Triisopropyl borate → 3-cyano-1-cyclobutyl-6-(difluoromethoxy)-1H-indol-2-ylboronic acid

Participants

Reaction Conditions

Reaction Steps

Into a solution of 1-cyclobutyl-6-(difluoromethoxy)-1H-indole-3-carbonitrile (1.5 g, 5.7 mmol) and triisopropyl borate (2.4 mL, 10.3 mmol) in THF (25 mL) at −78° C. was added LDA (1.5 M in cyclohexane, 5.0 mL, 7.5 mmol). The mixture was stirred at −78° C. for 30 min and then quenched with ice water (60 mL) and stirred for 15 min without cooling. The mixture was extracted with ethyl acetate 1:1 in hexane (20 mL). The aqueous layer was acidified with 2 N aq. HCl to pH 5 and extracted with CH2Cl2 (60 mL). The organic layer was dried over Na2SO4 and concentrated to give 3-cyano-1-cyclobutyl-6-(difluoromethoxy)-1H-indol-2-ylboronic acid as a solid (1.8 g, 60% pure by LCMS) that was used in the next step without further purification.

Provenance & Evidence