Solutia and JLM Industries end benzene-to-phenol agreement

Abstract

Treatment of α-imino esters derived from glycine esters and benzophenone or benzaldehydes with potassium tert butoxide in DMSO gave persistent solutions of carbanions at 20 °C. The kinetics of their reactions with quinone methides and benzylidene malonates (reference electrophiles) have been followed photometrically under pseudo-first order conditions. The reactions followed second-order rate laws. Since addition of 18-crown-6 ether did not affect the reaction rates, the measured rate constants correspond to the reactions of the non-paired carbanions. Plots of the second-order rate constants against the electrophilicity parameters E of the electrophiles are linear, which allowed us to derive the nucleophile-specific parameters N and sN, according to the linear Gibbs energy relationship lg k2(20 °C) = sN(N + E). The Ph2C = N- and PhCH = N- groups act as very weak electron acceptors with the consequence that Ph2C = N-CH–-CO2R and PhCH = N-CH–-CO2R have a similar nucleophilicity as Ph-CH–-CO2Et, the anion of ethyl phenylacetate.