Iridium-catalyzed <i>Z</i>-retentive asymmetric allylic substitution reactions.

Abstract

<i>Z</i>-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 <i>E</i>-linear olefins. However, analogous reactions for the synthesis of optically active <i>Z</i>-olefin products are rare. Here we report iridium-catalyzed asymmetric allylic substitution reactions that retain <i>Z</i>-olefin geometries while establishing an adjacent quaternary stereocenter. The formation of transient <i>anti</i>-π-allyl-iridium intermediates and their capture by external nucleophiles before isomerization to the thermodynamically more stable <i>syn</i>-π-allyl-iridium counterparts have been observed. These results provide a promising method for preparing chiral <i>Z</i>-olefinic compounds.