Organic Syntheses, CV 5, 877
Submitted by Nikolaus Fischer
1 and G. Opitz
2.
Checked by Hermann Ertl, Ian D. Rae, and Peter Yates.
1. Procedure
Caution!
Diazomethane is both explosive and poisonous, and all operations involving its preparation and use must be carried out in a
hood. Follow the directions for its handling given in earlier volumes.
3,4
In a
500-ml. three-necked flask equipped with a
mechanical stirrer, a
dropping funnel, and a
reflux condenser fitted with a
potassium hydroxide drying tube are placed
7.0 g. (0.069 mole) of triethylamine (Note
1) and a solution of
3.15 g. (0.075 mole) of diazomethane in 200 ml. of ether (Note
2). The flask is cooled in an
ice bath, and a solution of
13.0 g. (0.052 mole) of D-camphor-10-sulfonyl chloride (Note
3) in
75 ml. of anhydrous ether is added dropwise over a period of 1 hour.
Triethylamine hydrochloride slowly precipitates. The reaction mixture is stirred for an additional 30 minutes and then concentrated to
ca. 150 ml. under reduced pressure (
water aspirator) with continued stirring to remove the excess of
diazomethane. The mixture is filtered under reduced pressure; the precipitate is washed with
50 ml. of anhydrous ether, giving
6.7 g. (
94%) of
triethylamine hydrochloride. The combined filtrate and washings are freed of solvent on a
rotary evaporator at room temperature to give
10.7 g. (
90%) of crude
episulfone, m.p.
76–85° (dec.) (Note
4). This is used without purification in the next step; it can be purified by crystallization from a little
methanol at −20°. This gives colorless episulfone, m.p.
83–85° (dec.),
[α]24D −6.72° (
methanol,
c = 3.20); infrared bands at 3070, 1300, and 1170 cm.
−1 (Note
5).
The crude
episulfone (3.0 g.) is placed in a
10-ml. round-bottomed flask fitted with a reflux condenser and is heated at 95° for 30 minutes, when it decomposes with loss of
sulfur dioxide. The reflux condenser is replaced with a distillation head (Note
6), and the yellow residue is distilled under reduced pressure (water aspirator).
D-2-Oxo-7,7-dimethyl-1-vinylbicyclo[2.2.2]heptane (
1.7 g.,
71% based on sulfonyl chloride), b.p.
95–96° (10 mm.), distills at a bath temperature of 110–120°. Sublimation at 60° (0.01 mm.) gives the olefin as colorless, waxy crystals, m.p.
64–65°,
[α]25D +16.35° (
methanol,
c = 2.16); infrared band at 1650 cm.
−1.
2. Notes
4. The checkers obtained higher yields (
94–97%) of less pure material [m.p.
50–78° (dec.)].
5. The checkers observed that the
episulfone decomposed slowly at room temperature and, on one occasion, during evaporation at 15°.
6. The checkers found it advisable to use an apparatus with a wide-bore side arm (18 mm.) without a condenser.
3. Discussion
4. Merits of the Preparation
The method is of general applicability
8,9 for the synthesis of olefins. Other sulfonyl chlorides, RCH
2SO
2Cl, have been used where R = H, C
2H
5, C
6H
5, and C
6H
5CH
2; other diazoalkanes that have been used are
diazoethane and
1-diazo-2-methyl-propane. In all cases the olefins form without double-bond migration. A review
9 of the method is available.
This preparation is referenced from:
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