(2,4-Difluoro-phenyl)-hydrazine → 1-(2,4-Difluorophenyl)-4-iodo-1H-pyrazolo[3,4-B]pyridine

Participants

Reaction Steps

To a dry 16×100 mm Chem-Glass reaction tube under N2 was added 2-fluoro-4-iodonicotinaldehyde (5 g, 19.92 mmol), (2,4-difluorophenyl)hydrazine (3.01 g, 20.92 mmol) and anhydrous NMP (35 mL). The reaction mixture was flushed with argon, securely capped, stirred for 20 min at room temp, and then placed in a 180° C. oil bath for 4 h. The reaction mixture was then allowed to stir at room temperature for 72 h. The reaction mixture was diluted with EtOAc (1200 mL) and the organic layer was extracted with water (6×350 mL), brine (1×100 mL), dried over Na2SO4, filtered, and evaporated to dryness. The residue was purified by Biotage Silica gel chromatography on a 300 g Thompson Single Step™ silica cartridge using a linear gradient from 100% hexanes to 100% dichloromethane over 10 column volumes to give 4.53 g (44.6%) of Intermediate 13A, as a light yellow solid that contained 28% of the uncyclized hydrazone intermediate ((E)-3-(2-(2,4-difluorophenyl)hydrazono)methyl)-2-fluoro-4-iodopyridine). 1H NMR (500 MHz, CCl3D) δ ppm 8.21 (1 H, d, J=4.58 Hz), 8.14 (1 H, s), 7.59-7.71 (2 H, m), 7.10 (2 H, td, J=7.55, 3.81 Hz). LC/MS (Condition A): T=3.7 min, (M+H)+ 357.90.

Provenance & Evidence