Synthesis of 4-heteryl-substituted derivatives of methylpyrazolo[1,5-a]pyrazine-4-carboxylates
Chem. Heterocycl. Compd. 2020, 56 (12), 1554-1559
Methylpyrazolo[1,5-a]pyrazine-4-carboxylates were synthesized by palladium-catalyzed carbonylation of 4-chloropyrazolo[1,5-a]-pyrazines at elevated pressure and converted via nitrile intermediates to the corresponding amidoximes and amidines. Cyclocondensation of the obtained amidoximes with trifluoroacetic anhydride or ethyl chloroformate and amidines with acetoacetate or ethyl ethoxymethylidenemalonate were used to synthesize new 4-(1,2,4-oxadiazolyl)- and 4-(pyrimidin-2-yl)-substituted pyrazolo[1,5-a]pyrazines.