Enantioselective NHC-catalyzed redox formal [3+2] cycloaddition using α-aroyloxyaldehydes and oxaziridines

An enantioselective N-heterocyclic carbene (NHC)-catalysed formal [3+2] cycloaddition has been developed for the synthesis of oxazolindin-4-one products. The reaction of oxaziridines and α-aroyloxyaldehydes under NHC-redox catalysis provides the formal cycloaddition products with excellent control of diastereo- and enantioselectivity (12 examples, up to >95:5 dr, >99:1 er). A matched-mismatched effect between the enantiomer of the catalyst and oxaziridine was identified, and preliminary mechanistic studies have allowed the proposal of model to explain these observations.

本研究开发了一种对映选择性氮杂环卡宾（N-heterocyclic carbene, NHC）催化的形式[3+2]环加成反应，用于合成恶唑烷-4-酮（oxazolindin-4-one）产物。氧氮丙啶与α-芳酰氧基醛在氮杂环卡宾氧化还原催化下发生反应，可得到该形式环加成产物，且能出色地调控非对映选择性与对映选择性（共12个实例，最高可达>95:5的非对映选择性比例（dr）、>99:1的对映选择性比例（er））。研究人员鉴定出催化剂对映体与氧氮丙啶之间存在匹配-不匹配效应，并通过初步机理研究提出了可解释上述实验现象的反应模型。