Nickel-catalyzed Reactions between Enone and Two Ethylenes

In the presence of a catalytic amount of Ni(cod)(2) and PCy3, the reaction of (E)-1-phenylbut-2-en-l-one (1a) with ethylene occurred to give three-component addition products, 1,6-enone 2a and 1,5-diketone 4a. The reaction of an enone with two ethylenes gave 2a. The reaction of two enones with an ethylene gave 4a. On the other hand, 2-methyl-1-phenylprop-2-en-1-one (1b) reacted with two ethylenes selectively to give a mixture of 2b and 3b. The reaction might proceed via oxidative cyclization of an enone and an ethylene with nickel(0).