Novel Regioselective Preparation of 5-Chloropyrazine-2-Carbonitrile from Pyrazine-2-Carboxamide and Coupling Study of Substituted Phenylsulfanylpyrazine- 2-Carboxylic Acid Derivatives

A new method of 5-chloropyrazine-2-carbonitrile preparation in a regioselective fashion and the study of the coupling of the pyrazine ring with variously substituted benzenethiols are described. A radical-ionic mechanism of this coupling, carried out in the presence of a heterogeneous copper catalyst, has been proposed. The reactivity of the substituted chloropyrazines is correlated to the calculated values of electronic deficiency in positions C(6) or C(5) or C(3) of the pyrazine ring. This nucleophilic substitution provided a series of substituted phenylsulfanylpyrazine-2- carboxylic acid derivatives. The synthetic approach, analytical and spectroscopic data of all compounds are presented.