Carbonyl addition reactions promoted by cerium reagents

Abstract

Organocerium reagents are generated by the reaction of organolithiums with anhydrous cerium chloride or cerium io-dide. The reagents are less basic than organolithiums or Grignard reagents, and they react with various carbonyl compounds to give the corresponding addition products in high yields, even though the substrates are susceptible to enolization or metal-halogen exchange with simple organolithiums. The same reagents react withα,β-unsaturated carbonyl compounds to yield 1,2-addition products with high regioselectivity. It has also been found that cerium chloride significantly promotes the addition reactions of Grignard reagents to carbonyl compounds with remarkable suppression of abnormal reactions. Various tertiary alcohols, which are difficult to prepare by the conventional Grignard reaction, can be synthesized by this method. Several applications of this methodology to practical organic syntheses are described. © 1990, IUPAC.