Org. Synth. 1962, 42, 8
Submitted by Paul von R. Schleyer, M. M. Donaldson, R. D. Nicholas, and C. Cupas1
Checked by William G. Dauben and Fred G. Willey.
. A solution of 200 g. (1.51 moles) of purified dicyclopentadiene (Note 1)
in 100 ml. of dry ether
containing 1.0 g. of platinum oxide
is hydrogenated at 50 p.s.i. hydrogen
pressure using a Parr apparatus. The reaction mixture becomes quite warm during the initial stage of the hydrogenation,2
and the uptake of 2 mole equivalents of hydrogen
requires 4–6 hours. The catalyst is removed by suction filtration, and the filtrate is distilled at atmospheric pressure through a 30-cm. Vigreux column
When the removal of the ether is complete, the condenser at the top of the column is replaced by a wide-diameter adapter the bottom of which is placed in a receiver flask immersed in an ice bath. The adapter is heated (Note 2) to prevent premature solidification of the distillate. The distillation is continued and the endo-tetrahydrodicyclopentadiene, b.p. 191–193°, is collected. The yield is 196–200 g. (96.5–98.4%). The melting point depends on the purity of the starting material but generally is above 65°.
B. Adamantane. In a 500-ml. Erlenmeyer flask having a 24/40 standard taper joint are placed 200 g. (1.47 moles) of molten endo-tetrahydrodicyclopentadiene and a magnetic stirring bar. A well-greased inner joint (2.2 × 15 cm., 24/40) is fitted into the top of the flask to serve as an air condenser, and 40 g. of anhydrous aluminum chloride is added through the opening (Note 3). The reaction mixture is simultaneously stirred and heated at 150–180° (Note 4), (Note 5) by means of a combination magnetic stirrer-hot plate. Aluminum chloride sublimes to the top of the flask, especially at the beginning of the reaction, and the accumulated sublimate is, from time to time, pushed down into the reaction liquid. After the mixture has been heated for 8–12 hours, the flask is removed from the hot plate-stirrer and the black contents upon cooling separate into two layers. The upper layer, a brown mush of adamantane and other products, is decanted carefully from the lower black tarry layer into a 600-ml. beaker. The Erlenmeyer flask is rinsed five times with a total of 250 ml. of petroleum ether (b.p. 30–60°) with decantation into the same beaker (Note 6), (Note 7). The petroleum ether suspension is warmed until all the adamantane is in solution; there should be an appreciable excess of solvent. The solution is decolorized by careful addition of 10 g. of chromatography-grade alumina, the hot solution filtered, and the alumina and the beaker washed thoroughly with solvent. The nearly colorless filtrate (Note 8) is concentrated to a volume of about 200 ml. by distillation and then cooled in a Dry Ice-acetone bath. The solid adamantane is removed by suction filtration and there results 27–30 g. (13.5–15.0%) of crystals, melting point about 255–260° (Note 9), (Note 10). One recrystallization from petroleum ether raises the melting point to 268–270° (Note 11), (Note 12).
Technical grade dicyclopentadiene
is purified by distillation at water pump
pressure through a 30-cm. Vigreux column, and the fraction boiling at 64–65°/14 mm.
) is used in the reaction. The best material is solid or semisolid at room temperature.
The adapter can readily be heated by placing an infrared lamp
The evolution of heat initially observed is due to the exothermic rearrangement of endo-tetrahydrodicyclopentadiene
to its exo
The temperature of the reaction is followed by inserting a thermometer
into the reaction flask through the joint.
Other methods of heating and stirring may be used but are more troublesome because of the tendency of aluminum chloride
to sublime and clog top-mounted stirrers.
If appreciable amounts of tar have been transferred to the beaker, repeat the decantation and washing process into a clean beaker.
The tarry flasks and beakers can be cleaned easily with acetone
. Do not use water
until all the tar has been removed.
If necessary, the filtrate should be warmed to dissolve all the adamantane
The melting point must be taken in a sealed capillary, and the sealed portion must be completely immersed in the liquid of the melting-point bath.
, 2–6 g.
, can be obtained by distilling the mother liquors through a 10-cm. Vigreux column
and chilling the fraction boiling between 180° and 200°. The filtrate from the collection of the second portion of adamantane
consists mostly of exo-tetrahydrodicyclopentadiene
The amount of this fraction, 30–100 g., depends on the severity of the rearrangement conditions. Much non-distillable residue is obtained. Conversion of the 180–200° fractions to adamantane
is brought about by treating them with aluminum chloride
as before, and the yields are comparable.
The recrystallization is not necessary unless material of the highest purity is desired.
can be prepared by analogous isomerizations.4
can be isolated from petroleum, where it is found in minute yield.5
Two multistep syntheses starting with tetraethylbicyclo[3.3.1]nonane-2,6-dione-1,3,5,7-tetracarboxylate
have been reported.6
Also, starting with endo-tetrahydrodicyclopentadiene
, it has been found that a catalyst composed of aluminum chloride
and hydrogen chloride
will bring about the rearrangement to adamantane
yield, but the reaction must be performed in a hydrogen
atmosphere at high pressure.7
A recent patent describes the conversion in up to 30%
yield using a boron trifluoride-hydrogen fluoride
catalyst under pressure.8
The present method is based on the published procedure of the submitters and is the preferred method by virtue of the greater convenience.4
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
hydrogen chloride (7647-01-0)
hydrogen fluoride (7664-39-3)
aluminum chloride (3495-54-3)
boron trifluoride (7637-07-2)
Tricyclo[126.96.36.199,7] decane (281-23-2)
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