Asymmetric Synthesis of Spirocyclopentane Oxindoles Containing Four Consecutive Stereocenters and Quaternary α‑Nitro Esters via Organocatalytic Enantioselective Michael–Michael Cascade Reactions

An enantioselective domino Michael–Michael
reaction of nitroolefins
and 2-nitro-3-arylacrylates has been established, which provided a
series of spirocyclopentane oxindoles with four consecutive stereocenters
including quaternary α-nitro esters with good yields (up to
73%) and excellent enantioselectivities (up to 97% ee). The reaction
was realized and optimized with the aid of a chiral squaramide-amine
catalyst. The structures of 11 products were confirmed by single-crystal
X-ray diffraction analysis.

本研究建立了硝基烯烃与2-硝基-3-芳基丙烯酸酯的对映选择性多米诺Michael-Michael反应，该反应可合成一系列含有四个连续立体中心的螺环戊烷氧化吲哚类产物，其中包含季碳α-硝基酯结构，产物收率优良（最高达73%），对映选择性优异（最高达97% ee）。该反应在手性方酰胺-胺催化剂的辅助下得以实现并优化。通过单晶X射线衍射分析确认了11个产物的结构。