3-Amino-2-mercaptobenzoic acid derivatives and processes for their preparation

A process for the preparation of a compound of the formula I or a salt thereof ##STR28## which comprises reacting a compound of the formula II in which X is halogen,

• n is 0, 1, 2 or 3;
• Z is CN, CO-A or CS-A,
• A is hydrogen, halogen, OR.sub.1, SR.sub.2 and N(R.sub.3)R.sub.4 ;
• R.sub.1 to R.sub.4 are hydrogen, a substituted or unsubstituted, open-chain, saturated or unsaturated hydrocarbon radical containing not more than 8 carbon atoms, a substituted or unsubstituted cyclic, saturated or unsaturated hydrocarbon radical containing not more than 10 carbon atoms, substituted or unsubstituted benzyl or phenethyl, a substituted or unsubstituted alkanoyl group containing not more than 8 carbon atoms, a substituted or unsubstituted benzoyl group or a substituted or unsubstituted heterocyclyl radical;
• or R.sub.3 and R.sub.4, together with the nitrogen atom to which they are bonded, are a 5- or 6-membered, substituted or unsubstituted heterocyclic radical having 1-3 heteroatoms O, S and/or N, and in which p1 T is hydrogen, C.sub.1 -C.sub.6 alkyl, C.sub.3 -C.sub.6 alkenyl, C.sub.3 -C.sub.6 alkynyl, C.sub.3 -C.sub.6 cycloalkyl or substituted or unsubstituted phenyl, benzyl or phenethyl;
• with a strong aqueous base to give a compound of the formula Ia or a salt thereof and further reacting this to give a compound of the formula I in which
• X, n and Z are as defined for formula I.