SYNTHESIS OF 5-AMINO-1H-PYRAZOLO[4,3-b]PYRIDINE DERIVATIVES AND ANNULATION OF IMIDAZOLE AND PYRIMIDINE RINGS THERETO

Abstract

1-Alkyl-N-Boc-5-formylpyrazol-4-amines react with malononitrile and cyanoacetamide to form 5-amino-1H-pyrazolo[4,3-b]pyridine nitriles and amides, respectively. Cyclocondensation of the obtained derivatives with chloroacetaldehyde, bromotrifluoroacetone, or ethyl bromopyruvate leads to the formation of imidazo[1,2-a]pyrazolo[3,4-e]pyridines or to pyrazolo[3',4',5,6]pyrido[2,3-d]pyrimidine derivatives in cyclocondensation with orthoesters, ethyl oxalyl chloride, or carbonyldiimidazole.