A planar chiral organoselenium enabled enantioselective intramolecular oxidation of trisubstituted olefins.

Abstract

Electrophilic selenium catalysis has recently emerged as an attractive synthetic strategy, yet the field of enantioselective electrophilic selenium catalysis remains underdeveloped, primarily due to the scarcity of efficient chiral catalysts and limited reaction types. Herein, we disclose the design and synthesis of a series of planar chiral organoseleniums based on [2.2]paracyclophane. With these chiral organoseleniums as catalysts, we accomplish a highly enantioselective intramolecular oxidative etherification of trisubstituted olefins, providing a diverse array of optically pure chromans bearing a quaternary carbon stereocenter. The stereochemical versatility of this method enables efficient access to both product enantiomers from the same catalyst by adjusting the E/Z configurations of the olefins. Importantly, comprehensive control experiments and kinetic studies elucidate the reaction mechanism, identifying the oxidation of selenenylated cyclic ether as the likely turnover-limiting step. DFT calculations demonstrate that both steric hindrance and weak interactions play a vital role in enantioselectivity.