Photocycloaddition of Benzothiazole-2-thiones to Alkenes

The photocycloaddition of benzothiazole-2-thiones to electron-rich and aryl-substituted alkenes are described. Irradiation of N-unsubstituted benzothiazole-2-thione (1) in the presence of alkenes 3 gave 2-(2′-mercaptoalkyl)benzothiazoles 4, and 2-substituted benzothiazoles 5 and 6 (in the case of 3a and 3h, resp.) through the ring cleavage of an intermediate 2-aminothietane (Schemes 1 and 3). The latter was formed by [2+2] cycloaddition of the CS bond of 1 and the CC bond of 3. Irradiation of N-methylbenzothiazole-2-thione (2) and 2-methylpropene (3a) gave the spiro-1,3-dithiane 8, 1,2,6-benzodithiazocin-5-one 9, and disulfide 10. The structure of 9 was established by X-ray crystal-structure analysis.

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