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Org. Synth. 1959, 39, 70
DOI: 10.15227/orgsyn.039.0070
2,4,4-TRIMETHYLCYCLOPENTANONE
[Cyclopentanone, 2,4,4-trimethyl-]
Submitted by George D. Ryerson, Richard L. Wasson, and Herbert O. House1.
Checked by James Cason and Ralph J. Fessenden.
1. Procedure
In a 1-l. separatory funnel is placed a solution of 38.6 g. (0.25 mole) of isophorone oxide (Note 1) in 400 ml. of reagent grade benzene. To the solution is added 20 ml. (0.16 mole) of boron trifluoride etherate (Note 2). The resulting solution is mixed by swirling, allowed to stand for 30 minutes, then diluted with 100 ml. of ether and washed with 100 ml. of water (Note 3). The organic layer is shaken for 1–2 minutes with a solution of 40 g. (1.0 mole) of sodium hydroxide in 200 ml. of water (Note 4) and then washed with a second 100–ml. portion of water. The combined aqueous solutions are cooled briefly in running water and then extracted with two 50-ml. portions of ether. The ethereal extracts are added to the benzene-ether solution (Note 5), and the combined solution, after drying over anhydrous magnesium sulfate, is concentrated by distillation through a Claisen head. When the temperature of the distillate reaches about 80° (Note 6), the residual liquid is fractionally distilled (Note 7) under reduced pressure. The yield of 2,4,4-trimethylcyclopentanone, b.p. 61–62°/21 mm., nD28 1.4278–1.4288, is 17.7–19.8 g. (56–63%) (Note 8).
2. Notes
1. The preparation of isophorone oxide is described on p. 552
2. A practical grade of boron trifluoride etherate, purchased from Eastman Kodak Company, was redistilled before use. The pure etherate boils at 126°.
3. If the organic layer is dried over magnesium sulfate and fractionally distilled at this point, both 2,4,4-trimethylcyclopentanone and 2-formyl-2,4,4-trimethylcyclopentanone, b.p. 49–50° (2 mm.), nD25 1.4495, may be isolated. The pot residue from this distillation contains a small amount of the enol form of 3,5,5-trimethyl-1,2-cyclohexanedione which crystallizes from petroleum ether as white needles, m.p. 92–93°.
4. The specified period of shaking is sufficient to ensure complete deformylation of the intermediate β-ketoaldehyde. Ordinarily, no difficulty is experienced with emulsification provided that the recommended quantity (or more) of ether is added to the reaction mixture.
5. Acidification of the residual aqueous solution followed by extraction with ether permits the isolation of about 1 g. of the enol form of 3,5,5-trimethyl-1,2-cyclohexanedione (Note 3).
6. At this point about 150–200 ml. of liquid remains in the still pot. If the distillation is continued, the peppermint-like odor of the product, 2,4,4-trimethylcyclopentanone, can be detected in the distillate.
7. The submitters used a 24-cm. jacketed Vigreux column for this distillation. The checkers used a simple type of Podbielniak column, 50 cm. in length, with heated jacket and partial reflux head; after the last of the benzene had been distilled through the column, the following fractions were received:

Wt., g.

B.P./15 mm.

nD28


0.7

35–54°

1.4288

0.7

54–55°

1.4278

7.5

55°

1.4278

9.5

55°

1.4278

4.9

Residue, m.p. 80–90°


Thus a rather good sample of product may be obtained without use of fractionating equipment.
8. If an appreciable quantity of higher-boiling material (consisting of 2-formyl-2,4,4-trimethylcyclopentanone; (Note 4)) remains after the product has been collected, the residue should be dissolved in ether and shaken with aqueous sodium hydroxide as described in the procedure. After the ethereal extract has been dried over magnesium sulfate, distillation will permit the isolation of an additional quantity of 2,4,4-trimethylcyclopentanone.
3. Discussion
2,4,4-Trimethylcyclopentanone has been prepared by the oxidation of 1-hydroxy-2,4,4-trimethylcyclopentanecarboxylic acid with lead dioxide in sulfuric acid,2 by the hydrogenation of 2,4,4-trimethyl-2-cyclopentenone,3,4 by the Clemmensen reduction of dimethyldihydroresorcinol,5,6 by the distillation of powdered 2,4,4-trimethyladipic acid with sodium hydroxide,7 and by the saponification and decarboxylation of ethyl 2-keto-1,4,4-trimethylcyclopentanecarboxylate.8,9 The rearrangement of isophorone oxide10 appears to represent the optimum combination of favorable yield and convenient procedure.

References and Notes
  1. Massachusetts Institute of Technology, Cambridge, Massachusetts.
  2. Wallach, Ann., 414, 296 (1918).
  3. Fjader, Suomen Kemistilehti, 5, Suppl. 27 (1932) [Chem. Zentr., 1932 I, 3172].
  4. Nazarov and Bukhmutskaya, Bull. acad. sci. U.R.S.S., Classe sci. chim., 1947, 205 [C. A., 42, 7733 (1948)].
  5. Dey and Linstead, J. Chem. Soc., 1935, 1063.
  6. Auterinen, Suomen Kemistilehti, 10B, 22 (1937) [C. A., 32, 509 (1938)].
  7. Birch and Johnson, J. Chem. Soc., 1951, 1493.
  8. Qudrati-Khuda and Mukherji, J. Indian Chem. Soc., 23, 435 (1946).
  9. Chakravarti, J. Chem. Soc., 1947, 1028.
  10. House and Wasson, J. Am. Chem. Soc., 79, 1488 (1957).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

petroleum ether

β-ketoaldehyde

sulfuric acid (7664-93-9)

Benzene (71-43-2)

ether (60-29-7)

sodium hydroxide (1310-73-2)

magnesium sulfate (7487-88-9)

dimethyldihydroresorcinol

boron trifluoride etherate (109-63-7)

Isophorone oxide (10276-21-8)

2,4,4-Trimethylcyclopentanone,
Cyclopentanone, 2,4,4-trimethyl- (4694-12-6)

2-formyl-2,4,4-trimethylcyclopentanone

3,5,5-trimethyl-1,2-cyclohexanedione

1-hydroxy-2,4,4-trimethylcyclopentanecarboxylic acid

2,4,4-trimethyl-2-cyclopentenone

2,4,4-trimethyladipic acid

ethyl 2-keto-1,4,4-trimethylcyclopentanecarboxylate

lead dioxide