Aldol Condensations with Metal(II) Complex Catalysts

Aldol condensations of aldehydes with ketones catalyzed by the first-row transition metal(II) complexes have been widely studied. Complexes of Co(II), Ni(II), Cu(II), and Zn(II) acetates with 2,2′-bipyridine were effective catalysts to afford cross-aldol condensation products, α,β,-unsaturated ketones, in high yields without any self-condensation products. The reaction of 2-butanone, unsymmetrical aliphatic ketone, with benzaldehyde took place regioselectively to give base-catalyzed-type products.