Enantioselective Synthesis of N‐Phenyl‐dihydropyrano[2,3‐c]pyrazoles via Cascade Michael Addition/Thorpe‐Ziegler Type Cyclization Catalyzed by a Chiral Squaramide |
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Authors: | Junhua Li Daming Du |
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Institution: | School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing 100081, China |
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Abstract: | Enantioselective synthesis of biologically active dihydropyrano2,3‐c]pyrazoles has been achieved through a squaramide‐catalysed Michael addition/Thorpe‐Ziegler type cyclization cascade reaction between arylidenepyrazolones and malononitrile. A series of optically active dihydropyano2,3‐c]pyrazoles were obtained in excellent yields (up to 99%) and moderate to good enantioselectivities (up to 79% ee) under mild reaction conditions. |
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Keywords: | organocatalysis squaramide heterocycles Michael addition cyclization |
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