Photochemical cycloaddition of thiocarbonyl compounds to diphenylketene and a related ketenimine

Abstract

Diphenylketene undergoes photocycloaddition with N-methylthiophthalimide, N-methyldithiophthalimide or xanthene-9-thione, to give a Spiro-adduct containing a thietan-2-one ring. The photoproducts from the thioimide substrates are themselves photolabile, eliminating COS to form an alkene. Diphenyl-N-(p-tolyl)ketenimine gives analogous 2-iminothietanes on irradiation with the thioimides.