Organic Syntheses, Coll. Vol. 5, p.315 (1973); Vol. 49, p.39 (1969).
A. N,N,N-Trimethylcyclooctylammonium iodide
. To a 2-l., three-necked, round-bottomed flask
equipped with a stirrer
, drying tube
, and pressure-equalizing dropping funnel are added 155.3 g. (1 mole) of N,N-dimethylcyclooctylamine (Note 1)
and 700 ml. of reagent grade methanol
. To the stirred solution is added 170.3 g. (1.2 moles) of iodomethane (Note 2)
dropwise over a 30-minute period. The flask is cooled intermittently with an ice bath
to keep the reaction temperature at approximately 25° (Note 3)
. After 1 hour the bath is removed and the reaction mixture is allowed to stir at 25° for an additional 3 hours.
The light yellow solution is transferred to a 2-l. round-bottomed flask, and the solvent is removed under reduced pressure (Note 4)
with slight warming. The solid product is triturated with 500 ml. of diethyl ether
, filtered, and washed with three 200-ml. portions of diethyl ether
. The white solid (291–296 g.
) is dried under reduced pressure, m.p. 269–270°
dec. (Note 5)
B. N,N,N-Trimethylcyclooctylammonium hydroxide
. To a 1-l. round-bottomed flask
equipped with a stirrer are added 100 g. (0.34 mole) of N,N,N-trimethylcyclooctylammonium iodide
, 76 g. of silver oxide (Note 6)
, and 350 ml. of distilled water. The suspension is stirred at room temperature for 5 hours and is filtered through a Buchner funnel
. The filter cake is washed with four 35-ml. portions of distilled water. The light yellow filtrate is transferred to a 1-l. round-bottomed flask and the volume is reduced to approximately 90 ml. employing a rotary evaporator
and a 40° water bath
. The viscous N,N,N-trimethylcyclooctylammonium hydroxide
solution is transferred (Note 7)
to a 200-ml. dropping funnel, with a pressure-equalizing side arm
, for use in the next step in the synthesis (Note 8)
. A 500-ml., three-necked, round-bottomed flask
is equipped with a nitrogen inlet capillary tube (Note 9)
, a short (10–20 cm.) unpacked column (Note 10)
, and a pressure-equalizing dropping funnel. The round-bottomed flask is connected by the unpacked column to a 100-ml. trap
cooled in an ice bath. This trap is then connected to a 200-ml. trap
cooled in dry ice-acetone (Note 11)
. The flask is heated in an oil bath
to 110–125°, and the apparatus is evacuated to a pressure of ca.
10 mm. under a constant sweep of nitrogen
. The hydroxide solution is added dropwise at approximately the rate of decomposition of the quaternary ammonium hydroxide (Note 12)
The combined distillates from the cold traps are allowed to come to room temperature (Note 13)
and are placed in a 1-l. separatory funnel
with 200 ml. of 5% hydrochloric acid
solution. The mixture of cis
- and trans
-cyclooctenes (Note 14)
is extracted with 200 ml. of n-pentane
and subsequently with two 50-ml. portions of n-pentane
. The n-pentane
extracts are combined and washed with 170 ml. of 5% sodium bicarbonate
To a 1-l. separatory funnel is added ca. 500 ml. of 20% aqueous silver nitrate solution (100 g. of Mallinckrodt C.P. crystals to ca. 500 ml. of water)
. The pentane
solution is added to the separatory funnel in five approximately equal portions, with intermittent shaking until all the silver nitrate
complex has gone into solution (Note 15)
It is convenient to use a rotary evaporator for removal of the solvents.
After one recrystallization from an acetone-methanol
mixture, the compound melts at 273–275°
dec. The compound is sufficiently pure for the next step in the synthesis without recrystallization.
Mallinckrodt purified silver oxide powder
was used. The reaction flask should be protected from direct sunlight with a suitable wrapping.
The flask may be rinsed with a minimum of water and transferred to the dropping funnel. The total volume of hydroxide solution at this point should not exceed 100 ml.
The conversion of the quaternary ammonium iodide to the hydroxide may also be carried out using a strongly basic ion exchange resin.4
The decomposition should be carried out under a constant sweep of nitrogen
. The nitrogen
may be introduced through the pressure-equalizing dropping funnel if that is more convenient.
The unpacked column should be wrapped with a heating tape, or Nichrome heating wire, and kept at ca.
110° throughout the decomposition.
The reaction is stopped and the trap, cooled in dry ice-acetone, is emptied when the reaction is ca.
one half finished to prevent plugging by ice. Most of the olefinic products are found in the first trap. The second trap contains mostly trimethylamine
About 3 hours is required to add the hydroxide solution. The rate of addition may be increased, but considerable foaming occurs during the decomposition, and caution should be taken that the hydroxide does not foam over into the traps.
This part of the experiment should be carried out in a hood
If the pentane
solution is added to the silver nitrate
solution too rapidly, the trans-cyclooctene
forms a dark precipitate that is difficult to get into solution. This situation can, however, be remedied by the addition of more silver nitrate
solution and continued shaking.
is removed and ca. 11 g.
is obtained on distillation, b.p. 65° (59 mm.)
Considerable foaming occurs during distillation of trans-cyclooctene
. The distillation may therefore be facilitated by use of a distilling adapter
with a foam trap. The distilling adapter (5225) may be purchased from Ace Glass Incorporated, Vineland, New Jersey. The bath temperature should be kept below 100° owing to the possibility of isomerization to cis
-olefin and polymerization.6
The distillation should be carried out as rapidly as possible because the condensed product evaporates under prolonged exposure to reduced pressure.
The submitters carried out this preparation on a 1.0-mole scale and obtained 49–51 g.
) of trans-cyclooctene
is stable for at least 1 year if kept under refrigeration and if a free radical inhibitor is used (e.g. di-t-butyl-resorcinol
). The compound has a very disagreeable odor.
This procedure illustrates a general method for preparing olefins by the elimination of an amine and a β-hydrogen atom.11
The present method is more convenient for adaptation to large-scale laboratory preparation than is the Wittig modification, which utilizes liquid ammonia
; both methods give essentially the same overall yield of trans-cyclooctene
The preparation of olefins via
is a stereo-specific elimination reaction which may be used to advantage when a mixture of cis
- and trans
-olefins is difficult to separate. However, all the reagents required to prepare the thiocarbonate are not readily available.
Chemical Abstracts Nomenclature (Collective Index Number);
hydrochloric acid (7647-01-0)
diethyl ether (60-29-7)
sodium bicarbonate (144-55-8)
silver oxide powder (20667-12-3)
silver nitrate (7761-88-8)
ammonium hydroxide (1336-21-6)
magnesium sulfate (7487-88-9)
dimethyl sulfoxide (67-68-5)
potassium t-butoxide (865-47-4)
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