A regiospecific synthesis of both positional isomers of 4,6-disubstituted 2-dicyanomethylene-1, 2-dihydropyridin- 3-carbonitriles

A protocol allowing the regiospecific synthesis of both positional isomers of 4,6-disubstituted 2-dicyanomethylene-1,2-dihydropyridin-3-carbonitriles, precursors of 1,6-naphthyridines, is presented. Thus, treatment of enaminoketones with the propanedinitrile dimer yields one regioisomer while the treatment of the corresponding (3-chloro-allylidene)-dimethylammonium perchlorates (easily obtained from enaminoketones and POCl₃), in which the nature of the reactive centers is inverted with respect to the enaminoketone, yields the other regioisomer.