Construction of Highly Substituted Stereodefined Dienes by Cross‐Coupling of α‐Allenic Acetates

Abstract

AbstractThe assembly of highly substituted dienes remains a challenge for organic chemistry. This work represents a strategyfor the construction of highly substituted 1,3‐dienes by meansof a Tsuji–Trost cross coupling between α‐allenic acetates and organozinc reagents. The reaction is high yielding, and installs a trisubstituted olefin with E/Z selectivities up to 95:5 favoring the (E) product. A cheap, commercially available palladium precatalyst and a ligand are used to control theE/Z selectivity. Furthermore, an interesting reversal in selectivity is noted in which appropriate choice of ligand may be used to control the outcome of the reaction and favor the (Z) product. Thirteen examples are described, highlighting the substrate scope of the reaction. It is hoped that the straightforward reaction conditions and high selectivity will make this reaction of broad use in natural product chemistry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)