Organic Syntheses, Coll. Vol. 6, p.43 (1988); Vol. 59, p.176 (1979).
A solution of 6 g. (0.044 mole) of adamantane (Note 1)
in 100 ml. of pentane
and 500 g. of silica gel (Note 2)
are placed in a 2-l., round-bottomed flask (Note 3)
. The pentane
is removed by rotary evaporation at room temperature under reduced pressure (20 mm.), and the resulting dry silica gel is allowed to rotate for an additional 2 hours (Note 4)
. The adamantane–silica gel dispersion is poured through a powder funnel into the ozonation vessel (Note 5)
, which is then immersed in a 2-propanol–dry ice bath
at −78°. A flow of oxygen
is passed through the vessel at a rate of 1 l. per minute for 2 hours, after which the internal temperature reaches −60 to −65° (Note 6)
. The ozone generator (Note 7)
is turned on, and the ozone
mixture is passed through the vessel for ca.
2 hours, causing the silica gel to become dark blue (Note 8)
and (Note 9)
. The cooling bath
is removed, and the vessel is allowed to warm to room temperature in the hood over a 3-hour period. The silica gel is transferred to a chromatography column, and the organic material is eluted with 3 l. of ethyl acetate
. Evaporation of the solvent affords 6.1–6.4 g.
of crude adamantanol (Note 10)
, which is dissolved in 200 ml. of 1:1 (v/v) dichloromethane–hexane
by heating on a steam bath
. The solution is filtered, concentrated to incipient crystallization and placed in a freezer at −20°. After a crop of fine, white needles (3.0–3.2 g.
), m.p. 280–282°
(sealed capillary), is collected, the mother liquor is concentrated and cooled to separate two additional crops, which give 2.2–2.6 g.
and have melting point ranges of 270–274° to 275–280°
(sealed capillary) (Note 11)
. The total yield of 1-adamantanol
is 5.4–5.6 g.
) (Note 12)
Adamantane is available from Aldrich Chemical Company, Inc., and Fluka AG, Buchs, Switzerland
Silica gel 60, with particle sizes ranging from 0.063 to 0.200 mm. (70–230 mesh), is suitable and may be purchased from Brinkmann Instruments, Inc., or E. Merck, Darmstadt, Germany. The submitters report that silica gel of this type normally contains ca.
5% water, which may be removed by drying at 300° for several hours, and that somewhat better yields are obtained when the silica gel is dried in this manner before use.
The submitters have found that the absorption of adamantane
on silica gel
may also be accomplished by mixing the dry solids in a closed flask for a few hours.
Heating should be avoided to prevent loss of some of the adamantane
The submitters have used both a tightly closed, 1-l. gas-washing bottle
and the apparatus shown in Figure 1
for ozonation vessels. They recommend that the glass joints not be greased. The apparatus used by the checkers consisted of a cylindrical, two-necked vessel
having dimensions given in Figure 1
. One neck of the vessel was fitted with a Claisen distillation head
and the other with a thermometer
with its bulb positioned in the middle of the vessel. A bent gas-dispersion tube with an extra-coarse sintered-glass frit extending through the vertical branch of the Claisen head
to within 2–3 mm. of the center of the bottom of the flask served as the gas inlet. The curved branch of the Claisen head was fitted with a drying tube and this functioned as the gas exit.
The checkers found that the maintenance of a flow of oxygen
during the cooling period prevented clogging of the glass frit and a building up of pressure in the gas-inlet tube in their apparatus.
A Welsbach T-816 Ozonator
purchased from the Welsbach Corporation, Philadelphia, Pennsylvania, was used. The oxygen
stream was dried by passage through dry silica gel and molecular sieves and introduced into the ozonator with the operating voltage set at 115 V., the gas pressure at 8 p.s.i.g., and the gas flow rate at 1 l. per minute. The resulting ozone
flow rate was 0.00245 mole per minute, as determined by titration of a potassium iodide trap
. Org. Synth., Coll. Vol. 5, 489 (1973)
In the apparatus used by the checkers, the internal temperature was between −45° and −65° while ozone
was being passed through the silica gel
. The use of lower bath temperatures results in the adsorption of a greater quantity of ozone
on the silica gel; consequently, shorter reaction times and higher conversions were realized. However, since ozone liquifies at
−112°, there is a serious danger of explosion.
flow is stopped when the silica gel reaches a constant, dark blue color. The time required for saturating the silica gel with ozone
depends on the type of silica gel used and on whether it has been dried (Note 2)
A GC analysis on the crude adamantanol
was carried out by the checkers using a 1.8 m. × 3 mm. column packed with 5% silicone oil (SE-30) supported on Chromosorb W
and the following column temperature program: hold at 120° for 6 minutes and then increase at ca.
8° per minute. The chromatogram of the product from one run showed a major peak at retention time of 10 minutes and three minor peaks with retention times of 11.2, 12, and 13.7 minutes and relative areas amounting to 1.5, 1.6, and 4% of the major peak, respectively. A GC analysis by the submitters with 5% diethylene glycol succinate
supported on Chromosorb W as a stationary phase at 110–160° showed peaks for adamantan-1,3-diol
, as by-products totaling 7%, in addition to the peak for 1-adamantanol
A GC analysis by the checkers (see (Note 10)
) on the material in the third crop from one run showed a major peak for 1-adamantanol
and a second minor peak having an area ca.
12% of that of the major peak. In another run the area of the peak from this by-product in the third crop was less than 2% relative to that of 1-adamantanol
A yield of 5.8 g.
), m.p. 280–282°
, was obtained by the submitters. The IR, 1
H NMR, 13
C NMR, and mass spectra of the product were identical to those of an authentic sample of 1-adamantanol
. A mixed melting point with an authentic sample of 1-adamantanol
showed no depression.
The spectral characteristics of the product are as follows: IR (KBr) cm.−1 3350(OH), 1455, 1352, 1302, 1118, 1088; 1H NMR (CDCl3), δ (multiplicity, number of protons, assignment): 1.53 (s, 1H, OH), 1.55–1.80 (m, 12H, 6 CH2), 2.17 (broad s, 3H, 3CH); 13C NMR (CDCl3), δ (assignment): 30.7 (3CH), 36.1 (3CH), 36.1 (3CH2), 45.4 (3CH2), 68.2 (COH).
This "dry ozonation" procedure is a general method for hydroxylation of tertiary carbon atoms in saturated compounds (Table I).3,4,5,6
The substitution reaction occurs predominantly with retention of configuration. Thus, cis-decalin
, whereas cis- and trans-1,4-dimethylcyclohexane
afford cis- and trans-1,4-dimethylcyclohexanol
, respectively. The amount of epimeric alcohol formed in these ozonation reactions is usually less than 1%. The tertiary alcohols may be further oxidized to diols by repeating the ozonation; however, the yields in these reactions are poorer. For instance, 1-adamantanol
is oxidized to 1,3-adamantanediol
yield. Secondary alcohols are converted to the corresponding ketone. This method has been employed for the hydroxylation of tertiary positions in saturated acetates and bromides.
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