One-pot synthesis of 1-substituted 1H-1,2,3,4-tetrazoles from 2aminothiazoles using tributylmethylammonium chloride as a catalyst
-
Kerru Nagaraju
,
Gummidi Lalitha
Abstract
Reaction between substituted thiazolylamine or oxazolylamine, triethyl orthoformate and sodium azide in the presence of tributylmethylammonium chloride in DMSO furnishes 1-substituted 1H-1,2,3,4-tetrazole in high yield.
Introduction
Application of tetrazole compounds including 1-substituted tetrazoles has increased quickly over the past few years [1], [2], [3]. They have been used in medicinal chemistry, agriculture, coordination chemistry and the synthesis of nitrogen containing compounds [4]. Tetrazole moiety is a metabolically stable equivalent of carboxyl and amide groups in the molecules of peptidomimetics [5]. Many 1-substituted tetrazole derivatives are used as antibiotics [6]. While various 5-substituted tetrazoles have been widely reported, their 1-substituted analogs are rare [7], [8]. In general, they can be synthesized by the cycloaddition between isocyanides and trimethyl azide/hydrazoic acid [9], [10] and by cyclization of ammonium salts with ortho carboxylic esters or hydrazoic acid metal salts, in addition to other methods [11], [12], [13], [14], [15], [16], [17], [18], [19]. Many tetrazole derivatives have been synthesized using ionic liquids as part of green synthesis [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33]. Herein we report a new synthesis of 1-substituted-1H-1,2,3,4-tetrazoles by one-pot condensation of sodium azide, substituted thiazolylamine or oxazolylamine and triethyl orthoformate in the presence of tributylmethylammonium chloride (TBMAC) as a catalyst in DMSO.
Results and discussion
The synthesis of diverse compounds 3a–k is outlined in Scheme 1. Under optimized conditions, a mixture of triethyl orthoformate (1, 1.5 mmol), one of the amines 2a–k (1.2 mmol), sodium azide (1.2 mmol), DMSO (5 mL) and TBMAC (2 mol%) was heated at 80°C for a period indicated in Experimental. The starting amines 2 were readily available commercial materials or easily synthesized according to the reported procedures [34], [35], [36], [37], [38]. The presence of TBMAC is essential for the success of the reaction. In the absence of TBMAC the product was isolated in a low yield after a long reaction time. By increasing the amount of the catalyst from 1.0 mol% to 1.5 mol% the yield of the product increased from 82% to 90%. A further increase in the amount of the catalyst to 2.0 mol%, the yield increased marginally from 90% to 94%. For the mechanism of a related reaction, see ref. [38].
Synthesis of 1-substituted-1H-1,2,3,4-tetrazoles 3a–k.
Conclusion
A convenient protocol for the synthesis of 1-substituted-1H-1,2,3,4-tetrazoles was developed.
Experimental
Melting points were determined in open capillaries on a Mel-Temp apparatus and are uncorrected. All reactions were monitored by thin layer chromatography (TLC) using silica gel 60 F254 and spots were visualized with UV light. Silica gel (60–120 mesh) was used for column chromatography. The IR spectra were recorded on a Perkin-Elmer BX1 FTIR spectrophotometer using KBr pellets. NMR spectra were recorded in CDCl3/DMSO-d6 solution on a Bruker AMX 400 spectrometer operating at 400 MHz for 1H and 100 MHz for 13C. The mass spectra were recorded on an Agilent 1100 LC/MSD instrument operating at 70 eV. Elemental analyses were obtained on a Thermo Finnigan Flash EA 1112 analyzer.
General procedure for preparation of 1-substituted- 1H-1,2,3,4-tetrazoles 3a–k
A mixture of the amine 2a–k (1.2 mmol), triethyl orthoformate (1.5 mmol), sodium azide (1.2 mmol), DMSO (5 mL) and TBMAC (2 mol%) was stirred at 80°C. The progress of the reaction was monitored by TLC eluting with a mixture of n-hexane and ethyl acetate (3.5:1.5). After completion of the reaction, the mixture was treated with crushed ice. The precipitated product was filtered, washed with water, dried and purified by silica gel column chromatography using EtOAc/hexane as eluent to afford pure product 3a–k.
4-Chloro-2-(1H-tetrazol-1-yl)benzo[d]thiazole (3a)
This compound was obtained from 4-chlorobenzo[d]thiazol-2-amine; reaction time 90 min; yield 94%; white solid; mp 206–208°C; IR (νmax/cm−1): 1651, 1583, 1470, 1173, 773; 1H NMR: δ 7.25 (t, J=10.4 Hz, 1H, Ar-H), 7.48 (d, J=12.0 Hz, 1H, Ar-H), 7.90 (d, J=12.0 Hz, 1H, Ar-H), 8.77 (s, 1H, tetrazole-CH); 13C NMR: δ 121.6, 126.4, 134.8, 138.7, 146.1, 154.2, 155.9, 161.1; MS: m/z 238 (M+H)+. Anal. Calcd for C8H4ClN5S: C, 40.43; H, 1.70; N, 29.47. Found: C, 40.39; H, 1.76; N, 29.38.
5-Nitro-2-(1H-tetrazol-1-yl)benzo[d]thiazole (3b)
This compound was obtained from 5-nitrobenzo[d]thiazol-2-amine; reaction time 80 min; yield 92%; white fine powder; mp 196–198°C; IR (νmax/cm−1): 1663, 1543, 1442, 1209; 1H NMR: δ 7.33–7.36 (t, J=2.8 Hz, 1H, Ar-H), 7.64 (d, J=12.0 Hz, 1H, Ar-H), 7.96 (d, J=4.0 Hz, 1H, Ar-H), 8.76 (s, 1H, tetrazole-CH); 13C NMR: δ 125.4, 133.8, 137.7, 145.0, 151.3, 153.2, 154.9, 160.1; MS: m/z 249 (M+H)+. Anal. Calcd for C8H4N6O2S: C, 38.71; H, 1.62; N, 33.86. Found: C, 38.75; H, 1.69; N, 33.94.
5-Chloro-2-(1H-tetrazol-1-yl)benzo[d]thiazole (3c)
This compound was obtained from 5-chlorobenzo[d]thiazol-2-amine; reaction time 80 min; yield 86%; creamy solid; mp 192–194°C; IR (νmax/cm−1): 1642, 1562, 1432, 1184; 1H NMR: δ 7.66 (d, J=12.0 Hz, 1H, Ar-H), 7.80 (d, JHH=12.0 Hz, 1H, Ar-H), 8.27–8.30 (dd, J=2.4 and 2.0 Hz, 1H, Ar-H), 8.59 (s, 1H, tetrazole-CH); 13C NMR: δ 121.3, 130.3, 134.5, 138.3, 145.7, 153.8, 155.5, 160.8; MS: m/z 238 (M+H)+. Anal. Calcd for C8H4ClN5S: C, 40.43; H, 1.70; N, 29.47. Found: C, 40.46; H, 1.79; N, 29.55.
2-(1H-Tetrazol-1-yl)benzo[d]thiazole (3d)
This compound was obtained from benzo[d]thiazol-2-amine; reaction time 60 min; yield 85%; yellow solid; mp 218–220°C; IR (νmax/cm−1): 1631, 1553, 1412, 1185; 1H NMR: δ 7.21–7.24 (t, J=2.8 and 2.8 Hz, 1H, Ar-H), 7.41 (s, 1H, tetrazole-CH), 7.82 (d, J=12.0 Hz, 1H, Ar-H), 7.97 (d, J=12.0 Hz, 1H, Ar-H), 8.23 (d, J=12.0 Hz, 1H, Ar-H); 13C NMR: δ 125.8, 128.3, 144.0, 150.9, 153.0, 159.9, 161.0, 170.3; MS: m/z 204 (M+H)+. Anal. Calcd for C8H5N5S: C, 47.28; H, 2.48; N, 34.46. Found: C, 47.32; H, 2.57; N, 34.59.
5-Methyl-2-(1H-tetrazol-1-yl)benzo[d]thiazole (3e)
This compound was obtained from 5-methylbenzo[d]thiazol-2-amine; reaction time 80 min; yield 81%; white solid; mp 208–210°C; IR (νmax/cm−1): 2883, 1619, 1534, 1420, 1172; 1H NMR: δ 6.82–6.92 (dd, J=2.4 and 2.8 Hz, 1H, Ar-H), 7.09 (s, 1H, tetrazole-CH), 7.47 (d, J=12.0 Hz, 1H, Ar-H), 7.91 (d, J=12.0 Hz, 1H, Ar-H); 13C NMR: δC 20.1, 129.8, 134.0, 137.8, 145.2, 151.5, 153.3, 155.1, 160.3; MS: m/z 218 (M+H)+. Anal. Calcd for C9H7N5S: C, 49.76; H, 3.25; N, 32.24. Found: C, 49.72; H, 3.19; N, 32.15.
2-(1H-tetrazol-1-yl)benzo[d]oxazole (3f)
This compound was obtained from benzo[d]oxazol-2-amine; reaction time 80 min; yield 83%; creamy solid; mp 176–178°C; IR (νmax/cm−1): 1636, 1592, 1514, 1148; 1H NMR: δ 7.53 (t, J=8.4 Hz, 1H, Ar-H), 7.69 (d, J=11.6 Hz, 1H, Ar-H), 7.83 (d, J=10.8 Hz, 1H, Ar-H), 8.27–8.30 (dd, J=2.0 and 2.4 Hz, 1H, Ar-H), 8.83 (s, 1H, tetrazole-CH); 13C NMR: δ 109.7, 123.3, 125.4, 126.8, 129.4, 136.4, 138.0, 153.0; MS: m/z 188 (M+H)+. Anal. Calcd for C8H5N5O: C, 51.34; H, 2.69; N, 37.42. Found: C, 51.39; H, 2.76; N, 37.38.
4-(4-Methoxyphenyl)-2-(1H-tetrazol-1-yl)thiazole (3g)
This compound was obtained from 4-(4-methoxyphenyl)thiazol-2-amine; reaction time 75 min; yield 82%; white solid; mp 210–212°C; IR (νmax/cm−1): 2879, 1611, 1498, 1458, 1117; 1H NMR: δ 3.85 (s, 1H, OCH3), 7.51 (d, J=8.0 Hz, 2H, Ar-H), 8.20 (d, J=8.0 Hz, 2H, Ar-H), 8.48 (s, 1H, thiazole-CH), 8.77 (s, 1H, tetrazole-CH); 13C NMR: δ 51.2, 107.0, 120.9, 125.0, 131.8, 145.1, 150.9, 154.5, 159.8; MS: m/z 260 (M+H)+. Anal. Calcd for C11H9N5OS: C, 50.95; H, 3.50; N, 27.01. Found: C, 50.88; H, 3.42; N, 27.12.
4-(4-Bromophenyl)-2-(1H-tetrazol-1-yl)thiazole (3h)
This compound (available from several commercial sources) was obtained from 4-(4-bromophenyl)thiazol-2-amine; reaction time 90 min; yield 91%; yellow solid; mp 182–184°C; IR (νmax/cm−1): 1635, 1562, 1412, 1128; 1H NMR: δ 7.74 (d, J=12.0 Hz, 2H, Ar-H), 8.13 (s, 1H, thiazole-CH), 8.33 (d, J=12.0 Hz, 2H, Ar-H), 9.04 (s, 1H, tetrazole-CH); 13C NMR: δ 107.8, 110.4, 125.9, 145.9, 151.8, 153.6, 155.4, 160.6; MS: m/z 308 (M+H)+.
4-Phenyl-2-(1H-tetrazol-1-yl)thiazole (3i)
This compound (available from several commercial sources) was obtained from 4-phenylthiazol-2-amine; reaction time 70 min; yield 90%; yellow solid; mp 230–232°C; IR (νmax/cm−1): 1627, 1506, 1425, 1209; 1H NMR: δ 7.20 (s, 1H, thiazole-CH), 8.53–8.61 (m, 3H, Ar-H), 8.69 (t, J=12.0 Hz, 2H, Ar-H), 9.32 (s, 1H, tetrazole-CH); 13C NMR: δ 107.3, 108.7, 111.1, 126.0, 152.9, 153.6, 155.3, 160.6; MS: m/z 230 (M+H)+.
2-(1H-Tetrazol-1-yl)thiazole (3j)
This compound was obtained from thiazol-2-amine; reaction time 80 min; yield 94%; white solid; mp 148–150°C; IR (νmax/cm−1): 1661, 1543, 1409, 1112; 1H NMR: δ 7.31 (d, J=8.0 Hz, 1H, Ar-H), 7.63 (d, J=8.0 Hz, 1H, Ar-H), 9.12 (s, 1H, tetrazole-CH); 13C NMR: δC 128.6, 144.3, 151.1, 153.2; MS: m/z 154 (M+H)+. Anal. Calcd for C4H3N5S: C, 31.37; H, 1.97; N, 45.72. Found: C, 31.42; H, 1.90; N, 45.86.
5-Methyl-2-(1H-tetrazol-1-yl)thiazole (3k)
This compound was obtained from 5-methylthiazol-2-amine; reaction time 75 min; yield 76%; yellow solid; mp 160–162°C; IR (νmax/cm−1): 2891, 1637, 1551, 1423, 1164; 1H NMR: δ 1.86 (s, CH3), 7.48 (s, 1H, Ar-H), 8.96 (s, 1H, tetrazole-CH); 13C NMR: δ 17.6, 110.8, 125.8, 152.6, 153.3; MS: m/z 168 (M+H)+. Anal. Calcd for C5H5N5S: C, 35.92; H, 3.01; N, 41.89. Found: C, 35.98; H, 3.04; N, 41.84.
Acknowledgments
The authors are thankful to the authorities of the School of Chemistry and Physics, University of KwaZulu-Natal, Westville campus, Durban, South Africa and the Department of Chemistry, SV University, Tirupati, India for partial support of this work.
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Articles in the same Issue
- Frontmatter
- Review
- Chemical constituents from the genus Saussurea and their biological activities
- Preliminary Communication
- A new imidazoline-containing Bunte salt: synthesis, molecular and electronic structure
- Research Articles
- One-pot synthesis of 1-substituted 1H-1,2,3,4-tetrazoles from 2aminothiazoles using tributylmethylammonium chloride as a catalyst
- A new method for the synthesis of 4H-1,3,5-oxadiazine derivatives
- Simple access to spirooxadiazole compounds containing a quinoxaline moiety using a nitrile imine intermediate generated in situ
- A convenient regioselective synthesis of spirooxindolinopyrrolizidines incorporating the pyrene moiety through a [3 + 2]-cycloaddition reaction
- An efficient green synthesis of 5H-spiro[benzo[4,5]imidazo[1,2-c]quinazoline-6,3′-indolin]-2′-ones catalyzed by iodine in ionic liquids
- A selective fluorescence probe based on benzothiazole for the detection of Cr3+
- Spectrophotometric and quantum-chemical study of acid-base and complexing properties of (±)-taxifolin in aqueous solution
- Preparation of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones using ZrO2 nanoparticles as a catalyst under solvent-free conditions
- Microwave-assisted synthesis of bis(N-substituted thiazol-2-amine) derivatives and their biological activities
