Method of producing 2-acyl amino 5-halogenopyridine compounds

A method of producing a 2-acylamino-5-halogenopyridine expressed by formula (II) ##STR10## wherein R.sub.1 is hydrogen or at least one lower alkyl group connected to a 4-position and/or 6-position, R.sub.2 is an alkyl group or an unsubstituted or substituted phenyl group, and X is a halogen, said method comprising the steps of

• halogenating a 2-acylaminopyridine expressed by formula (I), ##STR11## wherein R.sub.1 and R.sub.2 are defined in the same manner as in formula (II), in the presence of a buffer which maintains the pH at about neutral during the halogenation reaction by dissolving the 2-acylaminopyridine of formula (I) in at least one selected solvent system and adding a molecular halogen and a buffer which maintains the pH of the mixture at about neutral during the halogenation reaction to the dissolved 2-acylaminopyridine.