Ketone enamines as dipolarophiles towards C-azidohydrazones

Abstract

The reaction of methyl azido(phenylhydrazono)acetate (1) with the enamines (4)–(7) leads to different kinds of ring-closed products, namely 1,2,4-triazines (8)–(10), 1,2,3-triazoles (12)–(15), and 1,2,4-triazoles (16)–(19). An open-chain azo compound (20) is also formed. In one case, an intermediate 4,5-dihydro-1 H-1,2,3-triazole (11) has been isolated. A mechanistic picture is proposed involving preliminary cycloaddition of the azido group to the enamine and subsequent reaction of the 4,5-dihydro-1 H-1,2,3-triazoles according to various concurrent pathways.