Dinuclear Titanium(III)-Catalyzed Radical-Type Kinetic Resolution of Epoxides for the Enantioselective Synthesis of <i>cis</i>-Glycidic Esters
Longfei Li, Shuo Yang, Zhongyun Xu, Shengxiao Li, Jie Jiang, Yongqiang Zhang
Abstract
Glycidic esters represent pivotal constituents in synthetic chemistry, offering enhanced versatility for tailoring toward a diverse array of molecular targets in comparison with simple epoxides. While considerable progress has been made in the asymmetric synthesis of trans - and trisubstituted glycidic esters, achieving enantioselective preparation of cis -glycidic esters has remained a long-standing challenge. Here, we demonstrate a selectivity-predictable modular platform for the asymmetric synthesis of cis -glycidic esters via a novel dinuclear (salen)titanium(III)-catalyzed radical-type kinetic resolution (KR) approach. This radical KR protocol operates under mild conditions and demonstrates a wide substrate scope, facilitating the synthesis of alkyl- and aryl-substituted cis -glycidic esters with high levels of regioselectivity and enantioselectivity, along with hydroxy ester byproducts representing synthetically valuable motifs as well. This study presents a unique exploration of radical-type KR applied to epoxides, effectively overcoming the steric challenges inherent in conventional nucleophilic-type methodologies typically employed in epoxide chemistry.