Hydrochloric Acid → 5-Isobutyl-3,3-dimethyl-2,3-dihydrobenzofuran-7-boronic acid

Participants

Reaction Conditions

Reaction Steps

To a mixture of 7-bromo-5-isobutyl-3,3-dimethyl-2,3-dihydro-benzofuran (9.9 g, 34.96 mmol) in THF (50 mL) cooled to −78° C. under an atmosphere of argon was added n-BuLi (25.17 mL, 2.5 M, 62.93 mmol) dropwise. The reaction mixture was stirred for 5 minutes and triisopropylborate (24.2 mL, 104.87 mmol) was added dropwise. The mixture was stirred at −50° C. for 2 hours then warmed up to room temperature and stirred overnight at room temperature. 1.0 N HCl (100 mL) was slowly added to the reaction mixture. After 1 hour the mixture was diluted with ethyl acetate and the layers separated. The organic layer was further washed with water, brine, dried (MgSO4), filtered and evaporated. The residue was chromatographed on silica gel (0 to 20% ethyl acetate in hexane) to give 4.3 g of 5-isobutyl-3,3-dimethyl-2,3-dihydro-benzofuran-7-boronic acid (46%). 1H NMR (300 MHz; CDCL3): 0.90 (d, J=6.6 Hz, 6H), 1.33 (s, 6H), 1.81 (m, 1H), 2.43 (d, J=7.5 Hz, 2H), 4.28 (s, 2H), 5.86 (br s, 2H), 6.98 (d, J=2.1 Hz, 1H), 7.33 (d, J=2.1 Hz, 1H).

Provenance & Evidence