds were also screened for their antimicrobial activity. http://www.mdpi.com/1420-3049/17/1/971/ Wed, 18 Jan 2012 00:00:00 CET Molecules 2012-01-18 17 1 Article 971 988 1420-3049 Synthesis, Reactions and Antimicrobial Activities of 8-Ethoxycoumarin Derivatives 2012-01-18 doi: 10.3390/molecules17010971 Hany M. Mohamed Ashraf H. F. Abd El-Wahab Kamal A. Ahmed Ahmed M. El-Agrody Ahmed H. Bedair Fathy A. Eid Mostafa M. Khafagy http://www.mdpi.com/1420-3049/17/1/897/ 3-Aroyl and 3-heteroaroyl substituted 3-oxoalkanenitriles were synthesized by the reactions of activated aromatic and hetero-aromatic substances with cyanoacetic acid in the presence of acetic anhydride. As part of studies focusing on the preparation of cyanoacetyl-1-N-methylbenzimidazole, we observed that reaction of N-methyl-benzimidazole with the cyanoanhydride formed by condensation of cyanoacetic acid with acetic anhydride, leads to the formation of 2-(1,3-diacetyl-2,3-dihydro-1H-benzo[d]-imidazol-2-yl)acetonitrile (5), whose structure was confirmed by X-ray crystallographic analysis. 3-Oxoalkanenitriles 3a,b were observed to undergo condensation reactions with dimethylformamide dimethyl acetal (DMFDMA) to afford the corresponding enamino-nitriles, which react with malononitrile to give 2-dialkylaminopyridines through a pathway involving a new, unexpected rearrangement process. Reactions of 3-oxoalkanenitriles with ethyl acetoacetate were found to afford 2-oxopyran-3-carbonitriles, also occurring via this unexpected rearrangement process. Mechanisms to account for both rearrangement reactions are suggested. In addition, reactions of 3-oxoalkanenitriles with acetylacetone in acetic acid in the presence of ammonium acetate result in the formation of pyridine-3-carbonitriles. Finally, upon heating in the presence of zeolite 3-oxoalkanenitriles 3b,c self-trimerized to produce the corresponding aniline derivatives 23b,c. http://www.mdpi.com/1420-3049/17/1/897/ Wed, 18 Jan 2012 00:00:00 CET Molecules 2012-01-18 17 1 Article 897 909 1420-3049 Studies on 3-Oxoalkanenitriles: Novel Rearrangement Reactions Observed in Studies of the Chemistry of 3-Heteroaroyl-3-Oxoalkanenitriles as Novel Routes to 2-Dialkylaminopyridines 2012-01-18 doi: 10.3390/molecules17010897 Hamad M. Al-Matar Khaled D. Khalil Mona F. Al-Kanderi Mohamed H. Elnagdi http://www.mdpi.com/1420-3049/17/1/463/ Quantum mechanics density functional calculations provided gas-phase electron distributions and proton affinities for several mono- and diaza[5]helicenes; computational results, together with experimental data concerning crystal structures and propensity to methylation of the nitrogen atom(s), provide a basis for designing azahelicene complexes with transition metal ions. http://www.mdpi.com/1420-3049/17/1/463/ Thu, 05 Jan 2012 00:00:00 CET Molecules 2012-01-05 17 1 Article 463 479 1420-3049 Quantum Mechanics Calculations, Basicity and Crystal Structure: The Route to Transition Metal Complexes of Azahelicenes 2012-01-05 doi: 10.3390/molecules17010463 Tullio Caronna Franca Castiglione Antonino Famulari Francesca Fontana Luciana Malpezzi Andrea Mele Daniele Mendola Isabella Natali Sora http://www.mdpi.com/1420-3049/17/1/227/ A new series of 6-substituted-4-methyl-3-(4-arylpiperazin-1-yl)cinnolines 8–10 were synthesized as potential antifungal agents via intramolecular cyclization of the respective 1-(2-arylhydrazono)-1-(4-arylpiperazin-1-yl)propan-2-ones 5–7, mediated by polyphosphoric acid (PPA). The amidrazones themselves were synthesized via direct interaction of the appropriate hydrazonoyl chlorides 4a–d with the corresponding N-substituted piperazine in the presence of triethylamine. The structures of the new prepared compounds were confirmed by elemental analyses, 1H-NMR, 13C-NMR, and ESI-HRMS spectral data. The antitumor, antibacterial, and antifungal activity of the newly synthesized compounds was evaluated. http://www.mdpi.com/1420-3049/17/1/227/ Wed, 28 Dec 2011 00:00:00 CET Molecules 2011-12-28 17 1 Article 227 239 1420-3049 Synthesis and Biological Activity of Some 3-(4-(Substituted)-piperazin-1-yl)cinnolines 2011-12-28 doi: 10.3390/molecules17010227 Eman D. Awad Mustafa M. El-Abadelah Suzan Matar Malek A. Zihlif Randa G. Naffa Ehab Q. Al-Momani Mohammad S. Mubarak http://www.mdpi.com/1420-3049/16/12/10387/ The formation of (E)-3-{2-(2,5-diphenylpyrazolo[1,5-c]pyrimidin-7-yl)hydrazono}indolin-2-ones 3 has been achieved by condensation of equimolar amounts of 7-hydrazino-2,5-diphenylpyrazolo[1,5-c]pyrimidine (1) and isatin (or isatin derivatives) 2 at room temperature. The (E)-products could be isomerized into corresponding the (Z)-3 isomers. Reactions of the latter fused heterocyclic hydrazones towards different electro-philic reagents yielded the corresponding 3-substituted derivatives 4–7. Dehydrative cyclisation of the hydrazones 3 using phosphorus oxychloride afforded the 2,5-diphenyl- indolo[2,3-e]pyrazolo[1',5':3",4"]pyrimido[2",1"-c][1,2,4] triazines 13. The polyfused heterocyclic ring system 13 underwent electrophilic substitution reactions at position 4 rather than at position 3. The 3-bromo isomer of 17 was prepared by a sequence of reactions starting from 2,5-diphenylpyrazolo[1,5-c]pyrimidine-7(6H)-thione (11). The orientation of the electrophilic attack was supported by spectroscopic and chemical evidence. Some of the synthesized compounds were found to possess slight to moderate activity against the microorganisms Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. http://www.mdpi.com/1420-3049/16/12/10387/ Thu, 15 Dec 2011 00:00:00 CET Molecules 2011-12-15 16 12 Article 10387 10408 1420-3049 Synthesis and Antibacterial Activities of Novel 2,5-Diphenylindolo[2,3-e] Pyrazolo[1',5':3",4"]pyrimido[2",1"-c] [1,2,4]triazines 2011-12-15 doi: 10.3390/molecules161210387 Kamal F.M. Atta Omaima O.M. Farahat Somaya M. Ghobashy Mohamed G. Marei http://www.mdpi.com/1420-3049/16/11/9553/ A copper(I)-mediated one-pot synthesis of 2,3-dihydro-1H-indazole heterocycles has been developed. This synthetic route provides the desired indazoles in moderate to good yields (55%–72%) which are substantially better than those achievable with an alternative two-step reaction sequence. The reaction is tolerant of functionality on the aromatic ring. http://www.mdpi.com/1420-3049/16/11/9553/ Wed, 16 Nov 2011 00:00:00 CET Molecules 2011-11-16 16 11 Article 9553 9561 1420-3049 One-Pot Synthesis of Novel 2,3-Dihydro-1H-indazoles 2011-11-16 doi: 10.3390/molecules16119553 Gary W. Breton Antonio J. Lepore http://www.mdpi.com/1420-3049/16/11/8992/ The reactions of 2-, 3- and 4-aminopyridines with 4,5-dichloro-1,2,3-dithiazol-ium chloride (Appel salt) 4 to give N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)pyridin-X-amines 1a (X = 2), 1g (X = 3) and 1k (X = 4) were optimized with respect to base, temperature and reaction time. Based on these conditions a total of thirteen [(dithiazol-ylidene)amino]azines 1a-m were prepared and fully characterized. http://www.mdpi.com/1420-3049/16/11/8992/ Tue, 25 Oct 2011 00:00:00 CEST Molecules 2011-10-25 16 11 Article 8992 9002 1420-3049 Synthesis of [(4-Chloro-5H-1,2,3-dithiazol-5-ylidene)amino]azines 2011-10-25 doi: 10.3390/molecules16118992 Panayiotis A. Koutentis Maria Koyioni Sophia S. Michaelidou http://www.mdpi.com/1420-3049/16/10/8788/ A series of new 8-arylhydrazono-2-(benzylsulfanyl)-7H-purin-6-ones 6 were synthesized, their electronic absorption spectra in different organic solvents of varying polarities were investigated and their acid dissociation constants in both the ground and excited states were determined spectrophotometrically. The tautomeric structures of such products were elucidated by spectral analyses and correlation of their acid dissociation constants with the Hammett equation. The results indicated that the studied compounds 6 exist predominantly in the hydrazone tautomeric form 6A in both the ground and excited states. http://www.mdpi.com/1420-3049/16/10/8788/ Wed, 19 Oct 2011 00:00:00 CEST Molecules 2011-10-19 16 10 Article 8788 8802 1420-3049 Synthesis, Acidity Constants and Tautomeric Structure of the Diazonium Coupling Products of 2-(Benzylsulfanyl)-7H-purin-6-one in Its Ground and Excited States 2011-10-19 doi: 10.3390/molecules16108788 Elham S. Darwish Mosselhi A. Mosselhi Farag M. Altalbawy Hosam A. Saad http://www.mdpi.com/1420-3049/16/10/8745/ An efficient synthesis of functionalized spiropyrrolizidine oxindoles via a three-component tandem cycloaddition has been achieved. This strategy can provide direct and rapid access to spiropyrrolizidine oxindoles in high yields (up to 99%) with excellent diastereoselectivities (up to 99:1 dr). The features of this procedure are the following: mild reaction conditions, high yields, high diastereoselectivities, one-pot procedure and operational simplicity. http://www.mdpi.com/1420-3049/16/10/8745/ Wed, 19 Oct 2011 00:00:00 CEST Molecules 2011-10-19 16 10 Article 8745 8757 1420-3049 Facile Synthesis of Functionalized Spiropyrrolizidine Oxindoles via a Three-Component Tandem Cycloaddition Reaction 2011-10-19 doi: 10.3390/molecules16108745 Yong-Mei Xie Yu-Qin Yao Hong-Bao Sun Ting-Ting Yan Jie Liu Tai-Ran Kang http://www.mdpi.com/1420-3049/16/9/7736/ A series of 3,5-disubstituted pyrazole-1-carboxamides were obtained by treatment of chalcones with semicarbazide hydrochloride in dioxane containing sodium acetate/acetic acid as a buffer solution. N-acetyl derivatives of pyrazole-1-carboxamides were isolated in good yields either by treatment of the carboxamide derivatives with acetic anhydride or refluxing chalcones with semicarbazide in ethanol containing few drops of acetic acid to give the corresponding hydrazones. Subsequent treatment of hydrazones with acetic anhydride gave the desired N-acetyl pyrazole-1-carboxamides derivatives. When chalcones were refluxed with dioxane containing few drops of acetic acid, 4,5-dihydropyrazole-1-carboxamides were isolated, which were subsequently oxidized using 5% sodium hypochlorite in dioxane to afford pyrazole-1-carboxamides. The structures of isolated compounds were confirmed by elemental analyses and spectral methods. The isolated compounds were tested for their antimicrobial activities. http://www.mdpi.com/1420-3049/16/9/7736/ Fri, 09 Sep 2011 00:00:00 CEST Molecules 2011-09-09 16 9 Article 7736 7745 1420-3049 Synthesis and in Vitro Antimicrobial Activity of Some Pyrazolyl-1-carboxamide Derivatives 2011-09-09 doi: 10.3390/molecules16097736 Essam Mohamed Sharshira Nagwa Mohamed Mahrous Hamada http://www.mdpi.com/1420-3049/16/8/7081/ 5-Aryl-7-hydrazino-2-phenylpyrazolo[1,5-c]pyrimidines 1 were used as precursors for the preparation of a new series of 5-aryl-8-phenylpyrazolo[1,5-c]-1,2,4- triazolo[4,3-a]pyrimidines 2. The reactions of 2 with certain electrophilic reagents gave the respective 6-substituted derivatives 3-5 rather than the 7-isomeric products. Formylation of the key compounds 1 with ethyl formate yielded the formyl derivatives 6. Furthermore, boiling of compounds 1 with acetic acid afforded 7-acetylhydrazino-5-aryl-2-phenylpyrazolo[1,5-c]pyrimidines 7. Bromination of 7 yielded the dibromo- derivatives 8, while their iodination and nitration gave the monosubstituted derivatives 9 and 10, respectively. Also, treatment of 1 with boiling acetic anhydride yielded the triacetyl derivatives 11. The structure of synthesized products was confirmed by elemental analyses, IR, 1H NMR and MS spectra. http://www.mdpi.com/1420-3049/16/8/7081/ Thu, 18 Aug 2011 00:00:00 CEST Molecules 2011-08-18 16 8 Article 7081 7096 1420-3049 Synthesis and Electrophilic Substitutions of Novel Pyrazolo[1,5-c]-1,2,4-triazolo[4,3-a]pyrimidines 2011-08-18 doi: 10.3390/molecules16087081 Kamal F.M. Atta http://www.mdpi.com/1420-3049/16/8/7019/ A series of different 1-monosubstituted and 1,1-disubstituted 1,2,3,4-tetrahydro-isoquinolines was synthesized in high yields from different ketoamides. We have developed a convenient method for the synthesis of disubstituted derivatives by interaction of ketoamides with organomagnesium compounds, followed by cyclization in the presence of catalytic amounts of p-toluenesulfonic acid (PTSA). A number of substituents at the C-1 in the isoquinoline skeleton were introduced varying either carboxylic acid or organomagnesium compound. Some of the obtained 1,1-dialkyl-1,2,3,4-tetrahydro-isoquinolines possess contractile activity against guinea pig’s gastric smooth muscle preparations. http://www.mdpi.com/1420-3049/16/8/7019/ Tue, 16 Aug 2011 00:00:00 CEST Molecules 2011-08-16 16 8 Article 7019 7042 1420-3049 Synthesis and Contractile Activity of Substituted 1,2,3,4-Tetrahydroisoquinolines 2011-08-16 doi: 10.3390/molecules16087019 Iliyan Ivanov Stoyanka Nikolova Dimo Aladjov Iliyana Stefanova Plamen Zagorchev http://www.mdpi.com/1420-3049/16/8/6549/ A novel series of 7,7-diphenyl-1,2-dihydroimidazo[2,1-c][1,2,4]triazin-6(7H)-one 6a–h, were easily prepared via reactions of novel 2-hydrazinyl-4,4-diphenyl-1H-imidazol-5(4H)-one (2) with hydrazonoyl halides 3a–h. In addition, we also examined the reaction of compound 2 with commercially available active methylene compounds to afford new pyrazoles containing an imidazolone moiety, expected to be biologically active. The structures of the synthesized compounds were assigned on the basis of elemental analysis, IR, 1H-NMR and mass spectral data. The antifungal and antibacterial activities of the newly synthesized compounds were evaluated. http://www.mdpi.com/1420-3049/16/8/6549/ Thu, 04 Aug 2011 00:00:00 CEST Molecules 2011-08-04 16 8 Article 6549 6560 1420-3049 Synthesis and Antimicrobial Activity of Some New Pyrazoles, Fused Pyrazolo[3,4-d]-pyrimidine and 1,2-Dihydroimidazo-[2,1-c][1,2,4]triazin-6-one Derivatives 2011-08-04 doi: 10.3390/molecules16086549 Sobhi Mohamed Gomha Huwaida M.E. Hassaneen http://www.mdpi.com/1420-3049/16/8/6502/ A series of new bis(heterocycles) featuring thieno[2,3-b]thiophene rings was synthesized in a combinatorial manner. Intramolecular cyclization of enaminone derivatives with appropriate N-nucleophiles afforded the target compounds. All compounds were characterized by 1H-, 13C-NMR, GCMS, IR, and UV-Vis spectrometry. These compounds represent a new class of sulfur- and nitrogen-containing heterocycles that should also be of interest as new materials. http://www.mdpi.com/1420-3049/16/8/6502/ Wed, 03 Aug 2011 00:00:00 CEST Molecules 2011-08-03 16 8 Article 6502 6511 1420-3049 1,1’-(3-Methyl-4-phenylthieno[2,3-b]thiophene-2,5-diyl)diethanone as a Building Block in Heterocyclic Synthesis. Novel Synthesis of Some Pyrazole and Pyrimidine Derivatives 2011-08-03 doi: 10.3390/molecules16086502 Yahia Nasser Mabkhot Abdullah Mohammed Al-Majid Assem Barakat Saeed Alshahrani Yamin Siddiqui http://www.mdpi.com/1420-3049/16/8/6470/ A catalytic system consisting of the ruthenium(II) complex [Ru(η3-2-C3H4Me)(CO)(dppf)][SbF6] (dppf = 1,1’-bis(diphenylphosphino)ferrocene) and trifluoroacetic acid has been used to promote the coupling of secondary propargylic alcohols with 6-chloro-4-hydroxychromen-2-one. The reactions afforded unusual 2-methylene-2,3-dihydrofuro[3,2-c]chromen-2-ones in good yields. http://www.mdpi.com/1420-3049/16/8/6470/ Tue, 02 Aug 2011 00:00:00 CEST Molecules 2011-08-02 16 8 Article 6470 6480 1420-3049 Expeditious Entry to Novel 2-Methylene-2,3-dihydrofuro[3,2-c] chromen-2-ones from 6-Chloro-4-hydroxychromen-2-one and Propargylic Alcohols 2011-08-02 doi: 10.3390/molecules16086470 Noel Nebra Alba E. Díaz-Álvarez Josefina Díez Victorio Cadierno http://www.mdpi.com/1420-3049/16/7/6129/ Knoevenagel condensation of 2-(benzothiazol-2-ylthio) acetonitrile (2) with either furan-2-carbaldehyde or thiophene-2-carbaldehydes leads to E-isomers 4a–b exclusively, while the condensation of the compound 2 with benzaldehyde or para-substituted benzaldehydes with an electron-donating group afforded E/Z mixtures 4c–e with preferentially formation of the E-isomer. Condensation of furan-2-carbaldehyde (3a) with either 1-(benzothiazol-2'-ylthio) propan-2-one (5) or 2-(2'-oxo propylthio)-3-phenyl-quinazolin-4(3H)-one (9) leads exclusively to the Z-isomers of 6 and 10, respectively. The structures of the newly synthesized compounds were elucidated by elemental analyses, 1H-NMR and 13C-NMR spectra, COSY, HSQC, HMBC, NOE, MS and X-ray crystallographic investigations. http://www.mdpi.com/1420-3049/16/7/6129/ Wed, 20 Jul 2011 00:00:00 CEST Molecules 2011-07-20 16 7 Article 6129 6147 1420-3049 Synthesis and E/Z Configuration Determination of Novel Derivatives of 3-Aryl-2-(benzothiazol-2'-ylthio) Acrylonitrile, 3-(Benzothiazol-2'-ylthio)-4-(furan-2''-yl)-3-buten-2-one and 2-(1-(Furan-2''-yl)-3'-oxobut-1''-en-2-ylthio)-3-phenylquinazolin-4(3H)-one 2011-07-20 doi: 10.3390/molecules16076129 Fatima Al-Omran Rafat M. Mohareb Adel Abou El-Khair http://www.mdpi.com/1420-3049/13/4/938/ The conversion from kobophenol A into carasinol B, two main chemicalconstituents of Caragana sinica, was confirmed by in vitro acid-catalyzed epimerization.The result provides important information about the biotransformation of kobophenol A inplants and its metabolism in rats. http://www.mdpi.com/1420-3049/13/4/938/ Sat, 19 Apr 2008 00:00:00 CEST Molecules 2008-04-19 13 4 Communication 938 942 1420-3049 Acid-catalyzed Epimerization of Kobophenol A to Carasinol B 2008-04-19 doi: 10.3390/molecules13040938 Kejun Cheng Gaolin Liang Changqi Hu http://www.mdpi.com/1420-3049/12/8/1940/ This paper reports the preparation, characterization and the crystal X-ray structures of metal-containing ionic liquid complexes based on chiral pyridinium cations and tetrachloropalladate (II) [PdCl4]2-. http://www.mdpi.com/1420-3049/12/8/1940/ Mon, 20 Aug 2007 00:00:00 CEST Molecules 2007-08-20 12 8 Article 1940 1949 1420-3049 Palladate Salts from Chiral Pyridinium Ionic Liquids: Synthesis and Crystal Structures 2007-08-20 doi: 10.3390/12081940 Emmanuel Tourneux Heinz Gornitzka Jean-Daniel Marty Nancy Lauth-de Viguerie http://www.mdpi.com/1420-3049/12/8/1623/ 2,3-Dicyano-5,7-bismethylthieno[3,4-b]pyrazine (5), has been obtained as a minor product from reactions of S-nucleophiles with 5,6-di(1-bromoethyl)pyrazine-2,3- dicarbonitrile (3), or from a condensation of 4-hydroxy-2,5-dimethyl-2,3-dihydrothiophen- 3-one (4) with diaminomaleonitrile. The molecular structure of compound 5 has been confirmed by X-ray diffraction. A partial separation of charge causes a donor-acceptor type arrangement of the planar molecules in uniform parallel stacks with an interplanar spacing of 3.334(2) Å at 100 K. http://www.mdpi.com/1420-3049/12/8/1623/ Mon, 30 Jul 2007 00:00:00 CEST Molecules 2007-07-30 12 8 Article 1623 1631 1420-3049 o-Quinonoid Heterocycles: Synthesis and Crystal Structure of 2,3-Dicyano-5,7-bismethylthieno[3,4-b]pyrazine 2007-07-30 doi: 10.3390/12081623 Eva H. Mørkved Jon A. Beukes Frode Mo http://www.mdpi.com/1420-3049/12/7/1482/ A novel approach to the synthesis of pyrazole derivatives from tosylhydrazones of α,β-unsaturated carbonyl compounds possessing a β-hydrogen is proposed, exploiting microwave (MW) activation coupled with solvent free reaction conditions. The cycloaddition was studied on three ketones (trans-4-phenyl-3-buten-2-one, β-ionone and trans-chalcone). The corresponding 3,5-disubstitued-1H-pyrazoles were obtained in high yields and after short reaction times. In order to simplify and point out the green chemistry features of the method, a further improvement was achieved under the same catalytic conditions with a “one pot” synthesis of these heterocyclic compounds, starting directly from their carbonyl precursors via tosylhydrazones generated in situ. For an exhaustive study, the dielectric properties of the solid reaction mixtures were also measured, in order to obtain input data for the numerical simulation of their heating behaviour in the single mode MW cavity which was used for experimental work. In order to supply a valid methodology and tool for measuring the environmental impact, a comparative study between the synthetic route proposed and the classical synthetic route has been carried out. http://www.mdpi.com/1420-3049/12/7/1482/ Thu, 19 Jul 2007 00:00:00 CEST Molecules 2007-07-19 12 7 Article 1482 1495 1420-3049 New “Green” Approaches to the Synthesis of Pyrazole Derivatives 2007-07-19 doi: 10.3390/12071482 Anna Corradi Cristina Leonelli Antonino Rizzuti Roberto Rosa Paolo Veronesi Romano Grandi Sara Baldassari Carla Villa http://www.mdpi.com/1420-3049/12/7/1389/ The newly synthesized 5,10,15,20-tetra[3-(3-trifluoromethyl)phenoxy]porphyrin, TTFMPP, has been characterized using mass spectroscopy, 1H-, 13C- and 19F-NMR, MALDI-TOF mass spectrometry, UV-Vis and fluorescence spectrophotometry, andcyclic voltammetry. The NMR confirmed the structure of the compound and the massspectrum was in agreement with the proposed molecular formula. The UV-Vis absorptionspectrum of TTFMPP shows characteristic spectral patterns similar to those of tetraphenylporphryin, with a Soret band at 419 nm and four Q bands at 515, 550, 590, and 648 nm.Protonation of the porphyrin with TFA resulted in the expected red shift of the Soret band.Excitation at 419 nm gave an emission at 650 nm. The quantum yield of the porphyrin wasdetermined to be 0.08. Cyclic voltammetry was used to determine the oxidation andreduction potentials of the new porphyrin. Two quasi-reversible one-electron reductions at–1.00 and –1.32 V and a quasi-reversible oxidation at 1.20 V versus the silver/silverchloride reference electrode with tetrabutylammonium tetrafluoroborate as the supportingelectrolyte in methylene chloride were observed. http://www.mdpi.com/1420-3049/12/7/1389/ Wed, 11 Jul 2007 00:00:00 CEST Molecules 2007-07-11 12 7 Article 1389 1398 1420-3049 Atmospheric Pressure Microwave Assisted Heterogeneous Catalytic Reactions 2007-07-11 doi: 10.3390/12071389 Cynthia P Tidwell Prakash Bharara Gretchen Rudeseal Tiffany Rudeseal Frank H Rudeseal Christine A Simmer Dugald McMillan Katherine Lanier L Dalila Fondren LaTasha L Folmar Ken Belmore http://www.mdpi.com/1420-3049/12/5/1183/ Five optically active imidazole derivatives have been synthesized via a facile 4-step reaction sequence starting from commercially available and inexpensive N-Cbz amino acids. While microwave assisted condensation was unsuccessful, the condensation of the corresponding α-bromoketones with formamidine acetate in liquid ammonia was revealed to be a useful method for the synthesis of such imidazole derivatives. The derivatives thus prepared are structurally-related to histamine. http://www.mdpi.com/1420-3049/12/5/1183/ Wed, 30 May 2007 00:00:00 CEST Molecules 2007-05-30 12 5 Article 1183 1190 1420-3049 Facile Synthesis of Optically Active Imidazole Derivatives 2007-05-30 doi: 10.3390/12051183 Ales Marek Jiri Kulhanek Miroslav Ludwig Filip Bures http://www.mdpi.com/1420-3049/12/4/703/ Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants of the terrestrial environment that have been designated as Environmental Protection Agency (EPA) Priority Pollutants. In this study, molecular modeling was used to examine the physical and chemical characteristics of soil organic matter (SOM), fulvic acid (FA) and humic acid (HA), as well as their binding interactions with PAHs. The molecular structures of 18 PAHs were built by using the SYBYL 7.0 program and then fully optimized by a semiempirical (AM1) method. A molecular docking program, AutoDock 3.05, was used to calculate the binding interactions between the PAHs, and three molecular structure models including FA (Buffle’s model), HA (Stevenson’s model) and SOM (Schulten and Schnitzer’s model). The π-π interactions and H-bonding interactions were found to play an important role in the intermolecular bonding of the SOM/PAHs complexes. In addition, significant correlations between two chemical properties, boiling point (bp) and octanol/water partition coefficient (Log Kow) and final docking energies were observed. The preliminary docking results provided knowledge of the important binding modes to FA, HA and SOM, and thereby to predict the sorption behavior of PAHs and other pollutants. http://www.mdpi.com/1420-3049/12/4/703/ Thu, 05 Apr 2007 00:00:00 CEST Molecules 2007-04-05 12 4 Article 703 715 1420-3049 Investigation on the Binding of Polycyclic AromaticHydrocarbons with Soil Organic Matter: A Theoretical Approach 2007-04-05 doi: 10.3390/12040703 Patchreenart Saparpakorn Jae Hyoun Kim Supa Hannongbua http://www.mdpi.com/1420-3049/12/3/634/ 5-Acetoxymethyl- and 5-hydroxymethyl-2-vinylfuran were synthesized by two routes. The first route starts from 2-methylfuran and the second from furfuryl acetate. The latter route, involving successive Vilsmeier-Haack and Wittig reactions, is suitable for producing 5-acetoxymethyl-2-vinylfuran and 5-hydroxymethyl-2 vinylfuran in 68% and 60%yields, respectively. http://www.mdpi.com/1420-3049/12/3/634/ Mon, 26 Mar 2007 00:00:00 CEST Molecules 2007-03-26 12 3 Article 634 640 1420-3049 Synthesis of 5-Acetoxymethyl- and 5-Hydroxymethyl-2-vinyl-furan 2007-03-26 doi: 10.3390/12030634 Alexander Mehner Ana L Montero Ricardo Martinez Stefan Spange http://www.mdpi.com/1420-3049/12/3/504/ Selenium-containingheterocyclic compounds have been well recognized, not only because of their remarkable reactivities and chemical properties, but also because of their diverse pharmaceutical applications. In this context, isoselenocyanates have been emerged as a powerful tool for the synthesis of selenium-containing heterocycles, since they are easy to prepare and store and are safe to handle. In this review the recent advances in the development of synthesis methods forselenium-containing heterocycles from isoselenocyanates are presented and discussed. http://www.mdpi.com/1420-3049/12/3/504/ Sat, 17 Mar 2007 00:00:00 CET Molecules 2007-03-17 12 3 Review 504 535 1420-3049 Isoselenocyanates: A Powerful Tool for the Synthesis of Selenium-Containing Heterocycles 2007-03-17 doi: 10.3390/12030504 Dinesh Ramesh Garud Mamoru Koketsu Hideharu Ishihara http://www.mdpi.com/1420-3049/12/3/353/ Four new diterpenoid alkaloids: tiantaishansine (1), tiantaishannine (2), tiantaishanmine (3), and tiantaishandine (4) have been isolated from the roots of Delphinium tiantaishan. Their structures were elucidated by chemical evidence andspectral analyses, including ESI-MS, HR-EI-MS, 1D- and 2D-NMR. http://www.mdpi.com/1420-3049/12/3/353/ Thu, 08 Mar 2007 00:00:00 CET Molecules 2007-03-08 12 3 Article 353 360 1420-3049 New Diterpenoid Alkaloids from the Roots of Delphinium tiantaishanense 2007-03-08 doi: 10.3390/12030353 Jie Li Dong-Lin Chen Xi-Xian Jian Feng-Peng Wang http://www.mdpi.com/1420-3049/12/2/255/ Synthesis of 3,1,5-benzoxadiazepines from the condensation of o-phenylenediamine (o-PDA) and acyl chlorides in the presence of a catalytic amount of various heteropolyacids (HPAs) is reported. http://www.mdpi.com/1420-3049/12/2/255/ Mon, 26 Feb 2007 00:00:00 CET Molecules 2007-02-26 12 2 Article 255 262 1420-3049 Heteropolyacids as Green and Reusable Catalysts for the Synthesis of 3,1,5-Benzoxadiazepines 2007-02-26 doi: 10.3390/12020255 Majid M. Heravi Samaheh Sadjadi Hossein A. Oskooie Rahim Hekmat Shoar Fatemeh F. Bamoharram