A Cationic Rhodium-Chiral Diene Complex as a High-Performance Catalyst for the Intramolecular Asymmetric [4+2] Cycloaddition of Alkyne-1,3-Dienes

摘要

The successful development of a transition-metal-catalyzed asymmetric transformation requires the achievement of both high catalytic activity and high enantioselectivity. It is therefore desirable to properly evaluate the relationship between the catalyst activity and the nature of a ligand on the transition metal in a given catalytic reaction, and develop its asymmetric variant by employing a chiral ligand with the required properties for high activity. In this context, we demonstrate herein that a rhodium-diene complex is much more active than its rhodium-bisphosphine counterpart as a catalyst for intramolecular [4+2] cycloadditions of alkyne-tethered 1,3-dienes, and that the use of a chiral diene ligand leads to the development of a highly active and enantioselective asymmetric variant of this reaction.