Synthesis of 3-Chloro-6-(4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)pyridazine and Its Deuterated Analogue

The synthesis of 3-chloro-6-(4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)pyridazine and its deuterated analogue was performed using a novel two-step sequence. On the first step, a double chlorination of 3-(3,5-dimethyl-1H-pyrazol-1-yl)-6-hydrazinyl-1,2,4,5-tetrazine with trichloroisocyanuric acid was performed to synthesize 3-chloro-6-(4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazine for the first time. The latter reacted with calcium carbide-derived acetylene and D₂-acetylene at heating in a two-chamber reactor (COware) producing 3-chloro-6-(4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)pyridazine or 3-chloro-6-(4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)-4,5-dideuteropyridazine respectively in quantitative yields.