Low Coordination State Rh<sup>I</sup>‐Complex as High Performance Catalyst for Asymmetric Intramolecular Cyclopropanation: Construction of<i>penta</i>‐Substituted Cyclopropanes
Junyou Zhang, Weici Xu, Ming‐Hua Xu
Abstract
Abstract A simple, broad‐scope rhodium(I)/chiral diene catalytic system for challenging asymmetric intramolecular cyclopropanation of various tri ‐substituted allylic diazoacetates was successfully developed. The low coordination state Rh I ‐complex exhibits an extraordinarily high degree of tolerance to the variation in the extent of substitution of the allyl double bond, thus allowing the efficient construction of a wide range of penta ‐substituted, fused‐ring cyclopropanes bearing three contiguous stereogenic centers, including two quaternary carbon stereocenters, in a highly enantioselective manner with ease at catalyst loading as low as 0.1 mol %. The stereoinduction mode of this Rh I ‐carbene‐directed asymmetric intramolecular cyclopropanation was investigated by DFT calculations, indicating that π‐π stacking interactions between the aromatic rings of chiral diene ligand and diazo substrate play a key role in the control of the reaction enantioselectivity.