Concerning the Mechanism of the Asymmetric Diels‐Alder Reaction: First Crystal Structure Analysis of a Lewis Acid Complex of a Chiral Dienophile

Abstract

A seven-membered ring chelate structure, hitherto unknown in the case of titanium compounds, characterizes the complex 1. Presumably, this complex is the reactive species in solution in the TlCl4-catalyzed Diels-Alder reaction of allyl lactates with dienes. An X-ray structure analysis of the complex shows that the Re-side of the CC double bond is well shielded by one of the chlorine atoms.