Hydrochloric Acid → (R)-1-(5-bromopyridin-3-yl)ethanol

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

A solution of (S)-(−)-α,α-diphenyl-2-pyrrolidinemethanol (253 mg, 1 mmol) and trimethyl borate (0.135 mL, 1.2 mmol) in tetrahydrofuran (10 mL) was stirred at room temperature for 1 hour after which time borane-methylsulfide complex (10 mL, 2M in tetrahydrofuran, 20 mmol) was added in one portion and the mixture cooled to 0° C. A solution of 3-acetyl-5-bromopyridine (2 g, 10 mmol) in tetrahydrofuran (10 mL) was added dropwise over 2 hours at 0° C. and then the mixture was allowed to warm to room temperature and was stirred overnight. After this time dilute aqueous hydrochloric acid (2M, 90 mL) was added with initial cooling and the mixture was stirred at room temperature for 2 hours. Dimethyl sulfide and tetrahydrofuran were removed under reduced pressure and the resulting yellow solution was basified to pH 11 with aqueous ammonia, extracted with ethyl acetate (3×50 mL) and the extracts washed with brine (50 mL), dried (MgSO4) and concentrated under reduced pressure to give (1R)-1-(5-bromopyridin-3-yl)ethanol (1.9 g) in acceptable purity.

Herkunft & Nachweise