Photochemical rearrangements of substituted thiochromanone sulfoxides

The photochemical behavior of a number of substituted derivatives of thiochroman-4-one 1-oxide has been examined. In contrast to the analogous sulfones these sulfoxides undergo a variety of photochemical rearrangements. At least three distinct pathways have been recognized; β-hydrogen abstraction or rearrangement to cyclic sulfenates, which then undergo further reaction by homolysis of the SO bond, appearing to be particularly favorable processes. In a small number of examples, photochemical deoxygenation is observed as a competing reaction. Mechanisms which attempt to account for the influence of structural variations on the particular pathway followed have been proposed.