Synlett 2012; 23(15): 2219-2222
DOI: 10.1055/s-0032-1317080
letter
© Georg Thieme Verlag Stuttgart · New York

A Novel System for the Synthesis of 2-Aminobenzthiazoles using Sodium Dichloroiodate

Vikas N. Telvekar*
Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Matunga, Mumbai 400 019, India, Fax: +91(22)24145614   Email: vikastelvekar@rediffmail.com
,
Harshal M. Bachhav
Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Matunga, Mumbai 400 019, India, Fax: +91(22)24145614   Email: vikastelvekar@rediffmail.com
,
Vinod Kumar Bairwa
Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Matunga, Mumbai 400 019, India, Fax: +91(22)24145614   Email: vikastelvekar@rediffmail.com
› Author Affiliations
Further Information

Publication History

Received: 18 May 2012

Accepted after revision: 19 July 2012

Publication Date:
17 August 2012 (online)


Abstract

2-Aminobenzthiazole is a privileged scaffold with a range of biological activities. However, to date, an efficient protocol for the synthesis of this ring system using aniline as a starting material has been lacking. Herein, for the first time, we describe a highly efficient and mild protocol for the synthesis of 2-aminiobenzthiazole using NaICl2.

 
  • References and Notes

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  • 15 General procedure for synthesis of 6-chloro-2-aminobenzthiazole (Table 2, entry 1): To a stirred solution of 4-chloroaniline (0.1 g, 0.78 mmol) and potassium thiocyanate (0.53 g, 5.5 mmol) in DMSO–H2O (9:1 mL) was added NaICl2 (2 M, 0.52 g, 2.3 mmol). The reaction mixture was stirred vigorously at r.t. for 5 min, then the mixture was heated to 70 °C and progress of the reaction was monitored by TLC. The reaction was quenched with H2O (10 mL) and extracted with EtOAc (3 × 10 mL). The organic phases were separated and washed successively with 10% aq Na2S2O4 (2 × 10 mL), 10% aq NaHCO3 (2 × 15 mL), and finally with H2O (2 × 20 mL). The organic layer was dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give the crude product. Pure 6-chloro-2-aminobenzthiozole was obtained as a yellow solid after silica gel column chromatography (EtOAc–hexane, 80:20). 1,3-Benzothiazol-2-amine (Table 3, entry 1) Mp 127–129 °C (Lit.16a 129–130 °C); IR (KBr): 3402, 3266, 3052, 1637, 1525, 1442, 1306, 1102 cm–1; 1H NMR (300 MHz, CDCl3): δ = 7.73–7.60 (m, 4 H), 5.70 (s, 2 H). Anal. Calcd for C7H6N2S: C, 55.97; H, 4.03; N, 18.65. Found: C, 55.99; H, 4.04; N, 18.62. 6-Methyl-1,3-benzothiazol-2-amine (Table 3, entry 2) Mp 132–133 °C (Lit.16b 135–137 °C); IR (KBr): 3373, 3285, 3072, 2934, 1637, 1535, 1458, 1374, 1302, 1107 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.63–7.50 (m, 3 H), 5.49 (s, 2 H), 2.51 (s, 3 H). Anal. Calcd for C8H8N2S: C, 58.51; H, 4.91; N, 17.06. Found: C, 58.47; H, 4.93; N, 17.08. 4,5-Dichloro-1,3-benzothiazol-2-amine (Table 3, entry 8) Mp 274–277 °C (Lit.16c 275–276 °C); IR (KBr): 3403, 3326, 3221, 1629, 1571, 1460, 1380, 810, 580 cm–1; 1H NMR (300 MHz, CDCl3): δ = 7.48–7.36 (m, 2 H), 6.78 (s, 2 H). Anal. Calcd for C7H4Cl2N2S: C, 38.37; H, 1.84; N, 12.79. Found: C, 38.39; H, 1.85; N, 12.76. 6-Nitro-1,3-benzothiazol-2-amine (Table 3, entry 11) Mp 245–247 °C (Lit.16d 247–248 °C); IR (KBr): 3452, 3298, 3047, 1652, 1566, 1528, 1494, 1325 cm–1; 1H NMR (300 MHz, CDCl3): δ = 8.20–8.12 (m, 3 H), 5.90 (s, 2 H). Anal. Calcd for C7H5N3O2S: C, 43.07; H, 2.58; N, 21.53. Found: C, 43.02; H, 2.59; N, 21.57. 6-(Trifluoromethyl)-1,3-benzothiazol-2-amine (Table 3, entry 14) Mp 119–122 °C (Lit.16e 122 °C); IR (KBr): 3461, 3221, 1634, 1600, 1480, 1441, 1340, 1263, 1167, 1128 cm–1; 1H NMR (300 MHz, CDCl3): δ = 7.70–7.62 (m, 3 H), 4.32 (s, 2 H). 4-Methoxy-1,3-benzothiazol-2-amine (Table 3, entry 17) Mp 148–153 °C (Lit.16f 149–151 °C); IR (KBr): 3379, 3283, 3091, 2937, 1636, 1545, 1458, 1333, 1270, 1049 cm–1; 1H NMR (300 MHz, CDCl3): δ = 7.37–7.10 (m, 3 H), 5.45–5.10 (br s, 2 H), 3.84 (s, 3 H). Anal. Calcd for C8H8N2OS: C, 53.31; H, 4.47; N, 15.54. Found: C, 53.26; H, 4.48; N, 15.58