N-Heterocyclic Carbene(NHC)-Catalyzed[3+2]Cycloaddition to Highly Diastereoselective Synthesis of Spirooxindole Dihydrofuran Fused Pyrazolone Compounds
An efficient N-heterocyclic carbene(NHC)-catalyzed[3+2]cycloaddition of isatin-derived enal and pyrazole-4,5-diones to directly synthesis of spirooxindole dihydrofuran fused pyrazolone compounds containing two vicinal spirocenters was disclosed.This approach was qualified with broad substrate scope,achieving moderate to excellent yield(41％～99％)and general to excellent diastereoselective(2∶1～＞20∶1 dr).Furthermore,the reaction has the advantages of mild reaction conditions and easy operation,and the gram scale reaction can also proceed smoothly.This study provides a new synthetic methodology for the efficient construction of multi-functionalized spirooxindole dihydrofuran fused pyrazolone compounds.
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