A novel and efficient method for the one-pot transformation of β-hydroxycarbonyl compounds to a-brominated 1,3-dicarbonyl compounds is achieved with MoO2Cl2 in the presence of N-bromosuccinimide. All the reactions were carried out under mild conditions and provide good yields of the products. No bromination occurs at benzylic and allylic positions. © Georg Thieme Verlag Stuttgart · New York.