反应详情

5-Nitro-1H-pyrazole-3-carboxylic acid 1 is reduced under standard conditions, such as treatment with hydrogen in the presence of palladium(0) on carbon in a solvent such as methanol, to yield 5-amino-1H-pyrazole-3-carboxylic acid 2. Compound 2 is reacted with di-aldehyde 3, carrying a bromo or chloro substituent at the R1 position, under acid conditions, such as acetic acid, at elevated temperatures to give 6-bromo- or 6-chloro-pyrazolo[1,5-a]pyrimidine-2-carboxylic acid (4). A compound of Formula I is prepared from 4 via reaction with an appropriate secondary amine 5 in the presence of a condensation agent, including, for example, O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (“TBTU”) or N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC).