Page 78 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

epoxidation of a, b-unsaturated carbonyl compounds 63

Materials and equipment

. (1S,2S)-N-Methylpseudoephedrine, 430 mg, 2.4 mmol, 2.4 eq
. Anhydrous toluene, 12 mL
. Diethylzinc solution, 1.1 M in toluene, 1 mL, 1.1 mmol, 1.1 eq

Diethylzinc is flammable, reacts with water and can cause severe burns.
Wear gloves and eye protection, and handle with care.
If low yield and/or enantiomeric excess is obtained, the purity of the di-
ethylzinc should be the primary suspect.
. Oxygen gas
. 2-Isobutylidene-1-tetralone, 200 mg, 1 mmol
This substrate was prepared by aldol condensation of tetralone with iso-
[9]
butyraldehyde in the presence of aqueous sodium hydroxide .
. Aqueous phosphate buffer solution pH 7, 8 mL
. Dichloromethane, petroleum ether, diethyl ether, n-hexane
. Brine
. Sodium sulfate
. Silica gel 60 (0.063±0.04 mm)
. p-Anisaldehyde

. 50 mL Two-necked dry flask with a magnetic stirrer bar
. Magnetic stirrer
. Acetone cooling bath equipped with a contact thermometer, 0 8C
. Syringes
. Balloon equipped with a syringe
. Ice-bath
. Separating funnel, 250 mL
. Rotary evaporator

Procedure
1. A 50 mL two-necked flask, equipped with a magnetic stirrer bar, was placed
in an oven at 120 8C for 4 hours. The flask was removed, cooled under
vacuum and flushed with nitrogen.
2. In the dry flask was dissolved (1S, 2 S)-N-methylpseudoephedrine (430 mg) in
anhydrous toluene (10 mL) under argon. The reaction mixture was placed in a
cooling bath equipped with a contact thermometer stirred and cooled to 0 8C.
Diethylzinc (1 mL) was added carefully via a syringe (evolution of ethane).
3. After 80 minutes the connection with argon was replaced by a balloon
filled with oxygen. The reaction mixture was stirred for 2.5 hours without
removing the balloon filled with oxygen.
4. The bath was cooled to ÿ78 8C and a solution of 2-isobutylidene-1-tetralone
(200 mg) in anhydrous toluene (2 mL) was added via a syringe to the cold
mixture. The reaction mixture was stirred at this temperature for 30 minutes