Allylboration of Carbonyl Compounds

Abstract

Abstract Allylic boron compounds have gained a prominent status in organic synthesis for their ability to add with high stereoselectivity to carbonyl compounds such as aldehydes, making them a methodology of choice for the preparation of acetate and propionate units found in several classes of natural products. This remarkable reaction process was discovered in 1964, only to become popular in the 1980s. Using either the dialkylborane or boronate reagents, both the thermal uncatalyzed reaction and the more recent acid‐catalyzed procedures can provide homoallylic alcohol products in high enantioselectivity. The wide of range of possibilities for substitution on the reagent's allylic unit has led to the development of numerous reagents, and the residual alkene unit in the products confers to allylboration chemistry a unique versatility. This chapter presents an exhaustive survey of the useful reagents and their associated carbonyl substrates employed in organic synthesis. The mechanisms and parameters of the reaction are discussed, along with an overview of the different preparative methods for allylic boron reagents. The scope and limitations of these reagents in enantioselective additions, doubly diastereoselective additions, tandem reactions, and other variants is emphasized in the context of applications in natural product synthesis. The literature is covered through early 2006.