STUDIES ON ENETHIOLS .3. SYNTHESES AND SPECTROSCOPIC INVESTIGATIONS OF BETA-THIOKETOTHIOLESTERS

β-Thioketothiolesters have been prepared by the acid catalysed reaction between β-ketothiolesters and hydrogen sulphide. NMR, IR, and UV spectroscopic investigations show that the title compounds exist mainly as intramolecularly hydrogen-bonded α,β-unsaturated β-mercaptothiolesters both in the pure liquid state and in solution. The thermochromism exhibited by the β-thioketothiolesters has been studied by NMR and is attributed to a shift in the thioketo-enethiol equilibrium. The effect of different solvents on the chelated enethiol system is described and discussed. © 1968.