Dinuclear Zinc Catalyzed Enantioselective Dearomatization [3+2] Annulation of 2‐Nitrobenzofurans and 2‐Nitrobenzothiophenes
Peng Zhou, Yang Yi, Yuan‐Zhao Hua, Shi‐Kun Jia, Min‐Can Wang
Abstract
Abstract The application of dinuclear zinc catalysts in a dearomatization reaction has been developed. Catalytic asymmetric dearomatization [3+2] annulations of 2‐nitrobenzofurans or 2‐nitrobenzothiophenes with CF 3 ‐containing N ‐unprotected isatin‐derived azomethine ylides catalyzed by dinuclear zinc catalysts are realized with excellent diastereomer ratios (dr) of >20 : 1 and enantiomeric excess (ee) of up to 99 %. This protocol provides a practical, straightforward access to structurally diverse pyrrolidinyl spirooxindoles containing a 2,3‐fused‐dihydrobenzofuran (or dihydrobenzothiphene) moiety, and four contiguous stereocenters. Reactions can be performed on a gram scale. The absolute configuration of products is confirmed by X‐ray single crystal structure analysis, and a possible mechanism is proposed.