Triisopropyl borate → [5-Methoxy-2-(trifluoromethoxy)phenyl]boronic acid

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of 2-Bromo-4-methoxy-1-trifluoromethoxy-benzene (Preparation 59, 19.0 g, 73.9 mmol) in anhydrous tetrahydrofuran (400 ml) was added n-butyl lithium (2.5M solution in hexanes, 44.2 ml, 110.9 mmol) while maintaining the temperature below −70° C. under an atmosphere of nitrogen. The resulting solution was stirred at −70° C. for 1 hour. Tri-isopropyl borate (20.9 g, 110.9 mmol) was added and the mixture stirred at −70° C. for an additional 2 hours. The reaction mixture was quenched with saturated ammonium chloride aqueous solution (400 ml). The resulting mixture was acidified to pH˜5 by addition of hydrochloric acid (1N aqueous solution). The layers were separated and the organic layer was washed with water (200 ml) then dried over anhydrous MgSO4 (s), filtered and evaporated in vacuo. Residue was purified by recrystallization from ethyl acetate:petroleum ether (2 ml:50 ml) to afford the title compound as a white solid (7.5 g, 43%).

Provenance & Evidence