De Novo Synthesis of α-Hydroxy Ketones by Gallic Acid-Promoted Aerobic Coupling of Terminal Alkynes with Diazonium Salts.

An unprecedented metal-free direct preparation of unprotected α-hydroxy ketones from terminal alkynes under mild conditions with diazonium salts as the arene source and without the requirement of irradiation is described. The process is general and fully compatible with a wide variety of substitution in both reactants. Experimental and computational evidence strongly suggest the involvement of radical species in the transformation.