Fumio Ishii

Photochemical reactions of 1,2,4-dithiazole-3-thione and 1,2-dithiole-3-thione with olefins

Photoreactions of 5-phenyl-1,2,4-dithiazole-3-thione (1) and of 5-phenyl-(2) and 4,5-diphenyldithiole-3-thione (3) with olefins lead to 2-thiobenzoylimino-(5), 2-thiobenzoylmethylene-(6), and 2-(α-thiobenzoylbenzylidene)-1,3-dithiolans (7), respectively, in good yields. The reactions are nonstereospecific with regard to the adding olefin, both cis- and trans-but-2-ene affording a mixture of two isomeric dithiolans (10) and (11) upon reaction with (2). The dithiazolethione (1) photochemically decomposes in the absence of olefin to give imidazole derivatives (13) and (14) while the dithiolethiones (2) and (3) are stable. A mechanism involving a diradical (20) is proposed.