Novel oxidation system of benzoins to benzils for synthesis and antioxidant activity studies of (5-oxo-4,4-diarylimidazolidin-2-ylidene)cyanamides

In this work, the two novel methods were achieved for the preparation of benzil derivatives 2a–f with high yields and short reaction time from benzoins 1a–f via; (i) their refluxing with a mixture of sulfur and morpholine in ethanol, and (ii) their stirring with oxidizing agent "DMSO-NaBr-H2SO4 system" at 85 °C. Thus, a new series of (5-oxo-4,4-diarylimidazolidin-2-ylidene)cyanamide 3a–f was already synthesized from the reaction of benzils 2a–f with commercially available cyanoguanidine in the presence of sodium ethoxide as a basic catalyst. The new products 3a–f were exhibited promising antioxidant activity based on "in vitro" assays in 2,2-diphenyl-1-picrylhydrazyl (DPPH) compared to vitamin C.