Access to gem-Dibromoenones Enabled by Carbon-Centered Radical Addition to Terminal Alkynes in Water Solution.

We herein report a novel and more practical approach to prepare gem-dibromoenones from terminal alkynes, tetrabromomethane (CBr4), and water in a single step. Mechanistic studies reveal that the generation of a tribromomethyl radical with the assistance of a persulfate salt (K2S2O8) is essential to this transformation. The reaction features readily available chemicals, a broad substrate scope, a green solvent, and mild reaction conditions, providing an efficient alternative for construction of halogen-substituted enones.