Process for making pyrazines from 2-aza-1,3-butadienes

Abstract

Process for the preparation of an amino-pyrazine falling within the formula: ##SPC1## In which R.sub.1 and R.sub.2 each represent a hydrogen atom, or an alkyl or aryl group, or together with the carbon atoms of the pyrazine ring form a cyclic hydrocarbon having 5 to 7 carbon atoms, and X represents a cyano, carboxy, carbonamido, alkoxy-carbonyl or aryloxycarbonyl group which comprises subjecting a 2-aza-1,3-butadiene of the general formula: ##EQU1## wherein Z and Zi each represent an alkyl group or together with the nitrogen atom form a heterocyclic compound possibly containing another hetero atom to the action of ammonia and reacting the 4-amino-2-aza-1,3-butadiene of formula ##EQU2## thus obtained with a basic agent: novel compounds of formula VIII in which R.sub.1 and R.sub.2 each represent a different alkyl or aryl group or together with the carbon atoms of the pyrazine ring form a cyclic hydrocarbon containing 5 to 7 carbon atoms: intermediate compounds of formula: ##EQU3## wherein X, R.sub.1 and R.sub.2 have the meanings given above and Z and Z' each represent an alkyl group or together with the nitrogen atom form a heterocyclic compound possibly containing another hetero-atom; and intermediate compounds of the formula: ##EQU4## wherein X, R.sub.1 and R.sub.2 have the meanings given above.