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Article

Synthesis of 1-(4-Trifluoromethoxyphenyl)-2,5-dimethyl-3-(2-R-thiazol-4-yl)-1H-pyrroles via Chain Heterocyclization

by
Mykhaylo V. Vovk
1,*,
Oleksandr M. Pinchuk
1,
Andrij O. Tolmachov
2 and
Andrei A. Gakh
3,*
1
Institute of Organic Chemistry, NAS of Ukraine, Murmanska 5, 02094 Kyiv, Ukraine
2
National Taras Shevchenko University, Volodymyrs`ka 62, 01033 Kyiv, Ukraine
3
Oak Ridge National Laboratory, Oak Ridge, TN 37831-6242, USA
*
Authors to whom correspondence should be addressed.
Molecules 2010, 15(2), 997-1006; https://doi.org/10.3390/molecules15020997
Submission received: 26 December 2009 / Revised: 22 February 2010 / Accepted: 22 February 2010 / Published: 23 February 2010
Browse Figures
Versions Notes

Abstract

:
The title compounds, (4-trifluoromethoxyphenyl)-2,5-dimethyl-3-(2-R-thiazol-4-yl)-1H-pyrroles, were prepared in four steps starting from commercially available 4-trifluoromethoxyaniline. The pyrrole (second ring) was added in one step using the Paal-Knorr method. The thiazole (third ring) was added in three steps using chloroacylation with chloroacetonitrile followed by heterocyclization with thioamides/thioureas.

1. Introduction

In the course of our search for new anti-cancer compounds that can be used in chemotherapy of late androgen-independent stages of prostate cancer, we turned our attention to the specific class of fluoroheterocyclic systems containing three linked rings, A-B-C, where B is a heterocyclic ring, and A and C are either a heterocyclic or an aromatic ring. Typically, these heterocyclic systems are produced by connecting of one heterocyclic and two aromatic or heterocyclic fragments together using appropriate linking methods. Unfortunately, many common linking procedures cannot be used for direct ring connections. An alternative approach entails chain heterocyclization where heterocyclic moieties are being added in one-by-one fashion using appropriate alicyclic components. Here we report the results of successful application of this strategy for the synthesis of A-B-C fluoroheterocyclic systems with pyrrole as the central unit B.
The pyrrole ring is a part of many natural compounds [1,2,3] as well as synthetic biologically active molecules [4,5]. For example, dialkylaminoalkyl esters of N-(4-hydroxyphenyl)pyrrole exhibit anesthetic and hypotensive properties [6], N-(3-carboxyphenyl)pyrroles are known as antiphlogistic compounds [7], and N-(4-phenoxyphenyl)pyrroles have anticholesteremic properties [8]. Some derivatives of 4-(2,5-dimethylpyrrolyl)benzoic acid inhibit Anthrax Lethal Factor (LF) [9] and Serotonin N-Acetyltransferase [10]. The trifluoromethoxy group is known for its utility in synthesis [11] and usefulness in the optimization of biologically active compounds [12,13,14,15]. Moreover, heterocyclic systems bearing the СF3O group are especially attractive, given their presence in, among others, the insecticide indoxacarb16], the acaricide flufenerim [17], the plant growth regulator flurprimidol [18], and the neurologic drug riluzole [19]. At the same time, little is known about heterocyclic systems containing CF3O-group(s) and pyrrole rings. Our research in this area started with the synthesis of 1-(4-trifluoromethoxyphenyl)-2,5-dimethyl-3-chloroacetylpyrrole - a new building block for the synthesis of extended heterocyclic libraries containing the 1-(4-trifluoromethoxyphenyl)pyrrole fragment [20].

2. Results and Discussion

The Paal-Knorr method [21] (which entails condensation of 1,4-diketones with anilines) is the most frequently used method for the synthesis of 1-aryl-2,5-dialkyl(aryl) substituted pyrroles. For example, 1-(4-trifluoromethoxyphenyl)-2,5-dimethylpyrrole (3) can be prepared in 76% yield from readily available 2,5-hexanedione (1) and 4-trifluoromethoxyaniline (2) by this route. According to the literature data [22,23], Friedel-Crafts acylation of 1-phenyl-2,5-pyrrole with alkylcarboxylic acid chlorides yields bis-acylated products (3,4-diketones), whereas acylation with aryl carboxylic acid chlorides results in a mixture of mono- (3-acylated) and bis- (3,4-acylated) products. It appears that direct acylation with chloroacetyl acid chloride cannot be used for selective preparation of the desired 3-chloroacetyl-2,5-dimethylpyrrole (5).
We developed a new preparative method for the synthesis of 3-chloroacetylpyrroles using mild and selective chloroacetylimidoyl chloride [24] that can be prepared in situ from chloroacetonitrile and hydrogen chloride. The desired iminium salt precipitates directly from the reaction mixture in 87% yield. Subsequent hydrolysis gives the target product 5 in 69 % yield (Scheme 1). The presence of a reactive chloroacetyl group in pyrrole 5 makes this compound an attractive building block for the preparation of various nitrogen-, oxygen- and sulfur-containing compounds containing a 4-trifluoromethoxyphenyl fragment. For example, N-alkylation of imidazole, isothiazole, tetrazole derivatives; O-alkylation of hetarylcarboxylic and hetarylacetic acids; S-alkylation of thiazole, 1,3,4-oxadiazole and tetrazole derivatives proceed easily and in mild conditions in DMSO or DMF solutions. The use of thioamides and thioureas in reactions with chloroacetylpyrrole (5) allowed us to add the desired third heterocyclic ring (thiazole fragment) as the last step of chain heterocyclization. As a result, new 4-trifluoromethoxyphenyl substituted pyrroles 6a-c, 7a-c, 8a-c, 9a-g functionalized with a set of pharmacophoric heterocyclic groups were successfully prepared using this approach (Scheme 2, Table 1).
Molecules 15 00997 g001 550
Scheme 1. Synthesis of 3-chloroacetylpyrrole (5).
Scheme 1. Synthesis of 3-chloroacetylpyrrole (5).
Molecules 15 00997 g001
Molecules 15 00997 g002 550
Scheme 2. Synthesis of 4-trifluoromethoxyphenyl substituted pyrroles 6-9 (R1-R5: see Table 1).
Scheme 2. Synthesis of 4-trifluoromethoxyphenyl substituted pyrroles 6-9 (R1-R5: see Table 1).
Molecules 15 00997 g002
Table
Table 1. Yields and melting points of the synthesized compounds.
Table 1. Yields and melting points of the synthesized compounds.
ProductRYield, %MpProductRYield, %Mp
6a Molecules 15 00997 i003 (R1R2N)76174-1758c Molecules 15 00997 i004 (SR4)92106
6b Molecules 15 00997 i005 (R1R2N)81232-2349aMe (R5)62134-135
6c Molecules 15 00997 i006 (R1R2N)70126-1279b2-Thienyl (R5)65115-116
7a Molecules 15 00997 i007 [OC(O)R3]71143-1449c Molecules 15 00997 i008 (R5)69131-132
7b Molecules 15 00997 i009 [OC(O)R3]74110-1119dNH2 (R5)71126-127
7c Molecules 15 00997 i010 [OC(O)R3]781039eMeNH (R5)64166-167
8a Molecules 15 00997 i011 (SR4)84132-1339f Molecules 15 00997 i012 (R5)70129-130
8b Molecules 15 00997 i013 (SR4)89165-1669g Molecules 15 00997 i014 (R5)65108-109

3. Experimental

3.1. General

Melting points were determined with a Kofler micro hot-stage (Reichert, Wien) and were uncorrected. 1H- and 19F-NMR spectra were recorded in DMSO-d6 on a Varian-Gemini spectrometer at 299.94 and 188.14 MHz, respectively, with TMS (1H) and CCl3F (19F) as internal standards. 13C-NMR spectra were recorded on a Bruker Arano DRX-500 spectrometer (125.75 MHz), with TMS as internal standard. APCI MS data were obtained on an Agilent 1100\DAD\MSD VL G1965a instrument.
2,5-Dimethyl-1(4-(trifluoromethoxyphenyl)-1H-pyrrole (3). A mixture of 4-trifluoromethoxyaniline (30 g, 170 mmol) and 2,5-hexanedione (22.8 g, 200 mmol) in acetic acid (150 mL) was refluxed for 4 h. The reaction mixture was cooled and poured into water (500 mL), the precipitated solid was filtered and dried. Yield 32.9 g (76 %); mp 68 °C; 1H-NMR: δ 1.98 (s, 6H), 5.76 (s, 2H), 7.34 (d, 2H, J = 9.0 Hz), 7.41 (d, 2H, J = 9.0 Hz); 13C-NMR: δ 12.66 (2 CH3), 106.18 (pyrrole, 3,4-C), 120.57 (q, CF3, J = 254.6 Hz), 121.64 (4-CF3O-C6H4, 3,5-C), 127.60 (pyrrole, 2,5-C), 129.90 (4-CF3O-C6H4, 2,6-C), 137.32 (4-CF3O-C6H4, 1-C), 147.33 (4-CF3O-C6H4, 4-C); 19F-NMR: δ -57.75 (F3CO); MS: m/z 256.0 (M+1)+; Anal. Calcd. for C13H12CF3NO: C 61.18; H 4.74; N 5.49. Found: C 61.31; H 4.77; N 5.61.
2-Chloro-1-{2,5-dimethyl-1-[(4-trifluoromethoxy)phenyl]-1H-pyrrol-3yl}-ethanimine hydrochloride (4). Dry hydrogen chloridewas bubbled through a solution of 2,5-dimethyl-1[4-(trifluoromethoxy)phenyl]-1H-pyrrole (32.9 g, 130 mmol ) and chloroacetonitrile (15 g, 200 mmol) in diethyl ether (200 mL) for 2 hours with vigorous stirring at 5-10 оС. The reaction mixture was left for 12 hours at room temperature. The precipitated solid was collected by filtration, washed with diethyl ether and dried in air. Yield 41.4 g (87 %); mp 220o C; 1H-NMR: δ 2.23 (s, 3H), 2.36 (s, 3H), 5.11 (s, 2H), 7.015 (s, 1H), 7.44 (d, 2H, J = 9.0 Hz), 7.51 (d, 2H, J = 9.0 Hz), 11.62 (s, 1H), 11.96 (s, 1H); 19F-NMR: δ - 57.14 (F3CO); Anal. Calcd. for C15H15Cl2F3NO2: C 49.07; H 4.19; Cl 19.31. Found: C 49.23; H 4.08; Cl 19.17.
2-Chloro-1-{2,5-dimethyl-1-[4-(trifluoromethoxy)phenyl]-1H-pyrrol-3-yl}-ethanone (5). A suspension of 2-chloro-1-{2,5-dimethyl-1-[(4-trifluoromethoxy)phenyl]-1H-pyrrol-3yl}-ethanimine hydrochloride (4, 41.4 g, 110 mmol) in water (200 mL) was heated under reflux for 1 h. The reaction mixture was cooled to room temperature; the precipitated solid was collected, washed with water, and dried. The product was crystallized from methanol. Yield 25.8 g (69 %); mp 147 oC;IR (KBr, cm-1) 1685; 1H- NMR: δ 1.94 (s, 3H), 2.22 (s, 3H), 4.75 (s, 2H), 6.48 (s, 1H), 7.49 (d, 2H, J = 9.0 Hz), 7.56 (d, 2H, J = 9.0 Hz); 13C-NMR: δ 12.28 (CH3), 12.49 (CH3), 47.80 (CH2), 107.40 (pyrrole, 4-C), 117.04 (pyrrole, C-5), 121.45 (q, CF3, J =257.8 Hz), 123.19 (4-CF3O-C6H4, 3,5-C), 128.73 (pyrrole, 3-C), 130.02 (4-CF3O-C6H4, 2,6-C), 135.35 (4-CF3O-C6H4, 1-C), 136.09 (pyrrole, 2-C), 148.15 (q, 4-CF3O-C6H4 , 4-C, J = 1.3 Hz), 186.80 (C=O); 19F-NMR: δ -56.89 (F3CO); MS: m/z 332.0 (M+1)+; Anal. Calcd. for C15H13ClF3NO2: C 54.31; H 3.95; N 4.22. Found: C 54.20; H 3.87; N 4.11.

3.2. General method for synthesis of 2,5-dimethyl-3-(2-N-substituted-1-oxoethyl)-1-[4-(trifluoro-methoxy)phenyl]-1H-pyrroles 6a-c

An appropriate heterocyclic compound (5 mmol) and triethylamine (1.0 mL, 7.5 mmol) were added to a solution of 2-сhloro-1-{2,5-dimethyl-1-[4-(trifluoromethoxy)phenyl]-1H-pyrrol-3-yl}-ethanone (5, 1.66 g, 5 mmol) in DMF (50 mL). The reaction mixture was heated at 75-80 °C with stirring for 2 h, and then it was cooled and poured into water (100 mL). The precipitated solid was filtrated and crystallized from dioxane.
1-{2-[2,5-Dimethyl-1(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-oxoethyl}-3-methylinidazolidine-2,4,5-trione (6a). 1H-NMR: δ 1.99 (s, 3H), 2.23 (s, 3H), 3.07 (s, 3H), 4.81 (s, 2H), 6.63 (s, 1H), 7.48 (d, 2H, J = 9.0 Hz), 7.54 (d, 2H, J = 9.0 Hz); 19F-NMR: δ - 57.47 (F3CO); MS: m/z 424.0 (M+1)+; Anal. Calcd. for C19H16F3N3O5: C 55.93; H 3.81; N 9.93. Found: C 56.04; H 3.88; N 9.80.
2-{2-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-oxoethyl}-1,1-dioxo-1,2-dihydro-1λ6-benzo[d]isothiazol-3-one (6b). 1H-NMR: δ 2.01 (s, 3H), 2.24 (s, 3H), 4.97 (s, 2H), 6.67 (s, 1H), 7.47 (d, 2H, J = 7.7 Hz), 7.53 (d, 2H, J = 8.8 Hz), 8.05 (m, 3H), 8.38 (d, 1H, J = 8.8 Hz); 19F-NMR: δ ‑ 57.44 (F3CO). MS: m/z 479.0 (M+1)+; Anal. Calcd. for C22H17F3N2O5S: C 55.23; H 3.58; N 5.86. Found: C 55.35; H 3.68; N 5.97.
1-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-[5-(3-methoxyphenyl)-tetrazol-2-yl]-ethanone (6c). 1H-NMR: δ 2.02 (s, 3H), 2.25 (s, 3H), 3.86 (s, 3H), 6.19 (s, 2H), 6.65 (s, 1H), 7.09 (dd, 1H, J = 7.4 Hz, J = 2.3 Hz), 7.59 (m, 7H). 19F-NMR: δ - 57.49 (F3CO); MS: m/z 472.0 (M+1)+; Anal. Calcd. for C23H20F3N5O3: C 58.60; H 4.28; N 14.86. Found: C 58.93; H 4.09; N 14.64.

3.3. General method for synthesis of2,5-dimethyl-3-(2-O-substituted 1-oxoethyl)-1-[4-(trifluoromethoxy)-phenyl]-1H-pyrroles 7 a-c

An appropriate acid (5 mmol) and potassium сarbonate (1.4 g, 10 mmol) were added to a solution of 2-сhloro-1-{2,5-dimethyl-1-[4-(trifluoromethoxy)phenyl]-1H-pyrrol-3-yl}-ethanone (5, 1.66 g, 5 mmol) in DMSO (50 mL). The reaction mixture was heated at 45-50оС with stirring for 4 h. The reaction mixture was cooled and poured into water (100 mL). The precipitated solid was collected, dried and recrystallized from 2-propanol.
3-Methylisoxazole-5-carboxylic acid 2-[2,5-dimethyl-1(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-oxoethyl ester (7a). IR (KBr, cm-1) 1700, 1775; 1H-NMR: δ 1.99 (s, 3H), 2.25 (s, 3H), 2.36 (s, 3H), 5.41 (s, 2H), 6.50 (s, 1H), 7.21 (s, 1H), 7.49 (d, 2H, J = 9.0 Hz), 7.54 (d, 2H, J = 9.0 Hz); 19F-NMR: - 57.47 (F3CO); MS: m/z 423.0 (M+1)+; Anal. Calcd. for C20H17F3N2O5: C 56.88; H 4.06; N 6.63. Found: C 56.79; H 4.10; N 6.59.
(5-Methylisoxazol-3-yloxy)acetic acid 2-[2,5-dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-oxoethyl ester (7b). IR (KBr, cm-1) 1695, 1770; 1H-NMR: δ 1.97 (s, 3H), 2.24 (s, 3H), 2.33 (s, 3H), 4.95 (s, 2H), 5.21 (s, 2H), 6.03 (s, 1H), 6.46 (s, 1H), 7.47 (d, 2H, J = 8.7 Hz), 7.52 (d, 2H, J = 8.7 Hz); 19F-NMR: - 57.50 (F3CO); MS: m/z 453.0 (M+1)+; Anal. Calcd. for C21H19F3N2O6: C 55.76; H 4.23; N 6.19. Found: C 55.65; H 4.24; N 6.12.
(2-Oxo-2H-pyridin-1-yl)acetic acid 2-[2,5-dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-oxoethyl ester (7c). IR (KBr, cm-1) 1670, 1695, 1770;1H-NMR: δ 1.96 (s, 3H), 2.23 (s, 3H), 4.86 (s, 2H), 5.22 (s, 2H), 6.27 (t, 1H, J = 5.4 Hz), 6.42 (d, 1H, J = 9.0 Hz), 6.49 (s, 1H), 7.46 (dd, 1H, J = 6.3 Hz, J = 2.1 Hz), 7.50 (d, 2H, J = 8.8 Hz), 7.57 (d, 2H, J = 8.8 Hz), 7.73 (dd, 1H, J = 5.1 Hz, J = 1.9 Hz); 19F-NMR: - 57.16 (F3CO); MS: m/z 449.2 (M+1)+; Anal. Calcd for C22H19F3N2O5: C 58.93; H 4.27; N 6.25. Found: C 58.82; H 4.24; N 6.16.

3.4. General method for synthesis of 2,5-dimethyl-3-(2-S-substituted 1-oxoethyl)-1-[4-(trifluoromethoxy)phenyl]-1H-pyrroles 8 a-c

An appropriate thione (5 mmol) and potassium сarbonate (1.4 g, 10 mmol) were added to a solution of2-сhloro-1-{2,5-dimethyl-1-[4-(trifluoromethoxy)phenyl]-1H-pyrrol-3-yl}-ethanone (5, 1.66 g, 5 mmol) in DMF (50 mL). The reaction mixture was heated at 65-70 °C with stirring for 2 h, and then it was cooled and poured into water (100 mL). The precipitated solid was collected, dried and recrystallized from ethanol/DMF 4:1.
1-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-([1,3,4]thiadiazol-2-ylsulfanyl)-ethanone (8a). 1H-NMR: δ 1.99 (s, 3H), 2.25 (s, 3H), 4.77 (s, 2H), 6.57 (s, 1H), 7.45 (d, 2H, J =7.6 Hz), 7.50 (d, 2H, J = 7.6 Hz), 9.50 (s,1H) 19F-NMR: - 57.50 (F3CO); MS: m/z 414.0 (M+1)+; Anal. Calcd. for C17H14F3N2O2S2: C 59.45; H 4.99; N 12.23 Found: C 59.58; H 4.91; N 12.32.
1-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-(5-[1,2,4]triazol-1-ylmethyl-[1,3,4]-oxadiazol-2-ylsulfanyl)ethanone (8b). 1H-NMR: δ 1.99 (s, 3H), 2.24 (s, 3H), 4.73 (s, 2H), 5.80 (s, 2H), 6.52 (s, 1H), 7.49 (d, 2H, J = 9.0 Hz), 7.52 (d, 2H, J = 9.0 Hz), 7.95 (s, 1H), 8.60 (s, 1H). 19F-NMR: - 57.47 (F3CO); MS: m/z 479.0 (M+1)+; Anal. Calcd. for C20H17F3N6O3S: C 50.21; H 3.58; N 17.56. Found: C 50.32; H 3.52; N 17.63.
1-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-(1-methyl-1H-tetrazol-5-ylsulfanyl)ethanone (8c). 1H NMR (DMSO-d6): δ 1.99 (s, 3H), 2.24 (s, 3H), 4.00 (s, 3H), 4.75 (s, 2H), 6.54 (s, 1H), 7.47 (d, 2H, J = 9.0 Hz), 7.53 (d, 2H, J = 9.0 Hz). 19F NMR (DMSO-d6): - 57.47 (F3CO). MS: m/z 412.0 (M+1)+. Anal. Calcd. for C17H16F3N5O2S: C 49.63; H 3.92; N 17.02. Found: C 49.75; H 3.82; N 17.13.

3.5. General method for synthesis of 4-[2,5-dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]thiazoles 9a-g

A mixture of 2-сhloro-1-{2,5-dimethyl-1-[4-(trifluoromethoxy)phenyl]-1H-pyrrol-3-yl}-ethanone (5, 1.66 g, 5 mmol) and thioamide/thiourea (5 mmol) in ethanol (40 mL) was refluxed for 5 h. The solid separated on cooling was collected by filtration, dried and recrystallized from ethanol.
4-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-methylthiazole (9a). 1H-NMR: δ 2.00 (s, 3H), 2.25 (s, 3H), 2.67 (s, 3H), 6.24 (s, 1H), 7.15 (s, 1H), 7.44 (d, 2H, J = 9.0 Hz), 7.50 (d, 2H, J = 9.0 Hz); 19F-NMR: - 57.43 (F3CO); MS: m/z 353.0 (M+1)+; Anal. Calcd. for C17H15F3N2OS: C 57.95; H 4.29; N 7.95. Found: C 57.86; H 4.21; N 8.04.
4-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]-2-thiophen-2-ylthiazole (9b). 1H-NMR: δ 2.03 (s, 3H), 2.32 (s, 3H), 6.35 (s, 1H), 7.12 (t, 1H, J = 5.6 Hz), 7.20 (s, 1H), 7.42 (d, 2H, J = 8.7 Hz), 7.47 (d, 2H, J = 8.7 Hz), 7.70 (m, 2H); 19F-NMR (DMSO-d6): - 57.69 (F3CO); MS: m/z 421.0 (M+1)+; Anal. Calcd. for C20H15F3N2OS2: C 57.13, H 3.60; N 6.66. Found: C 57.19; H 3.55; N 6.74.
2-{4-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]thiazol-2-yl}-N-phenylacetamide (9c). 1H-NMR: δ 1.99 (s, 3H), 2.24 (s, 3H), 4.25 (s, 2H), 6.28 (s, 1H), 7.03 (t, 1H, J =7.6 Hz), 7.31 (m,2H) 7.41 (s, 1H), 7.48 (d, 2H, J =9.0 Hz), 7.52 (m, 2H), 7.64 (d, 2H, J =9.0 Hz), 10.55 (s,1H); 19F-NMR: - 57.43 (F3CO). MS: m/z 472.0 (M+1)+; Anal. Calcd. for C24H20F3N3O2S: C 61.14, H 4.28; N 8.91. Found: C 61.29; H 4.21; N 8.84.
4-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]thiazol-2-ylamine (9d). 1H-NMR: δ 2.02 (s, 3H), 2.12 (s, 3H), 6.27 (s, 1H), 6.49 (s, 1H), 7.43 (d, 2H, J = 8.7 Hz), 7.48 (d, 2H, J = 8.7 Hz), 9.10 (br s, 2H). 19F-NMR: - 57.70 (F3CO). MS: m/z 354.0 (M+1)+; Anal. Calcd. for C16H14F3N3OS: C 54.38; H 3.99; N 11.89. Found: C 54.46; H 4.07; N 11.80.
{4-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]thiazol-2-yl}methylamine (9e). 1H- NMR: δ 1.90 (s, 3H), 2.25 (s, 3H), 3.00 (s, 3H), 6.24 (s, 1H), 6.65 (s, 1H), 7.45 (d, 2H, J = 9.0 Hz), 7.51 (d, 2H, J = 9.0 Hz), 9.34 (br s, 1H); 19F-NMR: - 57.43 (F3CO). MS: m/z 368.0 (M+1)+; Anal. Calcd. for C17H16F3N3OS: C 55.58; H 4.39; N 11.44. Found: C 55.67; H 4.31; N 11.50.
{4-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]thiazol-2-yl}-(2-methoxyethyl)amine (9f). 1H-NMR: δ 1.99 (s, 3H), 2.24 (s, 3H), 3.29 (s, 3H), 3.43 (t, 2H, J = 5.4 Hz), 3.52 (t, 2H, J = 5.4 Hz), 6.12 (s, 1H), 6.23 (s, 1H), 7.40 (d, 2H, J = 9.0 Hz), 7.48 (d, 2H, J =9.0 Hz); 19F-NMR: - 57.70 (F3CO); MS: m/z 412.0 (M+1)+; Anal. Calcd for C19H20F3N3O2S: C 55.47; H 4.80; N 10.21. Found: C 55.58; H 4.79; N 10.09.
{4-[2,5-Dimethyl-1-(4-trifluoromethoxyphenyl)-1H-pyrrol-3-yl]thiazol-2-yl}-(tetrahydrofuran-2-yl-methyl)amine (9g). 1H-NMR: δ 1.62 (m, 1H), 1.73 (m,2H), 1.85 (m, 1H), 1.96 (s, 3H), 2.23 (s, 3H), 3.25 (s,2H), 3.64 (m, 1H), 3.77 (m, 1H), 4.03 (m, 1H), 6.13 (s, 1H), 6.27 (s, 1H), 7.41 (d, 2H, J = 8.7 Hz), 7.47 (d, 2H, J = 8.7 Hz), 8.56 (m, 1H); 19F-NMR: - 57.47 (F3CO); MS: m/z 438.0 (M+1)+; Anal. Calcd for C21H22F3N3O2S: C 57.66; H 4.5.07; N 9.60. Found: C 57.79; H 5.09; N 9.49.

4. Conclusions

In summary, we developed a successful chain heterocyclization strategy for the synthesis of A‑B‑C fluoroheterocyclic systems with pyrrole as the central unit B. These compounds were prepared in four steps starting from commercially available 4-trifluoromethoxyaniline. The pyrrole ring was added in one step using Paal-Knorr method, and the third thiazole ring was added in three steps using chloroacylation with cloroacetonitrile followed by heterocyclization with thioamide/thiourea. We are currently evaluating biological profiles of these new fluorinated heterocyclic systems.

Acknowledgements

This research was supported by the Global IPP program through the Science and Technology Center in Ukraine (STCU). Oak Ridge National Laboratory is managed and operated by UT-Battelle, LLC, under U.S. Department of Energy contract DE-AC05-00OR22725. This paper is a contribution from the Discovery Chemistry Project.

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  • Sample Availability: Samples of the compounds are available from the authors.

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MDPI and ACS Style

Vovk, M.V.; Pinchuk, O.M.; Tolmachov, A.O.; Gakh, A.A. Synthesis of 1-(4-Trifluoromethoxyphenyl)-2,5-dimethyl-3-(2-R-thiazol-4-yl)-1H-pyrroles via Chain Heterocyclization. Molecules 2010, 15, 997-1006. https://doi.org/10.3390/molecules15020997

AMA Style

Vovk MV, Pinchuk OM, Tolmachov AO, Gakh AA. Synthesis of 1-(4-Trifluoromethoxyphenyl)-2,5-dimethyl-3-(2-R-thiazol-4-yl)-1H-pyrroles via Chain Heterocyclization. Molecules. 2010; 15(2):997-1006. https://doi.org/10.3390/molecules15020997

Chicago/Turabian Style

Vovk, Mykhaylo V., Oleksandr M. Pinchuk, Andrij O. Tolmachov, and Andrei A. Gakh. 2010. "Synthesis of 1-(4-Trifluoromethoxyphenyl)-2,5-dimethyl-3-(2-R-thiazol-4-yl)-1H-pyrroles via Chain Heterocyclization" Molecules 15, no. 2: 997-1006. https://doi.org/10.3390/molecules15020997

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