Abstract: The transformation of N-substituted N-methoxybenzaldehyde hydrazones into the corresponding 1,2-diazabuta-1.3-dienes under the action of carbon tetrachloride in the presence of copper(I) chloride was studied. It was shown that hydrazones of different nature, containing both donor and acceptor groups in the hydrazine fragment, can be involved in the reaction. Further evidence in favor of a radical mechanism of this transformation was obtained using a 3,5-bis(trifluoromethyl)phenylhydrazine derivative. The structural features of the synthesized products were studied by X-ray diffraction analysis. © 2020, Pleiades Publishing, Ltd.