Synlett 2012; 23(13): 1970-1972
DOI: 10.1055/s-0031-1290439
letter
© Georg Thieme Verlag Stuttgart · New York

A Novel Strategy for the Construction of Azole Heterocycles via an Oxidative Desulfurization Approach Using Iodobenzene and Oxone ®

Kavitkumar N. Patel
Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Matunga (E), Mumbai 400 019, India, Fax: +91(22)33611020   Email: vikastelvekar@rediffmail.com
,
Nikhil C. Jadhav
Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Matunga (E), Mumbai 400 019, India, Fax: +91(22)33611020   Email: vikastelvekar@rediffmail.com
,
Prashant B. Jagadhane
Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Matunga (E), Mumbai 400 019, India, Fax: +91(22)33611020   Email: vikastelvekar@rediffmail.com
,
Vikas N. Telvekar*
Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Matunga (E), Mumbai 400 019, India, Fax: +91(22)33611020   Email: vikastelvekar@rediffmail.com
› Author Affiliations
Further Information

Publication History

Received: 18 May 2012

Accepted after revision: 18 June 2012

Publication Date:
26 July 2012 (online)


Abstract

The oxidative desulfurization approach has been utilized for the construction of oxadiazole and thiadiazole heterocycles using iodobenzene and Oxone ® . The use of iodobenzene and the inexpensive readily available oxidant Oxone ® makes the reaction system simple and versatile for desulfurization.

 
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  • 6 Typical Procedure for the Oxidative Desulfurization A mixture of Oxone® (4 equiv) and iodobenzene (2 equiv) in MeOH was stirred at r.t. for 20 min followed by addition of Et3N (2 equiv) and substrate (1 equiv) at r.t. for 40 min. The reaction mixture was diluted with H2O and then extracted twice with EtOAc. The organic layer was washed succes-sively with 10% NaHCO3 (2 × 20 mL), H2O (2 × 20 mL) and dried over anhyd Na2SO4, filtered, and concen-trated under reduced pressure to give the crude product. The product was purified using silica gel column chromatography (30% EtOAc–hexane). N-(4-Bromophenyl)-5-(4-chlorophenyl)-2-amino-1,3,4-oxadiazole (2a) White solid, mp273–274 °C (lit.7a 272–274 °C). IR (KBr): 3318, 3032, 1551, 1435 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.49–7.53 (m, 4 H),7.61 (d, 2 H), 7.89 (d, 2 H), 4.10 (s, 1 H). N-5-Diphenyl-1,3,4-oxadiazole-2-amine (2i) White solid, mp 218–219 °C (lit.7a 217–219 °C). IR (KBr): 3371, 3043, 1549, 1452 cm–1. 1H NMR (300 MHz, DMSO-d 6): δ = 6.92 (t, 1 H), 7.33 (dd, 2 H), 7.41 (m, 3 H), 7.58–7.62 (m, 2 H), 7.89 (m, 2 H), 8.91 (s, 1 H, NH). N 2,N 5-Bis(4-methoxyphenyl)-1,3,4-thiadiazole-2,5-diamine (4a) White solid, mp 234–236 °C (lit.7b 235–237 °C). IR (KBr): 3328, 1543, 1436, 1053 cm–1. 1H NMR (300 MHz, DMSO-d 6): δ = 3.74 (s, 6 H), 7.04 (d, 4 H), 7.38 (d, 4 H), 8.21 (s, 2 H). N 2,N 5-Diphenyl-1,3,4-thiadiazole-2,5-diamine (4d) White solid, mp 238–240 °C (lit.7c 239–242 °C). IR (KBr): 3335, 1548, 1424, 1161 cm–1. 1H NMR (300 MHz, DMSO-d6 ): δ = 6.78 (d, 2 H), 7.15–7.47 (m, 6 H), 8.37 (s, 2 H).
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