Org. Synth. 1959, 39, 37
DOI: 10.15227/orgsyn.039.0037
METHYL CYCLOPENTANECARBOXYLATE
[Cyclopentanecarboxylic acid, methyl ester]
Submitted by D. W. Goheen and W. R. Vaughan
1.
Checked by N. J. Leonard, M. J. Konz, W. H. Pittman, and K. L. Rinehart, Jr..
1. Procedure
A dry
1-l. three-necked, round-bottomed flask is equipped with an efficient stirrer (Note 1), a
spiral reflux condenser, and a
dropping funnel, and all openings are protected by
calcium chloride drying tubes. A suspension of
58 g. (1.07 moles) of sodium methoxide (Note 2) and
(Note 3) in
330 ml. of anhydrous ether (Note 4) is added, and stirring is begun. To the stirred suspension is added dropwise a solution of
133 g. (1 mole) of 2-chlorocyclohexanone2 (Note 5) and
(Note 6) diluted with
30 ml. of dry ether. The exothermic reaction is regulated by the rate of addition of the chloroketone; about 40 minutes is required for the addition. After the addition of the chloroketone is complete, the mixture is stirred and heated under reflux for 2 hours
(Note 7) and is then cooled. Water is added until the salts are dissolved
(Note 8). The
ether layer is separated, and the aqueous layer is saturated with
sodium chloride. After extraction of the aqueous layer two
50-ml. portions of ether, the ethereal solutions are combined and washed successively with
100-ml. portions of 5% hydrochloric acid,
5% aqueous sodium bicarbonate solution, and saturated
sodium chloride solution. The
ether solution is dried over
magnesium sulfate, and the
magnesium sulfate is removed by filtration and washed with
ether. Removal of the
ether by distillation at atmospheric pressure leaves the crude ester, which is distilled, with fractionation
(Note 9), at 70–73°/48 mm.,
n25D 1.4341. The yield of
methyl cyclopentanecarboxylate is
72–78 g. (
56–61%)
(Note 10).
2. Notes
1.
A
mercury seal and a Hershberg stirrer made from tantalum wire are suitable.
2.
Commercial (Matheson Co., Inc.) sodium methoxide is most convenient. The reaction can be run using
sodium methoxide prepared from
sodium and
methanol, but this procedure is more tedious since it requires the removal of a considerable amount of
methanol.
3.
A slight excess of
sodium methoxide should always be used. When an equivalent amount is employed, slightly lower yields are obtained.
4.
Commercial anhydrous analytical reagent
ether, from sealed cans, was employed by the checkers without further drying.
5.
The
2-chlorocyclohexanone2 employed by the checkers had b.p.
98–99°/14.5 mm.,
n25D 1.4826. Purity is critical in determining the yield of
methyl cyclopentanecarboxylate.
6.
Chlorocyclohexanone is added to the
sodium methoxide, since the reverse mode of addition results in lower yields through increased formation of high-boiling condensation products.
7.
The submitters report that equivalent yields are obtained when the mixture is allowed to stand overnight after the addition of the chloroketone is complete.
8.
The checkers found that approximately 175 ml. of water is required.
9.
The checkers employed a
Podbielniak column,
0.8 × 125 cm., with tantalum wire spiral and partial reflux head.
310.
The residue of higher-boiling material arises from the condensation of both the starting material and the product under the influence of
sodium methoxide.
3. Discussion
Methyl cyclopentanecarboxylate has been prepared by the Favorskii rearrangement of
2-chlorocyclohexanone with
sodium methoxide.
4 Other alkyl esters of cyclopentanecarboxylic acid have been prepared by employing the corresponding alkoxides with
2-chlorocyclohexanone.
4,5,6 The Favorskii reaction has been reviewed elsewhere.
7
The methyl ester has also been obtained by esterification of
cyclopentanecarboxylic acid.
8 The acid in turn, has been prepared by the Favorskii rearrangement,
6,7,9,10,11 by the reaction of cyclopentyl Grignard reagent with
carbon dioxide,
12 by the carbonylation of
cyclopentyl alcohol with
nickel carbonyl13 or with
formic acid in the presence of
sulfuric acid,
14 by the hydrogenation of
cyclopentene-1-carboxylic acid prepared from ethyl cyclopentanone-2-carboxylate15 or from
cyclopentanone cyanohydrin,
16 and from
cyclopentene and
carbon monoxide in the presence of
sulfuric acid.
17
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
sulfuric acid (7664-93-9)
hydrochloric acid (7647-01-0)
methanol (67-56-1)
ether (60-29-7)
carbon monoxide (630-08-0)
sodium bicarbonate (144-55-8)
sodium chloride (7647-14-5)
formic acid (64-18-6)
carbon dioxide (124-38-9)
sodium methoxide (124-41-4)
sodium (13966-32-0)
magnesium sulfate (7487-88-9)
ethyl cyclopentanone-2-carboxylate (611-10-9)
cyclopentyl alcohol (96-41-3)
Cyclopentene (142-29-0)
nickel carbonyl
2-Chlorocyclohexanone,
chlorocyclohexanone (822-87-7)
Methyl cyclopentanecarboxylate,
Cyclopentanecarboxylic acid, methyl ester (4630-80-2)
cyclopentanecarboxylic acid (3400-45-1)
cyclopentene-1-carboxylic acid
cyclopentanone cyanohydrin
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