Double-Stereodifferentiating Crotylation Reactions with Chiral (E)-CrotyIsilanes. Evaluation of a New Approach for the Synthesis of Polypropionatc-Derivcd Natural Products

摘要

Lewis acid-promoted allylation and crotylation reactions of chiral a-substituted aldehydes have been extensively studied and continue to be an active area of research. By way of analogy, chiral allyl rnetal reagents may be thought of as propionate- and acetate-enolate equivalents for diastereo- and enantioselcctive construction of stereochemically well-defined homoallylic alcohols. Because these reactions complement the aldol reactions, they are among the most important groups of organometallic reagents available for the control of acyclic stereochemistry. It is perhaps interesting to note that, in contrast to the aldol reaction, there is no known biological model for crotylation.