Org. Synth. 1977, 56, 25
DOI: 10.15227/orgsyn.056.0025
ALLYLIC OXIDATION WITH HYDROGEN PEROXIDE–SELENIUM DIOXIDE: trans-PINOCARVEOL
[Bicyclo[3.1.1]heptan-3-ol, 6,6-dimethyl-2-methylene-, (1α,3α,5α)-]
Submitted by J. M. Coxon, E. Dansted, and M. P. Hartshorn
1.
Checked by D. W. Brooks and S. Masamune.
1. Procedure
Caution! Selenium compounds are exceedingly toxic (Note 1). Hydrogen peroxide attacks the skin and may decompose violently (Note 2). The reaction should be carried out behind a safety screen and in an efficient fume hood, and the operator should wear safety glasses and rubber gloves.
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 500-ml., three-necked, round-bottomed flask is fitted with a mechanical stirrer, a thermometer, a dropping funnel, and a reflux condenser. A solution of 0.74 g. (0.0067 mole) of selenium dioxide in 150 ml. of tert-butyl alcohol is introduced into the flask, followed by 68 g. (0.50 mole) of β-pinene (Note 3). The resulting mixture is warmed to 40° with a hot water bath before 35 ml. (0.62 mole) of 50% aqueous hydrogen peroxide (Note 2) is added dropwise over 90 minutes, during which time the mixture is maintained at 40–50° by occasional immersion in a cold water bath. After stirring for an additional 2 hours, the reaction mixture is diluted with 50 ml. of benzene, washed with three 50-ml. portions of saturated aqueous ammonium sulfate, and dried over sodium sulfate. A small amount of hydroquinone is added (Note 4), and the solvents are removed on a rotary evaporator. trans-Pinocarveol is isolated by simple distillation under reduced pressure, yielding 37–42 g. (49–55%), b.p. 60–70° (1 mm.), n22D 1.4972, [α]20D + 53.5 to + 60.0° (c 2.5, methanol) (Note 5).
2. Notes
1.
The physiological properties of selenium compounds are similar to those of arsenic compounds. Any
selenium dioxide solid or solution spilled on the skin should be removed immediately by washing under running water.
2.
Aqueous
50% hydrogen peroxide causes immediate blistering if allowed to come into contact with the skin. The presence of metal salts may cause decomposition of the
hydrogen peroxide.
3.
The checkers purchased
β-pinene, [α]20D − 16.6° (c 1.9, methanol), from Aldrich Chemical Company, Inc.4.
Hydroquinone stabilizes the product during distillation by reducing traces of peroxide present in the reaction product.
5.
GC analysis (capillary column coated with polypropylene glycol, 60.9 m., 100°) indicated that the product was
ca. 95% pure (submitters). The checkers found the once-distilled material to be analytically pure. Analysis calculated for C
10H
16O: C, 78.90; H, 10.59. Found: C, 78.71; H, 10.55. IR (CCl
4) cm.
−1: 3600 medium, 3460 broad, medium, 1645 medium;
1H NMR (CCl
4), δ (multiplicity, coupling constant
J in Hz., number of protons): 0.63 (s, 3H), 1.26 (s, 3H), 1.6–2.5 (m, 6H), 2.88 (s, 1H, O
H), 4.33 (approx. d,
J = 7, 1H), 4.74 (approx. s, 1H), 4.96 (approx. s, 1H).
3. Discussion
trans-Pinocarveol is an important intermediate in the preparation of substituted pinane systems. It has been prepared by oxidation of
β-pinene with
lead tetraäcetate and hydrolysis of the corresponding ester (
32%);
2 by photosensitized oxidation of
α-pinene, followed by reduction of the corresponding hydroperoxide (
35%);
3 by oxidation of
β-pinene with molar quantities of
selenium dioxide (
53–64%);
4 and by epoxidation of
α-pinene followed by isomerization with a variety of bases, of which
lithium diethylamide (
74–80% yield over the two steps) is best.
5
The present procedure is a convenient, one-step method of preparing optically active trans-pinocarveol. Although lower in yield than the lithium diethylamide procedure, it is more readily adaptable to large-scale work. Moreover, the two methods are complimentary in the conditions required (neutral vs. basic) and in the overall transformation accomplished:
Since only catalytic quantities of selenium dioxide are required, the danger of handling large quantities of this material (Note 1) is avoided. Furthermore, the problems associated with the formation of selenium and organoselenides, which commonly arise in oxidations using molar quantities of selenium dioxide, are not encountered.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
trans-Pinocarveol
Benzene (71-43-2)
methanol (67-56-1)
hydroquinone (123-31-9)
sodium sulfate (7757-82-6)
selenium dioxide (7446-08-4)
hydrogen peroxide (7722-84-1)
ammonium sulfate (7783-20-2)
selenium
tert-butyl alcohol (75-65-0)
lithium diethylamide
Bicyclo[3.1.1]heptan-3-ol, 6,6-dimethyl-2-methylene-, (1α,3α,5α)-
α-pinene (7785-70-8)
β-pinene (18172-67-3)
lead tetraacetate (546-67-8)
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