Page 71 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

56 hydrolysis, oxidation and reduction

Materials and equipment

. a, b-Unsaturated ketone, 2 mmol
. Sodium hydroxide, 100 mg, 2.5 mmol, 1.25 eq
. Anhydrous methanol, 10 mL
. Solution of 30 % of hydrogen peroxide, 300 mg, 2.5 mmol, 1.25 eq
Hydrogen peroxide can cause burns: wear suitable protective clothing,
including eye and face protection. Store in a cool place.
. Brine
. Dichloromethane
. Magnesium sulfate
. Silica gel 60 (0.063±0.04 mm)

. 50 mL Round-bottomed flask with a magnetic stirrer bar
. Magnetic stirrer
. Separating funnel, 250 mL
. Rotary evaporator

Procedure
1. In a 50 mL dry round-bottomed flask was dissolved the a, b-unsaturated
ketone (2 mmol) in anhydrous methanol (10 mL); hydrogen peroxide
(300 mg) was added.
2. The reaction mixture was stirred at room temperature and the reaction
monitored by TLC. After completion, the reaction was carefully quenched
with water (10 mL). A white precipitate appeared.
3. The reaction mixture was transferred into a separating funnel and the aqueous
layer extracted with dichloromethane (3 30 mL). The combined organic
layers were washed with water (3 30 mL) and then with brine (30 mL), dried
over magnesium sulfate, filtered and concentrated under reduced pressure.
4. The residue was purified by flash chromatography on silica gel as required.
(See below for the purification methods for each substrate.)

4.2 ASYMMETRIC EPOXIDATION USING POLY-d-LEUCINE
d
Bentley et al. [1] recently improved upon Julia Â's epoxidation reaction. By using
urea±hydrogen peroxide complex as the oxidant, 1,8-diazabicyclo[5,4,0]undec-
7-ene (DBU) as the base and the Itsuno's immobilized poly-d-leucine
(Figure 4.2) as the catalyst, the epoxidation of a, b-unsaturated ketones was
carried out in tetrahydrofuran solution. This process greatly reduces the
time required when compared to the original reaction using the triphasic
conditions.