Oxybromination of Ethynylbenzene Catalysed by Molybdenum Complexes in Organic Solvent and in Ionic Liquids

The molybdenum(VI)-catalysed oxybromination of ethynylbenzene was performed with hydrogen peroxide as oxidant and potassium bromide as source of bromine, in a two-phase water/solvent system, where solvent was either dichloromethane or an ionic liquid. The selectivity was toward 1,2-dibromostyrene when performed in water/dichloromethane. In ionic liquids better yields and shorter reaction times were obtained that, together with the complete ethynylbenzene conversion and the preferred formation of α,α-dibromoacetophenone, make the reaction synthetically useful.