Chiral catalysts for enantioselective carbenoid cyclopropanation reactions

Abstract

AbstractChiral copper(I) and rhodium(II) catalysts designed to achieve enantioselection in cyclopropanation reactions have recently been reported. These catalysts react with diazo compounds to form intermediate metal carbenes that subsequently react with alkenes, in both intermolecular and intramolecular transformations, to form cyclopropane derivatives. They are constructed with chiral ligands whose function is to orient carbene substituents and control olefin approach to the carbenoid center. Enantioselectivities that are greater than 95% have been achieved.In this review, the major advances in chiral catalyst design and development are described, and a uniform mechanistic interpretation is advanced to explain the results accumulated in reported investigations. Focus is placed on chiral salicylaldimine and semicorrin/bis‐oxazoline copper catalysts and on the newest class of chiral catalysts for enantioselective carbenoid reactions, rhodium(II) carboxamides. Although early in their development, sufficient advances have been made to justify placement of this catalytic methodology among the most promising for enantioselective cyclopropanation reactions.