Dual role of the polymer supported catalyst PEG-OSO3H in aqueous reaction medium: synthesis of highly substituted structurally diversified coumarin and uracil fused spirooxindoles

A highly convergent, efficient, and practical heteroannulation protocol for the synthesis of a library of uracil and coumarin fused spirooxindole derivatives has been developed. Reactions involving PEG-OSO3H mediated one-pot three-component domino coupling of 1,3-diketo compound (cyclohexane-1,3-dione, indane-1,3-dione, dimedone, and 1,3-dimethylbarbituric acid), 6-aminouracil/4-aminocoumarin, and isatin/5-bromoisatin resulted in the highly substituted uracil and coumarin fused spirooxindole derivatives, making this strategy very useful in diversity-oriented synthesis (DOS). This synthesis was established to follow the group-assistant-purification chemistry process (GAP) avoiding traditional chromatography, whereupon recrystallization purifications appear to be a very good alternative to the traditional classical methods. The aqueous reaction medium, dual role of the polymer supported catalyst PEG-OSO3H in aqueous media, easy recovery of the catalyst, and high yield make the protocol attractive, sustainable, and economic. (C) 2012 Elsevier Ltd. All rights reserved.