Thiocoumarin upon photolysis adds to both electron-rich and -deficient olefins from the lowest triplet state to yield thietane and in some cases 1,4-dithiane. Although the rate of primary interaction between the triplet thiocoumarin and the olefin is high, the quantum yield of the adduct formation is low. A biradical and an exciplex are presumed to be involved as intermediates in the addition process. The observed behavior, although different from that of coumarin, follows largely the general cycloaddition pattern reported thus far for diaryl, dialkyl, and α,β-unsaturated thiones.
ASJC Scopus subject areas
- Organic Chemistry