Dual Lewis Acid Promoted/Visible Light Driven Preparation of Aryl Diazenyl Oxazoles from Isocyanoacetamides and Arylazo Sulfones

While arylazo sulfones have been widely applied as arylating agents, their exploitation for diazenylation reactions has been previously limited to electron-rich alkenes such as styrenes and silyl enol ethers. Herein we optimized a synthetic one-pot protocol to access oxazolyl azo compounds via a selective domino ring-closing/aryldiazenylation sequence by starting from arylazo sulfones and isocyanoacetamides in the presence of Sm(OTf)3 as the Lewis acid. The satisfactory substrate scope and functional group tolerance, along with scale-up reaction both in batch and under continuous flow conditions provide a valuable approach to such a class of heteroaryl azo compounds.