Preparation of 4-cyanobenzoyl chlorides from alkali metal 4-carbamoyl-benzoates

A process for the preparation of 4-cyanobenzoyl chlorides of formula I,

• wherein
• R is halogen, C1-C4-alkyl, C1-C4-haloalkyl, C1-C4-alkoxy, or C1-C4-haloalkoxy;
• n is 0, 1, or 2;
• the process comprising reacting an alkali metal 4-carbamoylbenzoate of formula II,
• wherein the variables n and R in the alkali metal benzoate of formula II are as defined above for compounds of formula I, and wherein M+ is an alkali metal cation,
• with a chlorinating agent selected from the group consisting of phosgene, diphosgene, and triphosgene;
• the process further comprising an auxiliary solvent and the presence of a carboxamide catalyst of formula C in substoichiometric amounts, based on the amount of alkali metal benzoate of formula II,
• wherein
• RC1 is hydrogen, methyl, or NRC4RC5;
• wherein RC4 and RC5 independently from each other are selected from the group consisting of hydrogen and C1-C4-alkyl;
• RC2 is C1-C4-alkyl;
• or
• RC1 and RC2 together with the group —NRC3—C(═O)— to which they are bound form a saturated or partially unsaturated 5- or 6-membered heterocycle, wherein the heterocycle optionally includes, beside one nitrogen atom, 1 or 2 heteroatoms independently selected from N, O and S as ring member atoms with the provision that the heterocycle cannot contain 2 contiguous atoms selected from O and S;
• and wherein one or two CH2 groups of the heterocycle may be replaced by one or two groups independently selected from C(═O) and C(═S);
• RC3 is hydrogen or C1-C4-alkyl;
• or
• RC2 and RC3 together with the nitrogen atom to which they are bound form a saturated or partially unsaturated 5- or 6-membered heterocycle, wherein the heterocycle optionally includes, beside one nitrogen atom, 1 or 2 heteroatoms independently selected from N, O and S as ring member atoms with the provision that the heterocycle cannot contain 2 contiguous atoms selected from O and S;
• and wherein one or two CH2 groups of the heterocycle may be replaced by one or two groups independently selected from C(═O) and C(═S).