A mild and environmentally acceptable synthetic protocol for chemoselective α-bromination of β-keto esters and 1,3-diketones

A wide variety of unsubstituted β-keto esters can be brominated chemoselectively to the corresponding α-monobromo-β-keto esters by using a combination of vanadium pentoxide, hydrogen peroxide and ammonium bromide in a biphasic system, dichloromethane–water at 0–5 °C. In addition, α-mono substituted β-keto esters, cyclic β-keto-esters and 1,3-diketones can also be brominated selectively using the same protocol.