Carbon Dioxide → HCID 59490926, compound

Participants

Reaction Steps

A solution of 5-bromo-6-fluoro-1H-indazole (29D, 3.50 g, 16.28 mmol) in tetrahydrofuran (200.00 mL) was treated with sodium hydride (60% in mineral oil, 1.172 g) at 0° C. and stirred at room temperature for 20 minutes. The reaction mixture was cooled to −78° C. (dry ice and acetone) and treated with 2.5 M of n-butyl lithium in hexane (8.2 mL, 20.3 mmol) dropwise. The reaction mixture was stirred at that temperature for 20 minutes and treated with DMF (5.06 mL, 65.11 mmol). The reaction mixture was slowly warmed to room temperature when the viscous solution turn fluidic and stirring was efficient. Analysis of TLC (40% EtOAc/Hexanes) indicated complete conversion of starting material to product. The reaction mixture was acidified with aq. HCl taken up in EtOAc (500 mL) washed with aq. HCl (100 mL), brine (100 mL), dried (MgSO4), filtered, concentrated in vacuo and used as it is in next step. A solution of product 6-fluoro-1H-indazole-5-carbaldehyde (2.3 g) in THF (100 mL) was treated with di-tort-butyldicarbonate (3.56 g, 16.28 mmol) and DMAP (300 mg) and stirred at room temperature for 3 hours. The reaction mixture was concentrated in vacuo and the residue was purified using chromatography (SiO2, EtOAc/Hexanes gradient 0-40%) to yield [2e] tert-butyl 6-fluoro-5-formyl-1H-indazole-1-carboxylate (29E, 3.5 g; Yield=81%) as a colorless solid.

Provenance & Evidence