Catalytic Cross-Coupling of Secondary Alcohols.

Abstract

Herein, an unprecedented ruthenium(II) catalyzed direct cross-coupling of two different secondary alcohols to β-disubstituted ketones is reported. Cyclic, acylic, symmetrical, and unsymmetrical secondary alcohols are selectively coupled with aromatic benzylic secondary alcohols to provide ketone products. A single catalyst oxidizes both secondary alcohols to provide selectively β-disubstituted ketones to broaden the scope of this catalytic protocol. Number of bond activation and bond formation reactions occur in selective sequence via amine-amide metal-ligand cooperation operative in Ru-MACHO catalyst. The product-induced diastereoselectivity was also observed. Kinetic and deuterium labeling experiments suggested that the aliphatic secondary alcohols undergo oxidation reaction faster than benzylic secondary alcohols, selectively assimilating to provide the cross-coupled products. Reactions are sensitive to steric hindrance. This new C-C bond forming methodology requires low catalyst load and catalytic amount of base. Notably, the reaction produces H2 and H2O as the only byproducts making the protocol greener, atom economical and environmentally benign.