Toluene → 5-((1R)-2-bromo-1-hydroxyethyl)-8-phenylmethoxy-1H-quinolin-2-one

Participants

Reaction Steps

8-(Benzyloxy)-5-(2-bromoacetyl)quinolin-2(1H)-one (26.0 g, 69.9 mmol) and (R)-3,3-diphenyl-1-methyltetrahydro-3H-pyrrolo[1,2-c][1,3,2]oxazaborole (21.3 g, 76.8 mmol) were azeotroped with toluene (×3) then suspended in anhydrous THF (400 mL) under an atmosphere of nitrogen. The suspension was cooled to −20° C. (external temperature), and borane dimethyl sulfide complex solution (45.4 mL, 90.8 mmol, 2.0 M solution in THF) was added by syringe pump over 3 hours. After complete addition the reaction mixture was stirred for an hour before quenching with methanol (25 mL). The reaction was warmed to RT over 20 minutes. The mixture was concentrated in vacuo and the residue was suspended in aqueous hydrochloric acid (500 mL, 1 M solution) and stirred at RT for 18 hours. After this time, the solid was collected by filtration and washed with water (×3). The solid was partially dissolved in ethyl acetate and heated at reflux for 2 hours. The remaining solid was removed by hot filtration, and the filtrate was evaporated to afford the title compound. The solid collected from the hot ethyl acetate was again partially dissolved in ethyl acetate and heated at reflux for 2 hours then filtered to give filtrate containing pure product. This process was repeated four more times. The combined solid was recrystallised from ethyl acetate and petroleum ether to afford the title compound (20.0 g, 76%).

Provenance & Evidence