N -heterocyclic carbene-mediated formal [3+3] annulation of isatin-derived α, β-unsaturated acids: Access to functionalized 3,4′-spirooxindole δ -lactones
作者:Weiguo Zhang、Junyu Xu、Jing Cao、Chao Fang、Jindong Zhu、Tao Lu、Ding Du
DOI:10.1016/j.tet.2017.04.055
日期:2017.6
acids 2 for the generation of isatin-derived α,β-unsaturated acyl azoliums II was described. The acyl azoliums II were successfully applied to undergo a formal [3 + 3] annulation with 1,3-dicarbonyl compounds to access functionalized 3,4′-spirooxindole δ-lactones 4. A scale-up synthesis and an enantioselective variant of this protocol were also investigated. The stable and easily prepared acids 2 may