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■ Cycloaddition of Benzothiazolium N-Phenacylide with Olefinic Dipolarophiles

Otohiko Tsuge,* Hiroshi Shimoharada, and Michiko Noguchi

*Graduate School of Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan

Abstract

Benzothiazolium N-phenacylide, generated in situ from 3-phenacylbenzothiazolium bromide and triethylamine, reacted with maleic anhydride, N-(p-methoxyphenyl)maleimide, dimethyl maleate, and fumrate to give the corresponding tetrahydropyrrolo[2,1-b]benzothiazole derivatives, all of which were stable on treatment with triethylamine, in good yields respectively. With maleonitrile the sole cycloadduct was formed, whereas fumaronitrile gave a mixture of two stereoisomeric cycloadducts. In some cases, dimer and/or hydrated compound of ylide were formed as by-products. On treatment with triethylamine epimerization and ring-transformation of cycloadducts obtained from both the dinitriles were observed.