Green synthesis of novel spiro[indoline-3,4'-pyrazolo[3,4-b]pyridine]-2,3'(7'H)- dione, spiro[indeno[1,2-b]pyrazolo[4,3-e]pyridine-4,3'-indoline]-2',3-dione, and spiro[benzo [h]pyrazolo[3,4-b]quinoline-7,3'-indoline]-2',8(5H)-dione derivatives in aqueous medium

Abstract The green synthesis of novel spiro[indoline-3,4′-pyrazolo[3,4- b ]pyridine]- 2,3′(7′ H )-dione, spiro[indeno[1,2- b ]pyrazolo[4,3- e ]pyridine-4,3′-indoline]-2′,3-dione, and spiro[benzo[ h ]pyrazolo[3,4- b ]quinoline-7,3′-indoline]-2′,8(5 H )-dione derivatives was reported. The reactions were carried out smoothly in water in the presence of acetic acid with high yields. Some products could be obtained by direct filtration from the water without further purification. The advantages of this approach were simple operation, mild reaction conditions, easy isolation, and wide scope substrates. Most important of all, this reaction process is green.