HCID 178524742, compound → HCID 178516468, compound

Participants

Reaction Steps

An alternative synthesis of intermediates 19 has been described by Misra et al. (Bioorg. Med. Chem. Lett, Vol. 13(14), 2003, p. 2405). Suitably protected 4-Hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid (22, Y═OH, Z═OH) can be decarboxylated at temperatures above 200° C. Bromination of the resulting 4-Hydroxy-1H-pyrazolo[3,4-b]pyridine using elemental bromine in ethanol affords 19a (X═OH). Chlorination using phosphorus oxychloride affords 5-bromo-4-chloro-1H-pyrazolo[3,4-b]pyridine 19b (X═Cl).

Provenance & Evidence