Visible-light promoted serendipitous synthesis of 3,5-diaryl-1,2,4-thiadiazoles via oxidative dimerization of thiobenzamides

In the present manuscript, we report serendipitous synthesis of 3,5-diaryl-1,2,4-thiadiazoles with the aid of a household compact fluorescent lamp (CFL). In presence of alpha-bromo-beta-diketone, thiobenzamides undergo oxidative dimerization to generate corresponding 3,5-diaryl-1,2,4-thiadiazoles in excellent yields in just 5 min instead of expected 2-aryl-4-methyl-5-acylthiazoles. Inhibition of the reaction by free radical scavenger (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) indicates that the dimerization takes place through a free radical process. The synthetic value of the developed protocol was established by synthesizing over eleven diverse 1,2,4-thiadiazoles in a shorter duration with exceptionally high purity and simple work-up procedure under environment benign additive-free conditions. [GRAPHICS] .