Carbon Dioxide → 5-chloro-1H-indazole-7-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

463 mg (2 mmol) of 7-bromo-5-chloro-1H-indazol were dissolved in 12 ml THF. The so-lution was cooled to −78° C. under argon. 3.75 ml (6 mmol) of a 1.6 M butyl lithium solution in hexane were added slowly within 10 min. The reaction mixture was warmed to 5° C. and stirred for 30 min at this temperature. A suspension was obtained, which was cooled to −78° C. Solid carbon dioxide was added and the reaction mixture was warmed to rt. At 10° C. the suspension became a clear solution. The solvent was evaporated and the residue was treated with water and diethyl ether. The aqueous layer was extracted once with diethyl ether, acidified with 1N aqueous HCl solution. A white solid precipitated, which was filtered off and washed with water. The solid was suspended in diethyl ether/heptane in order to remove pentanoic acid. 130 mg (33%) of 5-chloro-1H-indazole-7-carboxylic acid were obtained as a white solid after filtration and drying. MS (ISP) 195.1 (M−H)−.

Provenance & Evidence