Org. Synth. 1953, 33, 88
DOI: 10.15227/orgsyn.033.0088
cis-STILBENE
Submitted by Robert E. Buckles and Norris G. Wheeler
1.
Checked by T. L. Cairns and J. C. Lorenz.
1. Procedure
A
500-ml. three-necked flask is fitted with a
reflux condenser and a
thermometer, the bulb of which reaches far enough into the flask to be covered by the liquid. A solution of
46.0 g. (0.205 mole) of α-phenylcinnamic acid (p. 777) (Note 1) in
280 ml. (307 g., 2.38 moles) of quinoline (Note 2) is added to the flask along with
4.0 g. of copper chromite.
2 The reaction flask is heated by means of a mantle or an
oil bath until the temperature of the reaction mixture reaches 210–220°. The mixture is kept within this temperature range for 1.25 hours. The solution is then cooled immediately and added to
960 ml. of 10% hydrochloric acid in order to dissolve the
quinoline (Note 3). The product is extracted from this mixture with two
200-ml. portions of ether followed by a 100-ml. portion. The combined
ether extracts are filtered to remove particles of catalyst, washed with
200 ml. of 10% sodium carbonate, and dried over anhydrous
sodium sulfate. The dry solution is removed from the drying agent by filtration and heated on a
steam bath to distil the
ether. The residue is dissolved in a
hexane fraction, b.p.
60–72° (Skellysolve B); the solution is cooled to 0° and filtered to remove
trans-stilbene, if any. The hydrocarbon solvent is removed by distillation, and the
cis-stilbene is distilled. The yield is
23–24 g. (
62–65%), b.p.
133–136° /10 mm.,
95–97° /1 mm.;
n25D 1.6183–1.6193,
n20D 1.6212–1.6218
(Note 4).
2. Notes
1.
The isomer of
α-phenylcinnamic acid of m.p.
172–173° is used (
p. 777). The isomer of m.p.
137–139° yields
trans-stilbene on decarboxylation.
32.
Practical grade quinoline containing about 10% of isoquinoline and quinaldine can be used. If the
quinoline contains water, the desired temperature can be reached by distillation of a small amount of
quinoline directly from the reaction mixture.
3.
The
quinoline can be recovered by neutralization of the aqueous solution, extraction of the
quinoline into
ether, and distillation of the dried (over
barium oxide)
ether extract.
4.
The product obtained from this type of decarboxylation is reported to contain only about
5% of trans-stilbene.
4 A sample made according to the above directions can be treated with
bromine in
carbon tetrachloride at room temperature in the dark to give an 80–85% yield of the
dl-dibromide which arises from
trans addition to
cis-stilbene. The
meso-dibromide, which is very insoluble and easily separated, is obtained only to the extent of 10% or less. Part of the latter product may arise from the action of bromine atoms on
cis-stilbene rather than from
trans addition to
trans-stilbene. The
cis-stilbene prepared by this method is readily and completely soluble in cold
absolute ethanol. It freezes solid at about −5°. Its ultraviolet absorption coefficient (ε) is 1.10 × 10
4 at 274 mμ and 8.7 × 10
3 at 294 mμ, quite different from
trans-stilbene.
3. Discussion
cis-Stilbene has been prepared by the partial hydrogenation of
tolan;
5,6 by the electrolytic reduction of
tolan;
7 by the reduction of
tolan with a
copper-zinc couple;
8 by the reduction of the low-melting isomer of
α-bromostilbene with
zinc dust in 90% alcohol;
9 by the illumination of
trans-stilbene with ultraviolet light;
10 by the decarboxylation of the high-melting isomer of
α-phenylcinnamic acid in the presence of
barium hydroxide;
3 by heating
tolan with
diisobutylaluminum hydride11 or
zinc and acetic acid;
12 and by the reaction of
cis-bromostilbene with
butyllithium followed by treatment with
methanol.
13 The present method is based on that of Taylor and Crawford.
14
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
copper-zinc couple
ethanol (64-17-5)
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
methanol (67-56-1)
ether (60-29-7)
sodium carbonate (497-19-8)
bromine (7726-95-6)
sodium sulfate (7757-82-6)
barium oxide
carbon tetrachloride (56-23-5)
zinc (7440-66-6)
barium hydroxide (17194-00-2)
Quinoline (91-22-5)
COPPER CHROMITE
α-bromostilbene
quinaldine (91-63-4)
butyllithium (109-72-8)
hexane (110-54-3)
isoquinoline (119-65-3)
diisobutylaluminum hydride (1191-15-7)
α-Phenylcinnamic acid (3368-16-9)
trans-Stilbene (103-30-0)
cis-Stilbene (645-49-8)
cis-bromostilbene
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