Structural study of methyl and tert-butyl phenylacetate enolates in solution: spectroscopic determination of their E or Z configuration

A study was done on the structures of Li and K methyl and tert-butyl phenylacetate enolates A,M and B,M using Ir and NMR spectroscopy. It was shown that deprotonation of these compounds produced enolates whose E and Z geometry and association were affected by the cation and solvent. Charge delocalization in the phenyl ring and steric hindrance in the tert-butyl ester enolate produced a low aggregation degree among Li(E)-enolates.