Studies on Hydrogenation by Nickel Complexes. 5. The Selective Hydrogenation of 1,4-Cyclohexadienes to Cyclohexenes Catalyzed by a Nickel Complex

Article abstract of DOI:10.1246/bcsj.60.2923

1,4-Cyclohexadiene was hydrogenated selectively to cyclohexene with a nickel catalyst generated from bis(acetylacetonato)nickel(II), triethyldialuminium trichloride, and triphenylphosphine at 40 deg C under an atmospheric pressure of hydrogen.The hydrogenation of eleven kinds of alkyl-substituted 1,4-cyclohexadienes gave the corresponding cyclohexenes in good yields by the nickel catalyst.The structural factors of the alkyl substituent on the diolefin are shown to affect the hydrogenation rate.The homogeneous nickel catalyst system, in which a nickel hydride complex NiH(PPh3)(AlCl4) is supposed to be an active species, was effective for the selective hydrogenation of the diolefin to the olefin.A plausible pathway involving ?-allylnickel complexes for the hydrogenation is proposed.