Synthesis of pyranocoumarin fused spirooxindoles via Knoevenagel/Michael/cyclization sequence: a regioselective organocatalyzed multicomponent reaction

Synthesis of pyranocoumarin fused spirooxindole derivatives from the three-component reaction of isatin, malononitrile, and 5,7-dihydroxy-4-methyl-2H-chromen-2-one using piperidine as organocatalyst has been reported. Replacing malononitrile by ethyl cyanoacetate and using methanol as solvent, the same protocol provides the corresponding transesterified products. The salient features of this protocol are metal-free reaction conditions, easy isolation of products, applicability to a wide range of isatins with good yields and formation of only one regioisomer among the three possible products.

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