Page 151 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

138 hydrolysis, oxidation and reduction

. Magnesium sulfate

. 2 L three-necked round-bottomed flask
. Bubbler
. Thermostatically controlled oil bath and thermometer
. Orbital shaker at 30 8C and 220 r.p.m. (optional)
. Wide sinter funnel
. Magnetic stirrer plate
. Rotary evaporator
. Kugelrohr apparatus

Procedure
1. A 2 L three-necked round-bottomed flask equipped with a bubbler and a
thermometer was charged with tap water (400 mL), sucrose (75 g) and dried
yeast (10 g), added in this order. The mixture was stirred very gently
(150 r.p.m.).
After 1 hour, carbon dioxide should be evolved at approximately 1±2
bubbles/second. Alternatively the whole reaction may be carried out in a 2 L
conical-flask placed in an orbital shaker at 30 8C and 220 r.p.m.
2. Ethyl acetoacetate (5 g) was then added dropwise to the fermenting solution
and the mixture stirred at ambient temperature for 24 hours.
3. A warm solution (40 8C) of sucrose (50 g) in tap water (250 mL) was then
added and the mixture stirred for 1 hour before a further aliquot of ethyl
acetoacetate (5 g) was added. The mixture was then stirred for a further 18
hours.
4. The reaction was followed by TLC (eluent: dichloromethane). The starting
material was UV active, stained yellow with p-anisaldehyde, R f 0.75.
At this stage a very slight trace of ethyl acetoacetate could be seen by
TLC and to assist further reduction more sucrose (25 g) and yeast (10 g) were
added. The reaction was then stirred at 30 8C for 18 hours.
5. When no more starting material was apparent by TLC, the reaction was
considered to be complete.
It is essential that all the starting material is consumed before terminating
the reaction.
6. Celite 1 or hyflo super cell (20 g) was added to the suspension which was
then filtered through a pad of hyflo in a wide-sinter funnel; the pad was
washed with water (100 mL). The filtrate was saturated with sodium chloride
and then extracted with ethyl acetate (5 500 mL). The combined extracts
were dried over magnesium sulfate, filtered and the solvent was removed
under reduced pressure to afford a pale viscous oil.
7. The crude product was then distilled using Kugelrohr apparatus (56 8C,
12 mmHg) to afford the desired alcohol as a clear colourless oil (5.80 g, 57 %).
[a] 25 ‡ 35:48 (c 1.35, CHCl 3 ), [Lit. [a] 25 ‡ 37:28 (c. 1.3, CHCl 3 )] which
D D
corresponds to 80±85 % ee.