Iridium-catalyzed Z-retentive asymmetric allylic substitution reactions.

Abstract

Z-Olefins are challenging synthetic targets owing to their relative thermodynamic instability. Transition metal-catalyzed asymmetric allylic substitution reactions are well known for installing stereocenters adjacent to branched or E-linear olefins. However, analogous reactions for the synthesis of optically active Z-olefin products are rare. Here we report iridium-catalyzed asymmetric allylic substitution reactions that retain Z-olefin geometries while establishing an adjacent quaternary stereocenter. The formation of transient anti-π-allyl-iridium intermediates and their capture by external nucleophiles before isomerization to the thermodynamically more stable syn-π-allyl-iridium counterparts have been observed. These results provide a promising method for preparing chiral Z-olefinic compounds.