Hydrazine hydrate (1:1) → 6-Fluoro-3-(2-fluorobenzyl)-1H-pyrazolo[4,3-b]pyridine

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Reaction Steps

9.07 g (32.4 mmol) of the compound from example 37A were initially charged in pyridine (84 ml). Subsequently, 8.10 g (162 mmol) of hydrazine hydrate and 19.8 mg (0.162 mmol) of 4-dimethylaminopyridine were added, and the mixture was heated to reflux for 30 min. The reaction mixture was diluted with ethyl acetate at RT and washed four times with 10% aqueous citric acid solution. The organic phase was subsequently washed with saturated aqueous sodium chloride solution, dried over sodium sulfate, filtered and concentrated. The residue was admixed with tert-butyl methyl ether and the solids were filtered off. The latter were dried under high vacuum and gave 1.79 g (79% purity, 18% of theory) of the title compound. The filtrate was concentrated and gave a further 4.86 g (61% purity, 37% of theory) of the title compound. The two fractions were combined and converted without further purification.

Provenance & Evidence