A Nickel Catalyst for the Addition of Organoboronate Esters to Ketones and Aldehydes

A Ni(cod)(2)/IPr catalyst promotes the intermolecular 1,2-addition of arylboronate esters to unactivated aldehydes and ketones. Diaryl, alkyl aryl, and dialkyl ketones show good reactivity under mild reaction conditions (<= 80 degrees C, nonpolar solvents, no strong base or acid additives). A dramatic ligand effect favors either carbonyl addition (IPr) or C-OR cross-coupling (PCy3) with aryl ether substrates. A Ni(O)/Ni(II) catalytic cycle initiated by the oxidative cyclization of the carbonyl substrate is proposed.