Benzeneseleninic acid was used under visible light irradiation (white LEDs) to promote the oxidative cyclization of N-propargyl amides to the respective 2-substituted oxazole-5-carbaldehydes. A total of twelve 2-aryl oxazole-5-carbaldehydes, six of them so far unprecedented, were prepared in 30-90 % yield in just 1 hour of reaction at room temperature. No metal catalysts, nor strong oxidants or heating were necessary, making this a mild method to access a valuable class of compounds. The only coproducts are water and diphenyl diselenide, that can be recovered and converted to new benzeneseleninic acid for a new reaction.

A general methodology to access valuable 4-(phenylchalcogenyl)tetrazolo[1,5-a]quinolines was developed by the reaction of 2-azidobenzaldehyde with phenylchalcogenylacetonitriles (sulfur and selenium) in the presence of potassium carbonate (20 mol%) as a catalyst. The reactions were conducted using a mixture of dimethylsulfoxide and water (7:3) as solvent at 80 °C for 4 h. This new methodology presents a good functional group tolerance to electron-deficient and electron-rich substituents, affording a total of twelve different 4-(phenylchalcogenyl)tetrazolo[1,5-a]quinolines selectively in moderate to excellent yields. The structure of the synthesized 4-(phenylselanyl)tetrazolo[1,5-a]quinoline was confirmed by X-ray analysis.