1,3-Dipolar cycloaddition reactions of diazoalkanes. Part I. Kinetics and mechanism of the reactions between diazomethane or diazoethane and methyl acrylate or methyl methacrylate

Abstract

The reactions between diazomethane and methyl acrylate or methyl methacrylate have been studied and found to show features similar to those observed in related reactions involving diazodiphenylmethane. Reaction rates were essentially independent of solvent polarity and for tetrahydrofuran solvent there was a large negative entropy of activation. These observations strongly support a concerted 1,3-dipolar cycloaddition methanism for the formation of pyrazolines from diazoalkanes and conjugated olefins. For the reaction with methyl methacrylate, diazoethane is nine times more reactive than diazomethane.