Mechanism of Dehydroacetoxylation from Methyl 3-Acetoxy-3-aryl-2-halogeno-arylpropanoates

CABALEIRO, M. C.; GARAY, R. O.

JOURNAL OF THE CHEMICAL SOCIETY. PERKIN TRANSACTIONS 2 (2001)

RSC

Lugar: Londres; Año: 1986 p. 1091 - 1095

1472-779X

The rate of sodium methoxide-induced dehydroacetoxylation of the diesters p-RC6H4CH(OAc)CXHCO2Me (X = Br or Cl) has been studied as a function of the para-substituent. The results correspond to the para-substituent effects expected for proton abstraction from C-2, as estimated from the diastereoisomerisation of model compounds [p-RC6H4CH(OMe)CXHCO2Me] under similar conditions. This suggests that the elimination occurs via a carbanion mechanism, with C(2)?H bond-breaking rate-determining. The apparent insensitivity of the kinetic behaviour to configuration differences, together with the response of the reactions to the effect of the 3-substituent, is interpreted in terms of inductive stabilisation by the 2-halogen atom, which tends to localise the incipient negative charge at C-2, inhibiting distortion of its tetrahedral geometry.