A process for the preparation of chlorocarboxylic chlorides of formula (I) in which R<1> and R<2> independently denote a hydrogen atom, a carbon-containing organic radical, a halogen, or a nitro or cyano group; and Y denotes an alkylene chain which contains from 1 to 10 carbons in the chain and which is unsubstituted or substituted by carbon-containing organic radicals, halogen, nitro and/or cyano groups, and the alkylene chain can be interrupted by an ether, thioether, tertiary amino or keto group, and the carbon-containing organic radicals of Y and/or R<1> and/or R<2> can be bonded to each other so as to form a non-aromatic system, by reaction of a lactone of formula (II) in which R<1>, R<2> and Y have the meanings stated above, with a chlorinating agent in the presence of a chlorinating catalyst, in which the reaction is carried out in the presence of a boron compound. |