A Highly Enantioselective Homoenolate Michael Addition/Esterification Sequence of Cyclohexadienone-Tethered Enals via
Ya-Jie Wang1, Yi-Fan Wang1, Wen-Yu Kang1
1The Research Center of Chiral Drugs, Shanghai Frontiers Science Center for TCM Chemical Biology, Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Road, Shanghai 201203, China.
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.
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