2-Fluoro- and 2,6-difluoropyridine are readily quaternised with methyl p-toluenesulfonate and methyl triflate respectively. These salts readily undergo substitution of fluorine by enamines, the difluoro-derivatives being capable of specific mono- or disubstitution in a symmetrical or unsymmetrical manner. The products reduced to give keto-1,2,3,6-tetrahydropyridines, can be hydrolysed to the corresponding ketopyridines or hydrogenated to give ketopiperidines.