Photochemical and thermal reactions of heterocycles. Part 3. Photoisomerisation, photofragmentation, and photodimerisation of mesoionic 1,3-dithiol-4-one and -4-imine derivatives

Abstract

Photolysis of the mesoionic 2,5-diphenyl-1,3-dithiol-4-one (7) gave tetraphenyl-1,4-dithiin, tetraphenylthiophen, diphenylacetylene, and sulphur via the corresponding dimer (11) and 4,5-diphenyl-1,2-dithiol-3-one (12) which were isolable under appropriate conditions. Photolysis of the mesoionic N-benzoyl-2-phenyl-1,3-dithiol-4-imines (14) afforded the corresponding 1,2-dithiol-3-imines (15). The photochemical paths of the mesoionic dithiole systems are discussed in the light of the experimental results.