Catalyst-Free Synthesis of Xanthene and Pyrimidine-Fused Heterocyclic Derivatives at Water-Ethanol Medium and Their Antioxidant Properties

Water-ethanol (1:1 v/v) reaction medium has been demonstrated to be an efficient system for the catalyst-free synthesis of biologically potent xanthene and pyrimidine-fused heterocyclic derivatives at 60 degrees C. Reactions of various substituted benzaldehydes or salicylaldehydes with dimedone or barbituric acid in water-ethanol yield corresponding xanthene and pyrimidine-fused heterocyclic derivatives, respectively, in good yields (90-93%) within a short time frame (1-2 h). This synthetic protocol is eco-friendly and economically viable and has a facile workup procedure and a wide scope. The synthesized compounds were screened for their antioxidant activities against 2,2-diphenyl-1-picryl hydrazyl (DPPH) and ferric-reducing antioxidant power (FRAP) assays. Compounds 13 and 23 are excellent free radical scavengers toward DPPH free radicals and compounds 12 and 23 show good activities in FRAP assay compared with standard Vitamin C.