New syntheses of 1,1-dichloro-2,2,2-trifluoroethyl isocyanate and its reaction with triethyl phosphite [2]

Full text of DOI:10.1023/A:1020816905116

Russian Journal of General Chemistry, Vol. 72, No. 8, 2002, pp. 1313 1314. Translated from Zhurnal Obshchei Khimii, Vol. 72, No. 8, 2002,
pp. 1398 1399.
Original Russian Text Copyright
2002 by Boiko, Onikiichuk, Yakovenko, Kal’chenko.
LETTERS
TO THE EDITOR
New Syntheses of 1,1-Dichloro-2,2,2-trifluoroethyl Isocyanate
and Its Reaction with Triethyl Phosphite
V. I. Boiko, L. N. Onikiichuk, A. V. Yakovenko, and V. I. Kal’chenko
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received July 22, 2001
1
,1-Dichloro-2,2,2-trifluoroethyl isocyanate (I) and
O Cl
P
its derivatives are widely used for preparing of various
trifluoro-substituted heterocycles [1 3]. The existing
method of synthesis of isocyanate I by chlorination of
N-trifluoroacetylcarbamate with phosphorus penta-
chloride at 170 C gives no more than 34% of the
target product. Its purification is complicated [4].
(
EtO)3P
I
EtO
NCO
OEt CF3
III
a
EtO OEt
P=O
O
P
b
EtO
EtO
2
(EtO)3P
(EtO)3P
NCO
We have developed a new method for preparing
,1-dichloro-2,2,2-trifluoroethyl isocyanate (I) in 85%
yield, based on the reaction of the available trifluoro-
acetyl isocyanate (II) with phosphorus pentachloride
in toluene.
1
CF3
IV
spectrum. Each group shifts the signal of the trifluoro-
methyl group by about 10 ppm downfield as com-
pared to the starting isocyanate.
O
Cl
+
PCl5
F3C
NCO
F3C
POCl3
NCO
Cl
1
,1-Dichloro-2,2,2-trifluoroethyl isocyanate (I).
II
I
A mixture of 41.7 g of trifluoroacetyl isocyanate (II),
93.7 g of phosphorus pentachloride, and 75 ml of to-
luene were heated for 50 h. The temperature of the
reaction mixture was gradually increased to keep the
mixture boiling. Isocyanate I was isolates by fractional
distillation. Repeated distillation gave 47.1 g (85%)
Compound I contains labile chlorine atoms and is
a convenient synthon for preparing -phosphorylated
alkyl isocyanates. One of the main methods of such
phosphorylation is the Arbuzov reaction. The Arbuzov
reactions with 1,1-dihaloalkyl isocyanates were pre-
viously used to prepare both mono- and diphosphoryla- of compound I, bp 65 66 C {published data [4]: bp
1
ted derivatives [8], but the yields, as a rule, were not
high, and individual products could not always be
isolated.
65 C). IR spectrum (CCl ), , cm : 2290 (N=C=O).
4
1
9
F NMR spectrum (acetone-d6), F, ppm: 83.0 s
(CF3).
It occured that isocyanate I easily reacts with tri-
ethyl phosphite. Depending on the reagent ratio, 1-
chloro-1-(diethoxyphosphinoyl)-2,2,2-trifluoroethyl
isocyanate (III) or 1,1-bis(diethoxyphosphinoyl)-2,2,2-
trifluoroethyl isocyanate are formed. Monophos-
phorylation takes place in boiling benzene, and di-
phosphorylation, in toluene.
1
-Chloro-2,2,2-trifluoro-1-(diethoxyphosphino-
yl)ethyl isocyanate (III). a. A solution of 0.02 mol of
triethyl phosphite in 5 ml of benzene was added to a
solution of 0.02 mol of isocyanate I in 15 ml of
benzene. After heat evolution had ceased, the reaction
mixture was boiled for 2 h until ethyl chloride no
longer evolved. The benzene was removed at reduced
pressure, and the residue was distilled in a vacuum to
obtain 79% of isocyanate III, bp 94 95 C (10 mm),
Isocyanates III and IV are colorless liquids which
can be distilled in a vacuum. The IR spectra of these
2
D
0
1
substances contain strong N=C=O absorption bands at
n
1.4103. IR spectrum (CCl ), , cm : 2258
4
1
1
2
260 cm . Note a strong effect of the phosphoryl
(N=C=O). H NMR spectrum (acetone-d ), , ppm:
1.34 t (6H, CH ), 4.34 m (4H, CH ). F NMR spec-
6
1
9
19
group on the positions of signals in the F NMR
3
2
1
070-3632/02/7208-1313$27.00 2002 MAIK Nauka/Interperiodica

1314
BOIKO et al.
trum (acetone-d6), , ppm: 75.5 s (CF ). Found, %:
All the reactions were carried out in anhydrous sol-
vents in moisture-proof conditions. The IR spectra
F
3
P 10.46. C H ClF NO P. Calculated, %: P 10.48.
7
10
3
4
1
were recorded on a UR-20 spectrometer. The H
1
,1-Bis(diethoxyphosphinoyl)-2,2,2-trifluoro-
19
(
internal reference HMDS), F (internal reference
ethyl isocyanate. a. A solution of 0.04 mol of triethyl
phosphite in 10 ml of toluene was added to a solution
of 0.02 mol of isocyanate I in 15 ml of toluene. Af-
ter heat evolution had ceased, the reaction mixture
was heated under reflux for 2 h until ethyl chloride
no longer evolved. The toluene was removed, and the
residue was fractionated to obtain 53% of isocyanate
31
CCl F), and P NMR spectra (external reference
3
H PO ) were obtained on a Varian VXR-300 spec-
3
4
trometer at 299.95, 282.20, and 121.42 MHz, res-
pectively.
REFERENCES
2
0
1. Vovk, M.V., Dorokhov, V.I., Boiko, V.I., and Sama-
ray, L.I., Khim. Geterotsikl. Soedin., 1993, no. 11,
pp. 1472 1475.
IV, bp 111 C (0.03 mm), n 1.4232. IR spectrum
D
1
1
(
(
CCl ), , cm : 2261 (N=C=O). H NMR spectrum
4
CDCl ), , ppm: 1.32 t, 1.33 t (12H, diastereotopic
CH groups), 4.27 m (8H, CH ). F NMR spectrum
acetone-d6), F, ppm: 66.1 s (CF3). P NMR spec-
trum (CDCl3), P, ppm: 9.34 s. Found, %: C 32.97, H
3
1
9
2. Uneyama, K., Yamashita, F., Sugimoto, K., and Mori-
moto, O., Tetrahedron Lett., 1990, vol. 31, no. 19,
pp. 2717 2718.
3
3
3
1
(
5
3
.11, P 15.82. C H F NO P . Calculated, %: C
3.26, H 5.06, P 15.60. Together with target product
3. Vovk, M.V., Boiko, B.I., and Samaray, L.I., Ukr. Khim.
Zh., 1993, vol. 59, no. 10, pp. 1081 1082.
1
1
29
3
7 3
IV, tetraethyl pyrophosphate was isolated in 25%
yield, bp 39 40 C (0.03 mm), n 1.4071.
4
. Boiko, V.I., Gertsyuk, M.N., and Samaray, L.I., Zh.
Org. Khim., 1988, vol. 24, no. 2, pp. 451 452.
2
0
D
b. A solution of 0.02 mol of triethyl phosphite in
0 ml of toluene was added to a solution of 0.02 mol
5. Boiko, V.I. and Samaray, L.I., Ukr. Khim. Zh., 1992,
1
vol. 58, no. 9, pp. 797 798.
of isocyanate I in 15 ml of toluene. The resulting
mixture was heated under reflux for 2 h until ethyl
chloride no longer evolved. The toluene was removed
at reduced pressure, and the residue was distilled in a
vacuum to obtain 54% of isocyanate IV. The sub-
stance is identical to that prepared by procedure a.
Yield of tetraethyl pyrophosphate 27%.
6
7
. Boiko, V.I. and Samaray, L.I., Ukr. Khim. Zh., 1995,
vol. 61, no. 8, pp. 110 112.
. Kiemstedt, W. and Sundermeyer, W., Chem. Ber., 1982,
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8. Kozhushko, B.N., Lomakina, A.V., and Shokol, V.A.,
Usp. Khim., 1989, vol. 58, no. 11, pp. 1869 1895.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 8 2002