Triisopropyl borate → (5-(Cyclopropylcarbamoyl)-3-fluoro-2-methylphenyl)boronic acid

Participants

Reaction Conditions

Reaction Steps

N-Cyclopropyl-5-fluoro-3-iodo-4-methylbenzamide (Intermediate 37, 5 g) in THF (75 ml) was cooled to 0° C. and sodium hydride (60%, 1.23 g) added portionwise over 10 minutes. Once effervescence had ceased the reaction was cooled to −75° C. and n-butyl lithium (1.6M in hexanes, 20 ml) added over 25 minutes maintaining a temperature of <−70° C. Triisopropyl borate (8 ml) was added to the reaction over 10 minutes and the reaction stirred at −70° C. for 4 hours. The reaction was quenched with water (20 ml) and the mixture allowed to warm to 5° C. The reaction was concentrated under vacuum and the residue partitioned between saturated ammonium chloride and ethyl acetate. The organic phase was washed with saturated ammonium chloride, brine, dried (sodium sulphate) and reduced to dryness under vacuum. The residue was dissolved in DCM/ethyl acetate and purified by column chromatography on silica eluting with an ethyl acetate/DCM gradient (5–100% ethyl acetate) and then methanol. The product fractions were combined and the solvent evaporated under vacuum to give {5-[(cyclopropylamino)carbonyl]-3-fluoro-2-methylphenyl}boronic acid. LCMS MH+ 238, retention time 2.19 min.

Provenance & Evidence