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Report | Regular issue | Vol 20, No. 6, 1983, pp.1035-1042
Published online, 1st January, 1970
DOI: 10.3987/R-1983-06-1035
The Differentital Reactivity of 5- and 3-Methyl Groups in the Reaction of 4-Substituted 2,3,5-Trimethylisoxazolium Salts with Aromatic Aldehydes

Angel Alberola, Ana M. González Nogal, and Francisco J. Pulido

*Deparamento de Química Orgánica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain

Abstract

2,3,5-Trimethylisoxazolium salts with electron-withdrawing groups at C-4 react with aromatic aldehydes to give 3- and/ or 5-arylidene derivatives resulting from the condensation at CH3 and/or CH3-5. The differential reactivity of 3- and 5-methyl groups is markedly influenced by the nature of the substituent at C-4 and varies in the same order as its kinetic acidity which was estimated from studies on deuteriodeprotonation. The influence of inductive, resonance and steric effects due to the 4-substituents on the course of the reaction is shown.