A new approach to the synthesis of N-acyl-l, 2-dihydropyridines based on the cyclization of N-acyl-1-azatrienes is introduced. These latter compounds were not isolated but were produced in the gas phase as transient intermediate by the flash vacuum pyrolysis of 0- methoxycarbonyl N-penta-1, 3-dien-&yl hydroxamic acid derivatives 8.
