A Highly Enantioselective Homoenolate Michael Addition/Esterification Sequence of Cyclohexadienone-Tethered Enals via NHC Catalysis

Org Lett. 2023 Feb 3;25(4):630-635. doi: 10.1021/acs.orglett.2c04183. Epub 2023 Jan 20.

Abstract

Reported here is a highly enantioselective homoenolate Michael addition/esterification sequence of cyclohexadienone-tethered enals via N-heterocyclic carbene (NHC) catalysis, affording the enantiopure cis-hydrobenzofurans, cis-hydroindoles, and cis-hydroindenes. The NHC catalyst bearing a nitro group greatly enhances the stereocontrol, and a bulky N-aryl substituent of the triazolium salt in the catalyst is helpful for inhibiting the further aldol condensation after homoenolate Michael addition. The utility of this protocol is highlighted by a gram-scale experiment and versatile downstream transformations.