Page 106 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

92 hydrolysis, oxidation and reduction

Procedure

1. A solution was prepared by mixing an aqueous solution of sodium hydro-
genphosphate (0.05 M, 10 mL) and a solution prepared with concentrated
bleach (sodium hypochlorite, 5 mL) in water (20 mL). The pH of the
resulting solution was adjusted to 11.25 by addition of few drops of hydro-
gen chloride 1 M or sodium hydroxide 1 M.
2. A 100 mL flask, was filled with (Z)-ethyl cinnamate, (666 mg of the mixture
containing 75 % of (Z)-ethyl cinnamate), 4-phenylpyridine N-oxide (116 mg)
and dichloromethane (6 mL). Jacobsen's catalyst (108 mg) was then added.
3. The resulting organic solution and the buffered bleach (16 mL) were cooled
separately using an ice-bath and then combined at 4 8C in the flask.
4. 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, 9:1). (Z)-Ethyl cinnamate was UV
active, R f 0.42. The epoxide visualized with p-anisaldehyde dip stained yellow,
R f 0.28.
5. After 12 hours of stirring the two-phase mixture at room temperature, the
reaction was quenched. The reaction mixture was transferred into a 100 mL
beaker, tert-butyl methyl ether (50 mL) was added and the solution was
stirred for 10 minutes.
6. The mixture was transferred into a separating funnel. The aqueous phase
was separated and extracted with tert-butyl methyl ether (2 20 mL). The
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brown combined organic layers were filtered through a pad of Celite , and
then washed with water (2 40 mL) and with brine (2 40 mL), dried over
sodium sulfate, filtered and concentrated under reduced pressure, giving a
brown oil (700 mg).
7. The crude material was purified by flash chromatography on silica gel
(20 g) using petroleum ether±ethyl acetate (95:5) as eluent to give a yellow oil
(286 mg) which was amixture of 77 % (Z)-ethyl 3-phenylglycidate (1.14 mmol,
45 % yield) and 23 % of (E)-ethyl 3-phenylglycidate (0.34 mmol).
The ee (91.5 %) was determined by GC analysis (Lipodex 1 C 25 m,
0.25 mm ID, temperatures: column 110 8C isotherm, injector 250 8C, de-
tector 250 8C, mobile phase helium). (1R, 2R)-(Z)-enantiomer: R t 41.4 min,
(1S,2S)-(Z)-enantiomer: R t 42.6 min.
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(Z)-Ethyl 3-phenylglycidate H NMR (200 MHz, CDCl 3 ): d 7.42±7.30
(m, 5H, Ph); 4.27 (d, J 4.4 Hz, 1H, CH); 4.01 (q, J 7.15 Hz, 2H, CH 2 ); 3.83
(d, J 4.4 Hz, 1H, CH); 1.02 (t, J 7.15 Hz, 3H, CH 3 ).
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(E)-Ethyl 3-phenylglycidate H NMR (200 MHz, CDCl 3 ): d 7.42±7.30
(m, 5H, Ph); 4.291 (q, J 7.15 Hz, 2H, CH 2 ); 4.09 (d, J 1.65 Hz, 1H, CH); 3.51
(d, J 1.65 Hz, 1H, CH); 1.33 (t, J 7.15 Hz, 3H, CH 3 ).
ÿ1
IR (CHCl 3 , cm ): 3070 (C±H epoxide), 3012 (C±H aromatic), 2988,
2943, 2911, 2876 (C±H aliphatic), 1748 (CˆO), 1455 (CˆC), 1416, 1375
(CH 2 , CH 3 ), 1394, 1301 (C±O), 1190 (C±O±C)), 1108, 1052, 1027, 917.
Mass: calculated for C 11 H 12 O 3 : m/z 192.07864; found [M] ‡ 192.07855.