Preparation of 2-chloropyridine derivatives

A process for the preparation of a compound of the formula ##STR3## in which R represents a group --CONR.sup.1 R.sup.7 or --SO.sub.2 R.sup.8 where R.sup.1 and R.sup.7 independently represent a hydrogen or an optionally substituted C.sub.1-10 alkyl or aryl group and R.sup.8 represents an optionally substituted C.sub.1-10 alkyl or aryl group;

• R.sup.2 represents a hydrogen atom or an optionally substituted C.sub.1 -10 alkyl or C.sub.1-10 alkoxy group;
• and
• R.sup.3 and R.sup.4 independently represent a hydrogen atom or an optionally substituted C.sub.1-10 alkyl or C.sub.14 10 alkoxy group or R.sup.3 and R.sup.4 together represent an optionally substituted C.sub.1-8 alkylene group;
• said process comprising the steps of reacting gaseous hydrogen chloride in the presence of a solvent with a compound of the formula ##STR4## in which R, R.sup.2, R.sup.3, and .sup.4 are as defined above and R.sup.5 and R.sup.6 independently represent a hydrogen atom or an optionally substituted C.sub.1-10 alkyl, C.sub.2-10 alkenyl, C.sub.2-10 alkynyl, C.sub.3-10 cycloalkyl or aryl group or R.sup.5 and R.sup.6 together with the interjacent nitrogen atom represent an optionally substituted pyrrolidine ring,
• said optional substituents being selected from halogen atoms, nitro, cyano, hydroxyl, C.sub.3-6 cycloalkyl, C.sub.1-6 alkyl, C.sub.1-6 haloalkyl, C.sub.1-6 alkoxy, C.sub.1-6 haloalkoxy, amino, C.sub.1-6 alkylamino, di-C.sub.1-6 alkylamino, formyl, C.sub.1-6 alkoxycarbonyl, carboxyl, C.sub.1-6 alkanoyl, C.sub.1-6 alkylthio, C.sub.1-6 alkylsulphinyl, C.sub.1-6 alkylsulphonyl, carbamoyl and C.sub.1-6 alkylamino groups.