ChemInform Abstract: Copper-Catalyzed Aerobic Dehydrogenation of C-C to C=C Bonds in the Synthesis of Pyridazinones

A simple and efficient procedure for the synthesis of pyridazin-3(2H)-ones through copper-catalyzed dehydrogenation of a single C–C bond of 4,5-dihydropyridazin-3(2H)-ones to a C=C bond with oxygen as the terminal oxidant is described. Functional groups including hydroxy, carboxylic, bromo, chloro, cyano, nitro and alkoxy were all tolerated under the reaction conditions. Moreover, this methodology was applied to the preparation of a series of structurally similar N-substituted 6-phenylpyridazinone compounds containing fluorine. The dehydrogenation reactions exhibit good yields and selectivity.