Open chain nitrogen compounds. Part X. Thermolysis of α-diazoacetanilides in methanol: a convenient synthesis of α-methoxyacetanilides from ethyl N-(arylazo)glycinate

Abstract

α-Diazoacetanilides (4), which are readily available from the open-chain triazenes (2), undergo thermolysis in methanol solution to afford the α-methoxyacetanilides (5), an apparently rare type of ether/amide derivative. The methanolic thermolysis is inhibited by the presence of a tertiary amine in the solvent, suggesting that a carbocation, rather than a carbene, intermediate is involved in the conversion of the diazo-amide to the methyl ether. This hypothesis is supported by the retardation of the reaction in the presence of an electron-withdrawing group in the para position of the anilide. The conversion 4 → 5 was also observed, on a small scale, under photolytic conditions. It is suggested that the α-diazoacetanilide represents a useful synthetic equivalent for the synthon ArNHCOCH2+.