Mendeleev Commun., 2009, 19, 263–265
80
1a
(COCl)2
NaOCN, [MgCl2]
RR'P(O)OH
6, 7
[RR'P(O)Cl]
8, 9
70
60
50
40
30
20
10
~20 °C, CH2Cl2
~20 °C, MeCN
n-C8H17NH2
[RR'P(O)NCO]
10, 11
RR'P(O)NHC(O)NH(n-C8H17
3, 4
)
~20 °C
3
2
3, 6, 8, 10 R = R' = n-hexyl
4, 7, 9, 11 R = R' = cyclohexyl
4
Scheme 2
0
1
2
3
4
5
6
7
8
CHNO /mol dm–3
3
phosphinic (9) chlorides in 98 and ~100% yields, respectively
(according to 31P{1H} NMR spectra), which were further reacted
(without additional purification) with sodium cyanate to produce
di-n-hexylphosphoryl (10) and dicyclohexylphosphoryl (11)
isocyanates. The reaction of these isocyanates with n-octyl-
amine leads to phosphorylureas 3 and 4 in 83 and 72% yields,
respectively.
Note that the developed one-pot processes do not require
the isolation of intermediate hydrolytically unstable compounds
(phosphoryl chlorides 8, 9 and phosphoryl isocyanates 5, 10
and 11) in an individual state, all process stages proceed at
ambient temperature, and target ureas 2–4 are obtained in
rather high yields and in high purity. The structure of the ureas
was confirmed by elemental analysis data, IR and 1H and
31P{1H} NMR spectra.‡
The study of the ability of N-diorganophosphorylureas 1a
and 2–4 to extract UVI from nitric acid solutions showed that
the replacement of one (urea 2) or two phenyl groups (urea 3)
with normal alkyl fragment results in a substantial (almost three-
fold) decrease in extractive power as compared with reference
N-diphenylphosphorylated urea 1a. For urea 4, where both phenyl
fragments are replaced with their fully hydrogenated analogues,
cyclohexyl substituents, the extractive power decreases by almost
40 times (Figure 1).
Taking into account that ureas 1a and 2–4 have identical
terminal nitrogen-containing fragments and differ only in the
nature of organic substituents connected to the phosphorus
atom via C–P bonds, it is safe to associate the high extractive
power of N-diphenylphosphorylated ureas of type 1 toward
uranium(VI) with the AAS effect.
Figure 1 Extraction of UVI with 0.05 mol dm–3 solutions of N-diorgano-
phosphoryl-N'-n-octylureas 1a, 2–4 in chloroform depending on HNO3
concentration (phase ratio of 1:1).
Thus, on the basis of our experimental data, we can draw
a conclusion that the ‘anomalous aryl strengthening’ effect is
observed not only for methylenediphosphine dioxides and car-
bamoylmethylphosphine oxides but also for N-diorganophos-
phorylureas; that is, this effect has a rather general character in
the series of bidentate neutral organophosphorus compounds.
This work was supported by the Russian Foundation for Basic
Research (project nos. 05-03-08017-ofi_e and 08-03-12153-ofi)
N-Di-n-hexylphosphoryl-N'-n-octylurea 3. Freshly distilled oxalyl
chloride (0.9 g, 7.1 mmol) was added dropwise over 25 min to a mag-
netically stirred solution of 1.090 g (4.7 mmol) of phosphinic acid 6 in
10 ml of anhydrous CH2Cl2 in an argon atmosphere at ambient tempera-
ture, the mixture was stirred for additional 1.5 h at the same temperature,
volatile products were removed in a vacuum from the reaction mixture
containing chlorophosphinate 8 (d 31P-{1H} 73.46 ppm). The residue was
dissolved in 10 ml of anhydrous MeCN, 11 mg (0.115 mmol) of finely
divided anhydrous MgCl2 was added to the solution, the mixture was stirred
until complete dissolution of MgCl2, 0.61 g (9.4 mmol) of NaOCN was
added, and the suspension was stirred for 11.5 h at ambient temperature.
n-Octylamine (607 mg, 4.7 mmol) was added dropwise to the resultant reac-
tion mixture containing phosphoryl isocyanate 10 (d 31P-{1H} 44.10 ppm),
the mixture was stirred for 1 h at ambient temperature, 17 ml of distilled
water was added, and the mixture was stirred for 1 h at ambient tempe-
rature. The precipitate was collected by filtration, washed with distilled
water (4×12 ml), and dried in air to give 1.50 g (83%) of compound 3 as
a white crystalline solid, mp 98–99 °C (from heptane). 31P{1H} NMR,
d: 52.74. 1H NMR, d: 0.86 (t, 9H, Me, 3JHH 6.7 Hz), 1.10–1.69 [m, 28H,
Me(CH2)6 + Me(CH2)4], 1.72–2.13 (m, 4H, CH2P), 3.12 (dt, 2H, CH2NH,
‡
The NMR spectra were recorded on a Bruker AV-400 spectrometer
3JCHH 6.7 Hz, JNHH 6.2 Hz), 6.03 (br. s, 1H, CH2NH), 7.94 [br. s, 1H,
3
operating at 400.13 (1H) and 161.98 MHz (31P) in CDCl3 solutions using
the signals of residual protons of the deuterated solvent as an internal
reference for 1H NMR and 85% H3PO4 as an external reference for
31P NMR. The IR spectra were obtained on a UR-20 spectrometer as
KBr pellets. Di-n-hexylphosphinic acid 6 and dicyclohexylphosphinic
acid 7 were obtained according to literature procedures.11,12
NHP(O)]. IR (KBr, n/cm–1): 3320, 3160, 3100 (NH), 1710, 1700, 1680
(C=O), 1165 (P=O). Found (%): C, 64.76; H, 11.63; N, 7.07; P, 8.01.
Calc. for C21H45N2O2P (%): C, 64.91; H, 11.67; N, 7.21; P, 7.97.
N-Dicyclohexylphosphoryl-N'-n-octylurea 4. Freshly distilled oxalyl
chloride (0.9 g, 7.1 mmol) was added dropwise over 25 min to a mag-
netically stirred solution of 1.090 g (4.7 mmol) of phosphinic acid 7 in
10 ml of anhydrous CH2Cl2 in argon atmosphere at ambient tempera-
ture, the mixture was stirred for additional 1.5 h at the same temperature,
volatile products were removed in a vacuum from the reaction mixture
containing chlorophosphinate 9 (d 31P-{1H} 82.22 ppm). The residue was
dissolved in 10 ml of anhydrous MeCN, 11 mg (0.115 mmol) of finely
divided anhydrous MgCl2 was added to the solution, the mixture was stirred
until complete dissolution of MgCl2, 0.61 g (9.4 mmol) of NaOCN was
added, and the suspension was stirred for 17.5 h at ambient temperature.
n-Octylamine (607 mg, 4.7 mmol) was added dropwise to the resultant reac-
tion mixture containing phosphoryl isocyanate 11 (d 31P-{1H} 49.46 ppm),
and the mixture was stirred for 1 h at ambient temperature. The subsequent
treatment as in the synthesis of compound 3 afforded 1.30 g (72%) of
compound 4 as a white crystalline solid, mp 139–141 °C (from chloro-
N-Methyl(phenyl)phosphoryl-N'-n-octylurea 2. Finely divided anhydrous
MgCl2 (14 mg, 0.147 mmol) was added to a solution of 1.015 g (5.7 mmol)
of chlorophosphinate 4 in 10 ml of anhydrous MeCN, the mixture was
stirred until complete dissolution of MgCl2, 0.74 g (11.4 mmol) of NaOCN
was added, and the suspension was stirred for additional 1 h at ambient
temperature. n-Octylamine (0.738 g, 5.7 mmol) was added dropwise
to the resultant reaction mixture containing phosphoryl isocyanate 5
(d 31P-{1H} 26.65 ppm) and the suspension was stirred for 1 h, MeCN
was removed in a vacuum, 20 ml of distilled water was added to the
residue, and the mixture was stirred for 1 h. The precipitate was collected
by filtration, washed with distilled water (4×20 ml), and dried in air to give
1.55 g (88%) of compound 2 as a white crystalline solid, mp 149–151 °C
1
(from chloroform–hexane). 31P{1H} NMR, d: 33.68. H NMR, d: 0.85
[t, 3H, Me(CH2)7, 3JHH 6.7 Hz], 1.10–1.33 [m, 10H, Me(CH2)5], 1.34–1.50
1
form–hexane). 31P-{1H} NMR, d: 52.25. H NMR, d: 0.86 (t, 3H, Me,
2
(m, 2H, CH2CH2NH), 1.91 (d, 3H, MeP, JHP 14.7 Hz), 3.10 (dt, 2H,
3JHH 6.8 Hz), 1.13–1.53 [m, 22H, Me(CH2)6 + cyclo-C6H11], 1.60–2.03 (m,
12H, cyclo-C6H11), 3.15 (dt, 2H, CH2NH, 3JCHH 6.8 Hz, 3JNHH 6.0 Hz),
6.50 (br. s, 1H, CH2NH), 6.96 [br. s, 1H, NHP(O)]. IR (KBr, n/cm–1):
3320, 3080 (NH), 1700 (C=O), 1210, 1180 (P=O). Found (%): C, 65.57;
H, 10.79; N, 7.41; P, 7.92. Calc. for C21H41N2O2P (%): C, 65.59; H, 10.75;
N, 7.28; P, 8.05.
CH2NH, 3JCHH 6.5 Hz, 3JNHH 6.4 Hz), 6.35 (br. s, 1H, CH2NH), 7.35–7.48
3
(m, 2H, m-Ph), 7.52 (t, 1H, p-Ph, JHH 7.1 Hz), 7.78 (dd, 2H, o-Ph,
3JHH 7.7 Hz, 3JHP 12.7 Hz), 8.44 [d, 1H, NHP(O), 2JHP 7.5 Hz]. IR (KBr,
n/cm–1): 3330, 3150, 3100 (NH), 1700, 1680 (C=O), 1180 (P=O). Found
(%): C, 61.94; H, 8.75; N, 9.08; P, 9.92. Calc. for C16H27N2O2P (%): C,
61.92; H, 8.77; N, 9.02; P, 9.99.
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