Process for halogenating carboxylate compounds having at least one reactive alpha hydrogen substituent, comprising contacting said carboxylate compound with a halogen or halogen source in the presence of an effective amount of a cyanoquinone compound and acidic auxiliary agent, a catalyse system comprising the cyanoquinone material and the acidic auxiliary agent, and a halogenation medium comprising a halogen, selected from chlorine and bromine and a catalyst system comprising a cyanoquinone material and an acidic auxiliary agent.