A Highly Enantioselective Homoenolate Michael Addition/Esterification Sequence of Cyclohexadienone-Tethered Enals via NHC Catalysis.
Ya-Jie WangYi-Fan WangWen-Yu KangWen-Ya LuYu-Hui WangPing TianPublished in: Organic letters (2023)
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.