Regiospecificty in the heterocyclization of β-oxonitriles to 5-substituted 4-oxothiazolidine derivatives

Abstract

Astudy on the regiospecificity of the base-catalyzed reaction of activated ?-oxonitriles 1 with diethyl mercaptosuccinate affording the title compounds 3 is reported. Other competitive heterocyclic products, that is 4-oxo-1,3-thiazinanes 4, derivatives of tetrahydrothiophene 5 and/or thiacyclohexane 6 which on the grounds of mechanistic considerations could be formed, were not observed. Spectroscopic and experimental evidence together with theoretical considerations, provides a reasonable explanation for the observed regiospecificity.