Synthesis of 1-methyl-3-phenylpyrazolo[4,3-b]pyridines via a methylation of 4-phthalimino-3-phenylpyrazoles and optimization toward highly potent corticotropin-releasing factor type-1 antagonists

1-Methyl-3-phenylpyrazolo[4,3-b]pyridines were synthesized via a cyclization reaction of 1-methyl-4-amino-3-phenylpyrazoles 8 with ethyl acetoacetate. Optimization of this series of compounds resulted in CRF1 antagonists with subnanomolar binding affinity. Compounds bearing a polar group such as methoxy or hydroxy were also found to be very active.