A pseudopericyclic [3,5]-sigmatropic rearrangement of a coumarin trichloroacetimidate derivative

Abstract

Thermolysis of a coumarin trichloroacetimidate yields a single rearrangement product. The proposed mechanism is a pseudopericyclic allowed (Woodward–Hoffman forbidden) [3,5]-sigmatropic rearrangement to form the corresponding amide followed by a sigmatropic [1,5]-hydrogen migration. Transition state calculations at the B3LYP/6-31G(d,p) level support this mechanism and suggest the selectivity is influenced by the stability of the intermediates.