Selenium Dioxide-Mediated Bromination of α,β-Unsaturated Ketones Using -Bromosuccinimide in the Presence of -Toluenesulfonic Acid: A Versatile Route for the Synthesis of α'-Bromo-4-arylbut-3-en-2-one and α',α'-Dibromo-4-arylbut-3-en-2-one.

An efficient method for the synthesis of α,β-unsaturated α'-bromoketones and α,β-unsaturated α',α'-dibromoketones is described using -bromosuccinimide (NBS) as the brominating agent mediated by selenium dioxide (SeO) in the presence of -toluenesulfonic acid (PTSA) monohydrate in toluene. The method is simple, employing easily available shelf reagents to afford a wide range of products in good yields. The method highlighted that simple fine-tuning of the reaction conditions and molar equivalents of the reactants easily affords either mono- or dibrominated products in excellent yields. A number of these products have not been reported in the literature. All of the reactions were carried out in gram-scale quantities.