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Asymmetric Synthesis of Spiro-oxindole-ε-lactones through N‑Heterocyclic Carbene Catalysis

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journal contribution
posted on 07.06.2018, 16:33 by Qiang Liu, Sun Li, Xiang-Yu Chen, Kari Rissanen, Dieter Enders
An unprecedented N-heterocyclic carbene-catalyzed annulation of isatin-derived enals and o-hydroxyphenyl-substituted p-quinone methides as bifunctional reagents has been discovered. The new protocol involves a 1,6-addition of the homoenolate equivalent intermediates to the hydroxy donor–1,6-Michael acceptors and leads to spirocyclic oxindole-ε-lactones in high yields and very good stereoselectivities.