Photochemistry of phospholens. Part 7. Element effects on the photofragmentation of 3,4-dimethyl-1-phenyl-3-phospholen. Phosphinothioylidene

Abstract

Photolysis of 3,4-dimethyl-1-phenyl-3-phospholen 1-sulphide (1) in methanol afforded, in addition to the expected diene, O-methyl phenyphosphinothioate (3) and OO-dimethyl phenylphosphonothioate (4), whose composition was dependent on irradiation time. Compound (4) was shown to be a photolysis product of (3) in methanol. The rate and stereospecificities of the photo-extrusion of (2) are investigated and compared with that observed in the photofragmentation of the corresponding oxide. In proceeding from the oxide to the sulphide, the stereo-specificities decreased in cis-α-methyl derivatives but increased in trans-α-methyl derivatives and the relative reactivities of the fragmentation decreased.