Oxathiirans as intermediates in the photolysis of sulphines

Abstract

Irradiation of thiobenzophenone S-oxide (8) in the region corresponding to its long-wavelength absorption (λ_max. 329 nm), in various solvents at room temperature, gave benzophenone in quantitative yield. At 85 K the photolytic transformation was monitored by electronic absorption spectroscopy. In EPA glass or PVC film a monomeric compound (390) with a long-wavelength absorption at 390 nm was formed. Heating gave rise to benzophenone in quantitative yield. On irradiation of (390) in its long-wavelength absorption region, a monomeric blue intermediate (550), with a long-wavelength absorption at 550 nm, is formed. Heating the glass containing (550) led to benzophenone and S- and O-phenyl thiobenzoate in 85, 14, and 1% yields, respectively (g.l.c.). Compound (390) is identified as 3,3-diphenyloxathiiran. Structures for the intermediate (550) are suggested.