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Short Paper | Regular issue | Vol 94, No. 12, 2017, pp.2307-2316
Published online, 15th November, 2017
DOI: 10.3987/COM-17-13823
■ Synthesis of 3-(Alkylsulfanyl)-1,4-benzothiazine Derivatives Based on Cyclization of 2-[(Cyanomethyl)sulfanyl]phenyl Isothiocyanate

Kazuhiro Kobayashi,* Hiroki Inouchi, Ryo Hasegawa, and Kazuki Kawano

*Applied Chemistry Field, Chemistry and Biotechnology Course, Department of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan

Abstract

Efficient procedures for the preparation of 1,4-benzothiazine-based bicyclic and tricyclic heterocycles have been developed. The reaction of 2-[(cyanomethyl)sulfanyl]phenyl isothiocyanate, readily prepared from commercially available 2-aminobenzenethiol, with sodium hydride was found to give, after aqueous workup, 3-thioxo-3,4-dihydro-2H-1,4-benzothiazine-2-carbonitrile. Treatment with alkyl halides prior to workup yielded 3-(alkylsulfanyl)-4H-1,4-benzothiazine-2-carbonitriles. Successive treatment of these compounds with sodium hydride and alkyl halides afforded 4-alkyl-3-(alkylsulfanyl)-2H-1,4-benzothiazine-2-carbonitriles. These procedures can be applied to the synthesis of some 1,4-benzothiazine-based tricyclic heterocycles.