CHEMOSELECTIVE REDUCTION OF ALPHA,BETA-UNSATURATED KETONES CATALYZED BY TRANSITION-METAL COMPLEXES WITH POLYDENTATE LIGANDS

This paper reviews the catalytic activity of various Group 8 and 9 met al complexes stabilized by polydentate ligands in hydrogen-transfer re ductions of alpha,beta-unsaturated ketones. Bi- and tri-dentate ligand s with mixed P,N, -P2N and P2N2 donor atom sets are appropriate for th e synthesis of efficient iridium catalysts capable of selectively redu cing alpha-beta-unsaturated ketones to allylic alcohols. Chemoselectiv e catalysts containing the metals of the iron triad are obtained with the tripodal tetradentate P(CH(2)CH(2)PPh(2))(3). Activity, chemoselec tivity and catalysis mechanisms are compared and contrasted within the various types of complex.