Equilibria between enamine and α,β-unsaturated imine in cephalosporin hydrolysis

The normal product of hydrolysis of cephalosporins with a leaving group at C-3′ is an α,β-unsaturated imine which is demonstrated to be in equilibrium with its precursor, an enamine; the equilibrium constants for this process are reported for thiolate anions which generate a Bronsted βlg of 0.71.