Dinuclear Zinc Catalyzed Enantioselective Dearomatization [3+2] Annulation of 2-Nitrobenzofurans and 2-Nitrobenzothiophenes |
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Authors: | Peng Zhou Yang Yi Dr Yuan-Zhao Hua Dr Shi-Kun Jia Prof Dr Min-Can Wang |
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Institution: | College of Chemistry and Institute of Green Catalysis, Zhengzhou University, No. 100, Science Road, Zhengzhou City, Henan province 450000 P. R. China |
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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 CF3-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. |
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Keywords: | asymmetric catalysis dearomatization reaction dinuclear zinc catalyst 2-nitrobenzofurans 2-nitrobenzothiophenes |
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