N‐Bromosulfonamides catalyzed synthesis of new spiro [indoline‐3,4'‐pyrano[2,3‐c]pyrazole] derivatives

An efficient approach for the synthesis of pharmacologically important spiro[indoline‐3,4'‐pyrano[2,3‐c]pyrazole] derivatives from tandem, four component reaction of various hydrazines, isatins, β‐ketoesters, and malononitrile or methyl(ethyl)cyanoester in the presence of N,N,N',N'‐tetrabromobenzene‐1,3‐disulfonamide [ TBBDA ] and poly(N,N'‐dibromo‐N‐ethyl‐benzene‐1,3‐disulfonamide) [ PBBS ] as efficient organocatalysts was reported.