Org. Synth. 1967, 47, 34
DOI: 10.15227/orgsyn.047.0034
CYCLOHEXYLIDENECYCLOHEXANE
[Bicyclohexylidene]
Submitted by Nicholas J. Turro
1, Peter A. Leermakers
2, and George F. Vesley
2.
Checked by Alex G. Fallis and Peter Yates.
1. Procedure
A. Dispiro[5.1.5.1]tetradecane-7,14-dione. Cyclohexanecarbonyl chloride (Note 1) (30.0 g., 0.205 mole) and 250 ml. of dry benzene are placed in a three-necked, round-bottomed flask equipped with a stirrer, condenser, and dropping funnel. A nitrogen atmosphere is maintained in the system. Dry triethylamine (35.0 g., 0.35 mole) is slowly added, and the mixture is heated under reflux overnight. The amine hydrochloride is then filtered, and the filtrate is washed with dilute hydrochloric acid and with water. Solvent is removed on a steam bath, and the residue is recrystallized from ligroin-ethanol; yield 11–13 g. (49–58%), m.p. 161–62°.
B. Cyclohexylidenecyclohexane. In a Hanovia 450-watt immersion photochemical reactor (Note 2), equipped with a side arm attachment to monitor gas evolution, is placed 15 g. (0.068 mole) of dispiro[5.1.5.1]tetradecane-7,14-dione dissolved in 150 ml. of methylene chloride. The sample is irradiated, and carbon monoxide starts to evolve rapidly after a few minutes. Irradiation is continued until gas evolution has ceased, usually about 8–10 hours (Note 3). After the irradiation most of the solvent is removed on a steam bath. The residual oil is transferred to a sublimator. The sublimator, with the cold finger removed, is placed in a vacuum desiccator, and the system is evacuated to remove any remaining methylene chloride. The semisolid residue is then sublimed at 45° (1 mm.) to yield 7 g. (63%) of crude cyclohexylidenecyclohexane. The product after recrystallization from methanol weighs 5.5 g. (49%), m.p. 53–54°.
2. Notes
1.
Cyclohexanecarbonyl chloride was obtained from Eastman Organic Chemicals.
2.
The reactor, manufactured by the Hanovia Division of Engelhard Industries, consists of a water-jacketed Vycor well through which a stream of water is continuously passed. Since wavelengths shorter than 3000 Å are not needed, the immersion well may be made of Pyrex instead. Within the well is a No. 679A-36 450-watt medium-pressure mercury lamp, also manufactured by Hanovia, and a cylindrical Pyrex filter which surrounds the lamp. The well is placed in an appropriately shaped flask containing the solution to be irradiated. The flask is essentially cylindrical and is equipped with a side arm near the top through which gas can escape and be bubbled through a container of water. The flask is so designed that the liquid level is above the top of the lamp. The reaction vessel is quite similar to that shown in
Fig. 1 (p. 65).
The same synthesis could be carried out in an ordinary flask using one or two sunlamps or sunlight, but the irradiation time would necessarily be much longer.
3.
The system should be relatively free of
oxygen during irradiation.
Oxygen apparently combines with a photochemical intermediate to form
cyclohexanone.
3 Under the conditions recommended in the procedure,
oxygen is prevented from entering the system by the
water trap which also serves as a monitor for gas evolution.
3. Discussion
Ethyl 1-bromocyclohexanecarboxylate, when treated with
magnesium in anhydrous
ether-benzene with subsequent addition of
cyclohexanone, yields
ethyl 1-(1-hydroxycyclohexyl)cyclohexanecarboxylate. Dehydration and saponification give rise to
1-(1-cyclohexenyl)cyclohexanecarboxylic acid, which upon decarboxylation at 195° yields
cyclohexylidenecyclohexane in
8% overall yield, m.p.
54°.
4 This olefin has also been prepared by the debromination of
1,1'-dibromobicyclohexyl with
zinc in
acetic acid.
5
The preparation of the
dispiro[5.1.5.1]tetradecane-7,14-dione intermediate is essentially that of Walborsky and Buchman.
64. Merits of the Preparation
The most obvious features of this synthesis are its simplicity and overall yield, which appear to be superior to those of any other published report. An important merit lies in the generality of the reaction, and the fact that it is an example of a reasonably large-scale photochemical preparation.
Tetramethylethylene is readily produced from commercially available
tetramethyl-1,3-cyclobutanedione by an identical route.
7This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ligroin-ethanol
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
Benzene (71-43-2)
methanol (67-56-1)
ether (60-29-7)
carbon monoxide (630-08-0)
magnesium (7439-95-4)
Cyclohexanone (108-94-1)
oxygen (7782-44-7)
nitrogen (7727-37-9)
zinc (7440-66-6)
methylene chloride (75-09-2)
tetramethylethylene (563-79-1)
tetramethyl-1,3-cyclobutanedione (933-52-8)
triethylamine (121-44-8)
cyclohexanecarbonyl chloride (2719-27-9)
Cyclohexylidenecyclohexane,
Bicyclohexylidene (4233-18-5)
Dispiro[5.1.5.1]tetradecane-7,14-dione (950-21-0)
Ethyl 1-bromocyclohexanecarboxylate
ethyl 1-(1-hydroxycyclohexyl)cyclohexanecarboxylate
1-(1-cyclohexenyl)cyclohexanecarboxylic acid
1,1'-dibromobicyclohexyl
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