The acid chloride (II) of isonicotinic acid is prepared by reaction of oxalyl chloride (A) with the potassium salt of isonicotinic acid (I). The acylation of 1,3-dihydro-4-ethyl-2H-imidazol-2-one (III) with acid chloride (II) under Friedel-Crafts' conditions gives 1,3-dihydro-4-isonicotinoyl-5-ethyl-2H-imidazol-2-one.