Organic Syntheses, CV 5, 70
Submitted by Knud Pedersen, Preben Jakobsen, and Sven-Olov Lawesson
1.
Checked by R. Schöllhorn and R. Breslow.
1. Procedure
Caution! This reaction should be carried out behind a safety screen. The solvent removal and product distillation steps should also be carried out behind a screen to minimize danger due to contamination of the product with undetected peroxides.
A
250-ml., three-necked, round-bottomed flask equipped with a
sealed mechanical stirrer, a
reflux condenser, and a
pressure-equalizing dropping funnel is set up for conducting a reaction in an atmosphere of
nitrogen by fitting into the top of the condenser a T-tube attached to a low-pressure supply of
nitrogen and to a
mercury bubbler. In the flask are placed
41 g. (0.50 mole) of cyclohexene and
0.05 g. (0.00035 mole) of cuprous bromide, and the mixture is heated in an
oil bath at 80–82°. When the temperature of the mixture reaches that of the oil bath,
40 g. (0.21 mole) of t-butyl perbenzoate (Note
1) is added dropwise with stirring over a 1-hour period, during which the color of the now homogeneous solution becomes blue. Stirring and heating are continued for an additional 3.5 hours (Note
2). The cooled reaction mixture is washed with two
50-ml. portions of dilute aqueous sodium carbonate to remove
benzoic acid (Note
3). The remaining organic phase is washed with water until neutral and dried over anhydrous
sodium sulfate. The excess of
cyclohexene is removed by distillation under reduced pressure, and the residue (Note
4) is distilled through a
short Vigreux column to give
29–33 g. (
71–80%) of
3-benzoyloxycyclohexene, b.p.
97–99° (0.15 mm.),
n20D 1.5376–1.5387 (Note
5).
2. Notes
1.
t-Butyl perbenzoate is supplied by Lucidol Division, Wallace and Tiernan, Inc., Buffalo 5, New York, or L. Light and Co., Ltd., Colorbrook, Bucks, England. The Lucidol product contains
98% t-butyl perbenzoate.
2. The progress of the reaction can most conveniently be followed by periodic examination of the infrared spectrum of the mixture (ν
C=O for peroxybenzoate: 1775 cm.
−1). After all of the perester has been added,
ca. 3 hours is required for its consumption.
3. After acidification of the aqueous phase
1.5–2 g. of benzoic acid can be isolated.
4. It is recommended that an infrared spectrum be run on the residue before the distillation to check for the absence of perester (Note
2).
5. The same yield is obtained when the scale is increased threefold.
3. Discussion
The procedure is that of Kharasch, Sosnovsky, and Yang.
2
4. Merits of the Preparation
The reaction described is of considerable general utility for the preparation of benzoyloxy derivatives of unsaturated hydrocarbons.
2,3,4,5,6,7,8 Reactions of
t-butyl perbenzoate with various other classes of compounds in the presence of catalytic amounts of copper ions produce benzoyloxy derivatives. Thus this reaction can also be used to effect one-step oxidation of saturated hydrocarbons,
9,10 esters,
5,11 dialkyl and aryl alkyl ethers,
12,13,14 benzylic ethers,
11,15 cyclic ethers,
13,16 straight-chain and benzylic sulfides,
12,17,18,19 cyclic sulfides,
11,19 amides,
11 and certain organosilicon compounds.
20 Reviews
20,21 of these reactions are available.
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