Photochemical reactions of some aromatic thiones with bis(<i>tert</i>‐butylthio)ethyne. Isolation and properties of thietes, the photochemical (2 + 2)‐cycloadducts and their isomeric α,β‐unsaturated dithioesters

Abstract

Abstract Photochemical reaction of some aromatic thiones 2 with bis( tert ‐butylthio)ethyne 1 affords the α,β‐unsaturated dithio esters 4 via a (2 + 2)‐cycloaddition reaction of the triplet‐excited thiones 2 with acetylene 1 . In one case, a (2 + 2)‐cycloadduct, thiete 3 o , was isolated. Spectroscopic investigations revealed that in solution there is an equilibrium between this thiete 3 o and the isomeric α,β‐unsaturated dithio ester 4 o . The generality of this equilibrium phenomenom is examined and discussed with respect to the substituents of the C=C‐C=S moiety of the α,β‐unsaturated dithio esters 4 .