Water-controlled selective preparation of α-mono or α, α′-dihalo ketones via catalytic cascade reaction of unactivated alkynes with 1,3-dihalo-5,5-dimethylhydantoin

The control of a reaction that can produce multiple products from the same starting material is a highly attractive and challenging concept in organic synthesis. An efficient protocol for the selective synthesis of alpha-mono or alpha, alpha'-dihalo ketones via a water-controlled three-component thiourea-catalyzed cascade reaction of unactivated alkynes, 1,3-dihalo-5,5-dimethylhydantoin and water has been developed. a-Monohaloketones were obtained in aqueous acetone at 45 degrees C; conversely, alpha, alpha'-dihalo ketones were formed with pure water as the sole solvent at room temperature.