Thermal reversal of the photochemically induced cis–trans-isomerisation of α-(3H-1,2-dithiol-3-ylidene) ketones and aldehydes. Substituent effects

Abstract

Sixteen substituted α-(3H-1,2-dithiol-3-ylidene) ketones and aldehydes have been shown to give trans-isomers and not O-S bonded valence tautomers upon photolysis. The cis–trans-isomerization was found to be a photochemical process whereas the trans–cis-isomerization was a thermal process. The rate constants for the trans–cis-isomerization were found to be controlled mainly by steric factors.