1,1,3-Trimethyl-2-thioxo-l,2-dihydronaphthalene (1) adds to electron-rich olefins upon excitation to either S2 (ππ*) or S1 (nπ*) states. Excitation to S2 level resulted in the same mixture of products, namely thietane and 1,4-dithiane, as on excitation to S1 level. Addition occurs to the thiocarbonyl function and not to the carbon-carbon double bond. The addition is site-specific, and the formation of thietane is regiospecific. The ratio of thietane to 1,4-dithiane in the product mixture is dependent on the concentration of the thioenone. The addition is suggested to originate from the lowest triplet state (T1) and involves diradical intermediates.
ASJC Scopus subject areas
- Organic Chemistry