Strain-Assisted \alpha-Cleavage Reactions of Thioketones: Cyclobutanethiones

Photochemical \alpha -cleavage from the lowest triplet state $(n\pi^*, T_1)$, resulting in the generation of a diradical intermediate, appears to be general for cyclobutanethiones. The diradical intermediate derived from 1,3-dithione is observed to undergoes ring expansion to carbene or close to either dithione or dithiolactone. The Photochemical behavior reported here for cyclobutanethiones is different from that of the corresponding cyclobutanones. \alpha-Cleavage processes in the case of cyclobutanethiones are not efficient and are often accompanied by side reactions