Process for the preparation of compounds of formula (I) wherein R is halogen, R.sub.1O.sub.1R.sub.1S(O).sub.n or (R.sub.1).sub.2NC(X)O; R.sub.1 is C.sub.1-C.sub.8alkly, aryl-C.sub.1-C.sub.8alkyl, C.sub.1-C.sub.8haloalkyl or aryl; n is 0, 1, 2 or 3; X is O or S; and R.sub.2 is hydrogen, C.sub.1-C.sub.4alkyl or C.sub.1-C.sub.4haloalkyl, in which process, in a solvent, (1) an aniline derivative of formula (IV) wherein R is as defined above, and R.sub.3 is C.sub.1-C.sub.5alkyl or C.sub.1-C.sub.5haloalkyl, is diazotised in the presence of a mineral acid to form the corresponding diazonium salt of formul (II) wherein R and R.sub.3 are as defined above, A.sup.m- is an anion, and m is 1 or 2, (2) the resulting diazonium salt of formula (II) is carbonylated in the presence of a catalyst, CO and optionally a buffer, to form a benzoic acid derivative of formula (III) wherein R and R.sub.3 are as defined above, and (3) the benzoic acid derivative of formula (III) is then subjected to benzylic lactonisation in the ortho-position alkyl chain R.sub.3 in the presence of a free-radical initiator and a halogenating agent.
