Organic Syntheses, CV 5, 387
Submitted by A. J. Speziale and R. C. Freeman
1.
Checked by B. C. McKusick and H. D. Hartzler.
1. Procedure
A.
N,N-Diethyl-2,2,2-trichloroacetamide. A
1-l. three-necked flask equipped with a
stirrer and
dropping funnel is charged with
73 g. (1.00 mole) of diethylamine,
500 ml. of ether, and a solution of
40 g. (1.00 mole) of sodium hydroxide in 160 ml. of water. The mixture is stirred and maintained at a temperature of −10° to −15° by a
bath of Dry Ice and acetone while
200 g. (1.10 moles) of trichloroacetyl chloride is added in the course of 1 hour. The cooling bath is removed, the temperature is allowed to rise to 10°, and the organic layer is separated. The aqueous layer is extracted with two
50-ml. portions of ether. The
ether extracts are combined, washed with
50 ml. of 5% hydrochloric acid, two
50-ml. portions of 5% sodium bicarbonate solution, and 50 ml. of water, and dried over
magnesium sulfate. The
ether is removed by distillation at atmospheric pressure. The residue is distilled through a short indented Claisen still head at reduced pressure.
N,N-Diethyl-2,2,2-trichloroacetamide is collected at
77–79°/1.5 mm.;
nD25 1.4902–1.4912; weight
183–200 g. (
84–92%).
B.
N,N-Diethyl-1,2,2-trichlorovinylamine. The reaction is carried out in a
500-ml. three-necked flask equipped with an
efficient mechanical stirrer, a
thermometer, a
reflux condenser to which a
drying tube containing calcium chloride is attached, and a
250-ml. dropping funnel with a
pressure-equalizing tube. The flask is charged with
219 g. (2.00 moles) of N,N-diethyl-2,2,2-trichloroacetamide. A
gas-inlet tube is attached to the dropping funnel, and dry
nitrogen (Note
1) is passed through the apparatus for 5 minutes with stirring. The gas-inlet tube is removed briefly,
202 g. (2.00 moles) of tri-n-butylphosphine (Note
2) is placed in the dropping funnel, the gas-inlet tube is replaced, and
nitrogen is passed through the apparatus in a slow stream; the slow flow of
nitrogen is continued all during the reaction. The
phosphine is added at such a rate that a temperature of 85–90° is reached in 30 minutes (Note
3). The rate of addition is then slowed in order to maintain the temperature within this range. The total addition time is 45–55 minutes.
After all the
phosphine has been added, the
water bath is replaced by a heating mantle, and the reaction mixture is held at 85–95° for one additional hour and cooled to room temperature. The nitrogen-inlet tube, dropping funnel, and reflux condenser are removed, and the reaction flask is fitted with a
15 × 150-mm. Vigreux column for distillation under reduced pressure. The reaction mixture is then distilled (Note
4). The pot temperature rises from 94° to 150° during the distillation, and the crude
N,N-diethyl-1,2,2-trichlorovinylamine, weight
151–164 g., is collected at
73–120°/8–11 mm. Redistillation of the crude vinylamine through a
20 × 400-mm. column packed with glass helices affords
140–150 g. (
69–74%) of pure
N,N-diethyl-1,2,2-trichlorovinylamine, b.p.
78–79°/18 mm.,
nD25 1.4857–1.4867 (Note
5) and (Note
6).
2. Notes
2.
Tri-n-butylphosphine obtainable from Westvaco Mineral Products, 161 East Forty-second St., New York City, can be used without further purification.
3. Because this reaction is very exothermic, the
phosphine should be added cautiously.
4. The reaction and the initial distillation should be carried out on the same day.
6. If desired, the
tri-n-butylphosphine oxide can be recovered by continuing the distillation. Crude
tri-n-butylphosphine oxide distils at
115–118°/1–2 mm. (pot temperature 125–135°). The pure
phosphine oxide2 distils at
94–95°/0.03 mm.; m.p.
64.6–66.6°; yield
135–159 g. (
62–73%).
Caution! The reaction mixture should not be distilled to dryness. There should be a residue of about 40–50 ml.
3. Discussion
4. Merits of Procedure
The procedure has also been applied to the synthesis of
N,N-dimethyl-1,2,2-trichlorovinylamine from
trichloroacetamide (
60% yield),
3 and it probably is a general means of preparing N,N-dialkyl-1,2,2-trichlorovinylamines. The reaction is an unusual one involving reduction of the amide and halogen migration and is of theoretical interest.
Appendix
Compounds Referenced (Chemical Abstracts Registry Number)
hydrochloric acid (7647-01-0)
ether (60-29-7)
aniline (62-53-3)
sodium hydroxide (1310-73-2)
sodium bicarbonate (144-55-8)
oxygen (7782-44-7)
nitrogen (7727-37-9)
diethylamine (109-89-7)
magnesium sulfate (7487-88-9)
trichloroacetamide (594-65-0)
phosphine (7723-14-0)
triisopropyl phosphite (116-17-6)
Triethyl phosphite (122-52-1)
triphenylphosphine (603-35-0)
phosphine oxide
N,N-Diethyl-1,2,2-trichlorovinylamine,
Vinylamine, 1,2,2-trichloro-N,N-diethyl- (686-10-2)
trichloroacetyl chloride (76-02-8)
N,N-Diethyl-2,2,2-trichloroacetamide
vinylamine (593-67-9)
N,N-dimethyl-1,2,2-trichlorovinylamine
trimethyl phosphite (121-45-9)
tri-n-butylphosphine (998-40-3)
tri-n-butylphosphine oxide (814-29-9)
N,N-diethyl-N'-phenyl-2,2-dichloroacetamidine
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