Page 104 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

90 hydrolysis, oxidation and reduction

bleach (sodium hypochlorite, 2.5 mL) in water (10 mL). The pH of the
resulting solution was adjusted to pH 11.3 by addition of few drops of
hydrogen chloride 1 M or sodium hydroxide 1 M. This solution was cooled
using an ice-bath.
2. A 100 mL flask was filled with Jacobsen's catalyst (26 mg), (Z)-methyl
styrene (1 mmol) and dichloromethane (1 mL). The solution was cooled
with an ice-bath. To this solution was added the cold solution of bleach
previously prepared (3.5 mL).
3. After 5 minutes the cooling bath was removed and the two-phase reaction
mixture was stirred at room temperature. The reaction was monitored by TLC
(eluent: petroleum ether±diethyl ether, 8:2). (Z)-Methyl styrene was UV
active, R f 0.85. The epoxide visualized with p-anisaldehyde dip stained yellow,
R f 0.63.
4. After 2 hours the reaction was quenched. The reaction mixture was trans-
ferred into a 100 mL beaker, n-hexane (10 mL) was added and stirred for 10
minutes.
5. The mixture was transferred into a separating funnel. The lower aqueous
phase was separated and extracted with n-hexane (4 20 mL). The brown
combined organic layers were washed with water (3 30 mL) and twice with
brine (2 30 mL), dried over sodium sulfate, filtered and concentrated
under reduced pressure, giving a brown oil (180 mg).
In case of formation of an emulsion, this solution was mixed with the
aqueous layer and extracted with n-hexane as explained in the earlier pro-
cedure.
6. The crude material was purified by flash chromatography on silica gel
(20 g) buffered with 1 % triethylamine, using petroleum ether±ethyl acetate
(9:1) as eluent to give the epoxide as a grey oil (104 mg, 0.78 mmol, 78 %
yield).
The ee (90.5 %) was determined by GC analysis (Lipodex 1 E 25 m,
0.25 mm ID, temperatures: column 110 8C isotherm, injector 250 8C, de-
tector 250 8C, mobile phase helium); (1S,2R)-enantiomer: R t 7.8 min, (1R,
2S)-enantiomer: R t 9.0 min.
1 H NMR (200 MHz, CDCl 3 ): d 7.35±7.31 (m, 5H, Ph); 4.07 (d, J 4.4 Hz,
1H, CH); 3.35 (qd, J 5.5 Hz, J 4.4 Hz, 1H, CH±CH 3 ); 1.09 (d, J 5.5 Hz, 3H,
CH 3 ).
ÿ1
IR (CHCl 3 , cm ): 3091, 3069 (C±H epoxide), 3008 (C±H aromatic),
2972, 2934, 2877 (C±H aliphatic), 1730, 1604, 1495, 1451 (CˆC), 1416,
1375, 1359, 1248 (C±OH, C±O±C), 1028, 1009, 955, 915, 851.
Mass: calculated for C 9 H 14 NO: m/z 152.10754; found [M ‡ NH 4 ] ‡
152:10743.