Synthesis and cycloaddition reactions of α-substituted acrolein dimethylhydrazones containing an acetal group

A series of new α-substituted acrolein dimethylhydrazones containing an acetal group were synthesized. These hydrazones react with acrylonitrile or methyl acrylate according to the Diels—Alder reaction pattern to give substituted tetrahydropyridines. An unusual [2+4]- and [2+3]-cycloaddition cascade reaction involving α-diethoxymethylacrolein dimethylhydrazone was discovered.