1-3-Dipolar cycloaddition reactions of diazoalkanes. Part III. Substituent effects on the kinetics of reactions between diazomethane and some unsaturated esters

Abstract

The kinetics of reactions between diazomethane and several conjugated unsaturated esters have been investigated. Reaction rates are governed by steric effects in a manner very similar to that found by Huisgen for corresponding reactions of diphenyldiazomethane. For the series of esters CH₂:CH·CO·OEt, CH₂:C(CH₃)·CO·OEt, CH₃·CH:CH·CO₂Et, the relative rate coefficients for reaction with diazomethane in tetrahydrofuran fall in the sequence 100 : 6·1 : 0·8, respectively. These observations strongly support a concerted cycloaddition process for the reaction mechanism.