Asymmetric synthesis via axially dissymmetric molecules. A binaphthol-modified complex aluminum hydride reagent possessing extremely high ability of chiral recognition

Abstract

A new chiral hydride reagent. BINAL-H has been devised by the modification of lithium aluminum hydride with axially dissymmetric (S)- or (R)-binaphthol and a simple alcohol. This reducing agent possesses exceptionally high enantioface-differentiating ability and reduces a wide variety of structurally diverse unsaturated (but not saturated) carbonyl substrates in high optical yields and in a predictable manner. A six-membered ring transition state model is proposed to explain the stereochemical consequences. The unsaturated moiety and alkyl group attached to the carbonyl function is differentiated primarily by the difference in the electronic properties rather than the bulkiness. The utility of the asymmetric reduction is exemplified by the efficiently stereocontrolled synthesis of prostaglandin intermediates, some insect pheromones, chiral primary terpenic alcohols, etc. © 1981 IUPAC