N-substituted N-phosphinotrifluoroactetamides in the staudinger reaction

Article abstract of DOI:10.1007/s11176-005-0431-7

Formerly unknown phosphazides with N-trifluoroacetamido groups at the phosphorus atom were obtained by the imination of N-(diphenylphosphino)-N- phenyltrifluoroacetamide with aryl azides. Stability of the phosphazides was found to depend on the nature of

Full text of DOI:10.1007/s11176-005-0431-7

Russian Journal of General Chemistry, Vol. 75, No. 9, 2005, pp. 1376 1378. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 9, 2005,
pp. 1448 1450.
Original Russian Text Copyright
2005 by Shalimov, Malenko, Repina, Sinitsa.
N-Substituted N-Phosphinotrifluoroactetamides
in the Staudinger Reaction
A. A. Shalimov, D. M. Malenko, L. A. Repina, and A. D. Sinitsa
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received July 15, 2004
Abstract Formerly unknown phosphazides with N-trifluoroacetamido groups at the phosphorus atom were
obtained by the imination of N-(diphenylphosphino)-N-phenyltrifluoroacetamide with aryl azides. Stability of
the phosphazides was found to depend on the nature of the radical at the amide nitrogen atom. The phos-
phazides were shown to readily eliminate nitrogen to yield phosphinimines that undergo the aza-Wittig
thermal rearrangement into N-phosphorylated trifluoroacetamidines.
A few examples of stable phosphazides obtained
by imination of P(III) derivatives with organic azides
are known [1]. The structure of some of them have
been proved by X-ray diffraction [2]. N-Arylphos-
phazides are stabilized by bulky and electron-acceptor
substituents in the azide phenyl ring, as well as bulky
and preferentially donor substituents on phosphorus.
Thus, the phosphazide obtained from picryl azide and
trimorpholino phosphite is so stable that it could not
be converted into corresponding phosphazo com-
pounds [3].
It was found that amidophosphines I slowly react
with azides II to give formerly unknown phospha-
zides III that have substituted N-trifluoroacetamido
groups on phosphorus. Compounds IIIa and IIIb are
the only phosphazides we could isolate individual as
yellowish amorphous materials. In the absence of
solvents, they can be stored for 7 10 days. Com-
pounds IIIc and IIId converted into corresponding
phosphinimides, gradually during reaction and fast on
heating. Phosphazides IIIa and IIIb eliminated nitro-
gen on heating to 40 50 C.
Proceeding with our research [4, 5] into the proper-
ties of N PIII-phosphorylated trihaloacetamides and
aiming at preparing formerly unknown types of phos-
phazides, we turned to reactions of N-methyl- and
N-phenyl-N-phosphinotrifluoroacetamides with aryl
azides.
Comparison of the properties of N-aryltriphenyl
phosphazides [6] and our prepared compounds shows
that replacement of even one phenyl group on phos-
phorus by the fairly bulky N-phenyl-N-trifluoroacet-
amide group renders phosphazides much more stable.
X2P=O
X2P
X2P=N N=NR
X2P=NR
CF3C N R
CF3C N R + R N3
CF3C N R
CF3C N R
N2
NR
O
O
O
Ia Ic
IIa IIc
IIIa IIId
IVa IVd
Va Vd
I, R = X = Ph (a); R = Me, X = Ph (b), OEt (c). II, R = Ph (a), p-FC6H4 (b), p-NO2C6H4 (c). III, R = X = Ph, R = Ph
(a), p-FC6H4 (b); R = Me, R = p-NO2C6H4, X = Ph (c), OEt (d). IV, R = Ph, R = X = Ph (a), R = p-FC6H4, X = Ph (b);
R = Me, R = p-NO2C6H4, X = Ph (c), OEt (d). V, R = X = Ph, R = Ph (a), p-FC6H4 (b); R = Me, R = p-NO2C6H4, X =
Ph (c), OEt (d).
Phosphinimines IV undergo the aza-Wittig rear-
rangement, partially during their synthesis and com-
pletely under reflux in toluene or xylene, to form
N-phosphorylated trifluoroacetamidines V (see [4]).
This conversion suggests that the electron-acceptor
iminophosphoryl and trifluoromethyl groups strongly
favor polarization of the carbonyl group.
EXPERIMENTAL
The IR spectra were obtained on a UR-20 spec-
1070-3632/05/7509-1376 2005 Pleiades Publishing, Inc.

N-SUBSTITUTED N-PHOSPHINOTRIFLUOROACTETAMIDES
1377
1
trophotometer. The H, 19F, and 31P NMR spectra
N-Phenyl-N-(triphenylphosphorimidoyl)triflu-
oroacetamide (IVa). Compound IIIa, 0.0056 mol,
was refluxed in 10 ml of benzene for 20 min. The
solvent was removed in a vacuum, and the residue
was washed with 20 ml of hexane. Yield 90%, mp
were taken on a Varian VXR-300 spectrometer at
299.15, 282.20, and 121.42 MHz, respectively,
against internal HMDS (1H, 13C) and CFCl3 (19F), and
external 85% H3PO4 (31P).
N PIII-Phosphorylated trifluoroacetamides I were
prepared according to [5].
1
116 117 C. IR spectrum (KBr), , cm : 1690 (C=O),
1
1340 1370 (P=N). H NMR spectrum (CDCl3),
,
ppm: 7.00 7.18 m (5H, Harom, NPh), 7.35 7.55 m
(10H, Harom, Ph2P), 7.84 7.93 m (5H, Harom, P=NPh).
19F NMR spectrum (benzene), F, ppm: 74.43. 31P
NMR spectrum (benzene), P, ppm: 16.20. Found, %:
N 6.10; P 6.59. C26H20F3N2OP. Calculated, %: N
6.03; P 6.67.
N-(Diphenylphosphino)-N-phenyltrifluoroacet-
amide (Ia). A solution of 0.0682 mol of chlorodi-
phenylphosphine in 20 ml of benzene was added to a
solution of 0.0686 mol of N-phenyl-N-(trimethylsilyl)-
trifluoroacetamide [7] in 30 ml of benzene. The reac-
tion mixture was kept for 3 h at 60 C. The solvent
was removed in a vacuum, and the residue was treated
at 5 to 10 C with hexane (2 30 ml). Yield 87%, mp
N-[N-(4-Fluorophenyl)diphenylphosphorimido-
yl]-N-phenyltrifluoroacetamide (IVb). A solution
of 0.0049 mol of compound IIIb in 10 ml of benzene
was refluxed for 20 min. The solvent was removed in
a vacuum, and the residue was washed with 20 ml of
hexane. Yield 86%, mp 106 107 C. IR spectrum
1
58 59 C. IR spectrum (Nujol), , cm : 1690 (C=O).
19F NMR spectrum (C6D6), F, ppm: 67.1 d (4JFP
16.7 Hz). 31P {1H} NMR spectrum (C6D6), P, ppm:
69.0 q (4JPF 16.7 Hz). Found P, %: 8.18. C20H15F3
NOP. Calculated P, %: 8.29.
1
1
(KBr), , cm : 1690 (C=O), 1340 1370 (P=N). H
NMR spectrum (CDCl3), , ppm: 6.98 7.20 m (5H,
Harom, NPh), 7.40 7.63 m (10H, Harom, Ph2P), 7.72 d
(2H, Harom), 7.80 d (2H, Harom, J 7.8 Hz). 19F NMR
spectrum (benzene), F, ppm: 75.02 (CF3), 122.52
(F). 31P NMR spectrum (benzene), P, ppm: 16.96.
Found, %: N 5.74; P 6.37. C26H19F4N2OP. Calculated,
%: N 5.81; P 6.42.
N-[Diphenyl(3-phenyl-2-triazenylidene)phos-
phoranyl]-N-phenyltrifluoroacetamide (IIIa).
A
solution of 0.0016 mol of phenyl azide in 10 ml of
hexane was added at 0 C to a suspension of
0.0016 mol of N-(diphenylphosphino)-N-phenyltri-
fluoroacetamide (Ia) in 30 ml of hexane. The mixture
was left overnight, and the precipitate was filtered off
and washed with 20 ml of hexane. Yield 98%, mp
N-Methyl-N-[N-(4-nitrophenyl)diphenylphos-
phorimidoyl]trifluoroacetamide (IVc). A solution
of 0.0643 mol of p-nitrophenyl azide in 5 ml of
benzene was added to a solution of 0.0643 mol of N-
(diphenylphosphino)-N-methyltrifluoroacetamide (Ib)
in 10 ml of benzene, and the mixture was left over-
night. The solvent was removed in a vacuum, and the
oily material that separated crystallized when ground
in hexane. Yield 84%, mp 45 47 C. IR spectrum
1
110 112 C (decomp.). IR spectrum (KBr), , cm :
1710 (C=O), 1380 (P=N), 2130 (P=N N=N). 1H
NMR spectrum (CDCl3), , ppm: 6.85 7.15 m (5H,
Harom, NPh), 7.31 7.65 m (10H, Harom, Ph2P), 7.82
7.96 m (5H, Harom, P=NPh). 19F NMR spectrum
(benzene), F, ppm: 67.79. 31P NMR spectrum
(benzene), P, ppm: 0.19 m. Found, %: N 10.97; P
6.43. C26H20F3N4OP. Calculated, %: N 11.38; P 6.29.
1
1
(KBr), , cm : 1710 (C=O), 1300 1340 (P=N). H
NMR spectrum (CDCl3), , ppm: 3.4 d.q (NCH3, 3JHP
8.8, JHF 1.6 Hz), 7.45 8.06 m (Harom). 19F NMR
5
N-[[3-(4-Fluorophenyl)-2-triazenylidene]di-
phenylphosphoranyl]-N-phenyltrifluoroacetamide
(IIIb). A solution of 0.0027 mol of p-fluorophenyl
azide in 10 ml of hexane was added at 0 C to a sus-
pension of 0.0027 mol of compound Ia in 30 ml of
hexane. The mixture was left overnight, and the pre-
cipitate was filtered off and washed with 20 ml of
hexane. Yield 97%, mp 67 70 C (decomp.). IR spec-
spectrum (benzene), F, ppm: 71.20. 31P NMR spec-
trum (benzene), P, ppm: 14.25 m. Found, %: N 9.17;
P 6.93. C21H17F3N3O3P. Calculated, %: N 9.39; P
6.92.
N-Methyl-N-[N-(4-nitrophenyl)diethoxyphos-
phorimidoyl]trifluoroacetamide (IVd). A solution
of 0.0643 mol of p-nitrophenyl azide in 10 ml of
benzene was added to a solution of 0.0111 mol of N-
(diethoxyphosphino)-N-methyltrifluoroacetamide (Ic)
in 5 ml of benzene. The mixture was left overnight,
the solvent was removed in a vacuum, and the residue
was subjected to a water-jet-pump vacuum. Yield
1
trum (KBr), , cm : 1715 (C=O), 1380 (P=N), 2120
(P=N N=N). H NMR spectrum (CDCl3), , ppm:
6.79 7.22 m (5H, Harom, NPh), 7.39 7.66 m (10H,
1
Harom, Ph2P), 7.85 d (2H, Harom), 7.89 d (2H, Harom
,
J 7.5 Hz). 19F NMR spectrum (benzene), F, ppm:
67.99 (CF3), 125.50 (F). 31P NMR spectrum
(benzene), P, ppm: 0.58. Found, %: N 10.14; P 6.06.
C26H19F4N4OP. Calculated, %: N 10.98; P 6.07.
1
97%, yellow oil. IR spectrum (CCl4), , cm : 1715
(C=O), 1320 1350 (P=N). 1H NMR spectrum
3
(CDCl3), , ppm: 1.32 t (6H, CH2CH3, J 7 Hz),
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 9 2005

1378
SHALIMOV et al.
3
5
3.41 d.q (3H, NCH3, JHP 9.2, JHF 1.6 Hz), 4.04
roacetimidoyl]phosphoramidate (Vd). A solution
of 0.0072 mol of compound IVd in 5 ml of toluene
was refluxed for 4 h. The solvent was removed in a
vacuum, and the residue was crystallized from ben-
zene. Yield 75%, mp 113 115 C. IR spectrum (KBr),
4.32 m (8H, OCH2). 19F NMR spectrum (benzene),
,
F
ppm: 71.03. 31P NMR spectrum (benzene), P, ppm:
8.05. Found, %: N 11.18; P 8.01. C13H17F3N3O5P.
Calculated, %: N 10.96; P 8.08.
1
, cm : 1610 (C=C), 1670 (C=N), 1200 1230 (P=O).
1H NMR spectrum (CDCl3), , ppm: 2.61 d (3H,
NCH3, 3JHP 12.3 Hz), 1.30 t (3H, OCH2CH3, J 7 Hz),
4.00 4.30 m (8H, OCH2CH3). 19F NMR spectrum
(benzene), F, ppm: 71.10. 31P NMR spectrum
(benzene), P, ppm: 1.50. Found, %: N 10.93; P 8.10.
C13H17F3N3O5P. Calculated, %: N 10.96; P 8.08.
N,N -Diphenyl-N-(diphenylphosphinoyl)triflu-
oroacetimidamide (Va). A solution of 0.0037 mol of
compound IVa in 5 ml of xylene was refluxed for
10 h and then reduced by 2/3 in a vacuum. The re-
sidue was diluted with 2 ml of hexane, and the pre-
cipitate was filtered off. Yield 79%, mp 139 140 C.
IR spectrum (KBr), , cm : 1590, 1660 (C=C),
1160 1210 (P=O). H NMR spectrum (acetone-d6), ,
ppm: 6.99, 7.15, 7.3 m (5H, Harom, NPh), 7.43
1
1
REFERENCES
7.66 m (10H, Harom, Ph2P), 7.84 8.01 m (5H, Harom
,
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59.71. 31P NMR spectrum (benzene), P, ppm: 30.60.
Found, %: N 6.09; P 6.71. C26H20F3N2OP. Calculated,
%: N 6.03; P 6.67.
N -(4-Fluorophenyl)-N-(diphenylphosphinoyl)-
N-phenyltrifluoroacetimidamide (Vb). A solution
of 0.0021 mol of compound IVb in 5 ml of xylene
was refluxed for 10 h and then reduced in a vacuum
by 2/3. The residue was diluted with 2 ml of hexane,
and the precipitate was filtered off. Yield 83%, mp
2. Chernega, A.N., Antipin, M.Ya., Struchkov, T.Ya.,
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1
143 144 C. IR spectrum (KBr), , cm : 1670, 1610
1
(C=C), 1190 1230 (P=O). H NMR spectrum (ace-
tone-d6), , ppm: 7.01 7.27 m (5H, Harom, NPh),
7.38 7.64 m (10H, Harom, Ph2P), 8.25 d (2H, Harom),
8.30 d (2H, Harom). 19F NMR spectrum (benzene),
,
F
ppm: 58.80 (CF3), 116.07 (F). 31P NMR spectrum
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C26H19F4N2OP. Calculated, %: N 5.81; P 6.42.
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N-(Diphenylphosphinoyl)-N-methyl-N -(4-nitro-
phenyl)trifluoroacetimidamide (Vc). A solution of
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refluxed for 6 h. The solvent was removed in a va-
cuum, and the residue was crystallized from benzene.
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Yield 90%, mp 100 102 C. IR spectrum (KBr),
,
1
1
cm : 1180 1250 (P=O), 1620 (C=N). H NMR spec-
3
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trum (acetone-d6), , ppm: 3.15 d (3H, CH3, JHP
8.5 Hz), 7.08 8.09 m (28H, Harom). 19F NMR spec-
trum (acetone-d6), F, ppm: 75.53 d (4JFP 9.2 Hz).
31P NMR spectrum (acetone-d6), P, ppm: 30.97.
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lated, %: N 9.39; P 6.92.
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