Organic Syntheses, CV 6, 218
Submitted by Ned M. Weinshenker
1, Chah M. Shen, and Jack Y. Wong.
Checked by A. Fukuzawa and S. Masamune.
1. Procedure
Caution!
Benzene has been identified as a carcinogen; OSHA has issued emergency standards on its use. All procedures involving
benzene should be carried out in a
well-ventilated hood, and glove protection is required
A
250-ml., three-necked, round-bottomed flask equipped with a
mechanical stirrer, a
gas-inlet, and a
stopper is charged with
540 mg. (0.00346 mole) of a mixture of cis- and trans-4-tert-butylcyclohexanols (Note
1),
50 ml. of anhydrous benzene (Note
2), and
25 ml. of anhydrous dimethyl sulfoxide (Note
3). While a slight positive pressure of
argon is maintained in the system,
13.19 g. of carbodiimide resin (Note
4) is added, followed by
0.2 ml. of dimethyl sulfoxide (Note
3) containing
98 mg. (0.0010 mole) of anhydrous orthophosphoric acid (Note
5). The resulting mixture is stirred at room temperature for 3.5 days. The beads are then separated by filtration and washed with three
100-ml. portions of diethyl ether, and the combined filtrates are washed with five 100-ml. portions of water. After evaporation of the organic phase to dryness, the residue crystallizes, providing
446–450 mg. (
83–84%) of crude
4-tert-butylcyclohexanone, m.p.
42–45° (Note
6). The deactivated
carbodiimide resin can be regenerated by treatment with
triethylamine and
4-toluenesulfonyl chloride (Note
4).
2. Notes
1. This mixture is available from Aldrich Chemical Company, Inc. The checkers used a 7:93 mixture of the
cis- and
trans-isomers, prepared by
lithium aluminum hydride reduction of
4-tert-butylcyclohexanone and recrystallization of the crude product. The
ketone was purchased from Aldrich Chemical Company, Inc.
The submitters added
5.88 ml. of 85% phosphoric acid to
3.98 g. of phosphorous pentoxide and heated the mixture for 15 minutes or until all of the solid had dissolved. The checkers placed
71.0 g. of phosphorous pentoxide in a flask, cooled it in ice, and cautiously added 27 ml. of water.
6. IR(CHCl
3) cm.
−1: 1712 (C=O). GC analysis (10% Carbowax 20M, 3 mm. by 1.8 m., 180°) showed the crude product to be 97% pure.
4-tert-Butylcyclohexanone has been reported to melt at
49.5–51°.
2
3. Discussion
The general procedure described here was originally published by the submitters.
3 Both ketones and aldehydes may be prepared, and this method is particularly effective when the mild conditions of the Moffat oxidation are required, but the
dicyclohexylurea by-product formed with the usual reagents causes purification problems.
This preparation is referenced from:
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