期刊
ORGANIC & BIOMOLECULAR CHEMISTRY
卷 15, 期 9, 页码 2013-2019出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c7ob00148g
关键词
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资金
- CSIR-New Delhi [ORIGIN-CSC0108]
- NMR
The N-heterocyclic carbene (NHC)-catalyzed enantioselective formal [3 + 2] annulation of alpha,beta-unsaturated aldehydes with 3-hydroxy oxindoles is presented. Under oxidative conditions using the bisquinone oxidant, the reaction resulted in the synthesis of spiro gamma-butyrolactones in moderate to good yields, enantioselectivity and diastereoselectivity. The reaction likely proceeds via the generation of the NHC-bound alpha,beta-unsaturated acylazolium intermediate from enals, which was intercepted by the dioxindoles in a formal [ 3 + 2] pathway to form the spirocyclic compounds. However, a deeper mechanistic investigation revealed that the reaction can also proceed via the homoenolate intermediate. In this case, the dioxindole was oxidized to the corresponding isatin derivative using traces of air under basic conditions, and was intercepted with the NHC-bound homoenolate intermediate in a formal [ 3 + 2] pathway to afford the spiro compound.
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