Synthesis of pyrazolo[1,5-a]pyrazin-4-ylacetonitriles and their annulation with pyridine ring

A reaction of 4-chloropyrazolo[1,5-a]pyrazines with tert-butyl cyanoacetate proceeded via the formation of tert-butyl cyano(pyrazolo-[1,5-a]pyrazin-4(5H)-ylidene)ethanoates as intermediates and led to pyrazolo[1,5-a]pyrazin-4-ylacetonitriles, which were used to obtain derivatives of a new pyrazolo[1,5-a]pyrido[2,1-c]pyrazine system.