Isomerization of enol esters derived from 2-acyl-1,3-cyclohexanediones: mechanism and driving force

A series of 2-acyl-1,3-cyclohexanediones were prepared and isomerization mechanisms of the corresponding enol esters were investigated. The driving force for this migration is likely that the intrinsic electrostatic repulsion between the 2-acyl oxygen atom and the two 1,3-diketone oxygens caused deformation of enol esters from planarity and resulted in their high susceptibility to enolization and subsequent isomerization.