Page 137 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

124 hydrolysis, oxidation and reduction

. tert-Butylmagnesium chloride, 1.0 M THF solution, 52 mL
. Methylmagnesium chloride, 1.0 M THF solution, 112 mL
. Borane±THF complex, 1.0 M, 70 mL
. Hydrochloric acid
. Sodium chloride, sodium sulfate
. Silica gel
. n-Hexane, ethyl acetate, diethyl ether, toluene, ethyl alcohol
. (ÿ)-Sparteine, 8.7 g
. sec-BuLi 1 M in cyclohexane, 37.1 mL
. Copper(II) chloride, 6.2 g
. Aqueous ammonia
. Trifluoromethanesulfonic acid
. Potassium hydroxide
. Basic alumina
. Argon

. Magnetic stirrer
. 300 mL Round-bottomed flask with a magnetic stirrer bar
. Dropping funnel
. Separatory funnel
. Dry ice
. Schlenk tube
. Oil bath
. Rotary evaporator
. Cannula

Procedure
1. To a solution of phosphorus trichloride (6.4 g) in dry tetrahydrofuran
(20 mL) was added tert-butylmagnesium chloride (1.0 M THF solution,
52 mL) at ÿ788C under an argon atmosphere over a period of 2 hours.
2. After stirring at room temperature for 1 hour, methylmagnesium chloride
(1.0 M THF solution, 112 mL) was added at 0 8C over 30 minutes. The
reaction mixture was stirred at room temperature for 1 hour. To this solution,
borane±THF complex (1.0 M, 70 mL) was added at 0 8C, and the mixture was
stirred at the same temperature for 1 hour.
3. The reaction mixture was poured into cold 5 % hydrochloric acid (200 mL).
The organic layer was separated and aqueous layer was extracted with ethyl
acetate (3 80 mL). The combined extracts were washed with brine, dried
over sodium sulfate, and concentrated in vacuo.
4. The residual pasty solid was purified by column chromatography over silica
gel (n-hexane : ethyl acetate ˆ 8:1) to afford tert-butyl (dimethyl)phosphine±
borane (1) 5.29 g (86 %) as white crystals.
5. To a solution of (ÿ)-sparteine (8.7 g) in diethyl ether (dry, 100 mL) sec-
butyllithium (1 M in cyclohexane, 37.1 mL) was added at ÿ78 8C under an