A novel synthesis of hexasubstituted cyclotriphosphazenes

Article abstract of DOI:10.1081/SCC-120002003

Hexaaryloxyphosphazenes [N₃P₃(O-C₆H₄-R)₆] (R=H, CH₃, OCH₃, C(CH₃)₃, CHO, COCH₃, COOR, C₆H₅, NO₂, F, etc) were readily obtained with ca 70% isolated yield in refluxing acetonitrile in the presence of anhydrous potassium phosphate. All compounds were characterized by means of elemental analysis, ¹H-NMR, ³¹P-NMR spectroscopy.

Full text of DOI:10.1081/SCC-120002003

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A NOVEL SYNTHESIS OF HEXASUBSTITUTED
CYCLOTRIPHOSPHAZENES
Chengfeng Ye a , Zefu Zhang a & Weimin Liu b
a State Key Laboratory of Solid Lubrication , Lanzhou Institute of Chemical Physics ,
Chinese Academy of Sciences , Lanzhou, 730000, P. R. China
b State Key Laboratory of Solid Lubrication , Lanzhou Institute of Chemical Physics ,
Chinese Academy of Sciences , Lanzhou, 730000, P. R. China
Published online: 16 Aug 2006.
To cite this article: Chengfeng Ye , Zefu Zhang & Weimin Liu (2002) A NOVEL SYNTHESIS OF HEXASUBSTITUTED
CYCLOTRIPHOSPHAZENES, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 32:2, 203-209, DOI: 10.1081/SCC-120002003
To link to this article: http://dx.doi.org/10.1081/SCC-120002003
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SYNTHETIC COMMUNICATIONS, 32(2), 203–209 (2002)
A NOVEL SYNTHESIS OF
HEXASUBSTITUTED
CYCLOTRIPHOSPHAZENES
Chengfeng Ye, Zefu Zhang, and Weimin Liu*
State Key Laboratory of Solid Lubrication,
Lanzhou Institute of Chemical Physics,
Chinese Academy of Sciences,
Lanzhou 730000, P. R. China
ABSTRACT
Hexaaryloxyphosphazenes [N3P3(O-C6H4-R)6] (R¼H, CH3,
OCH3, C(CH3)3, CHO, COCH3, COOR, C6H5, NO2, F, etc)
were readily obtained with ca 70% isolated yield in reflux-
ing acetonitrile in the presence of anhydrous potassium
phosphate. All compounds were characterized by means of
1
elemental analysis, H-NMR, 31P-NMRspectroscopy.
In recent years, many efforts were focused on the preparation and
characterization of phosphazenes which contain a framework of alternating
phosphor and nitrogen atoms with two substituent groups attached to each
phosphor atom.1 It is noticeable that cyclophosphazenes, especially hexa-
aryloxyphosphazenes and perfluoroaryloxyphosphazenes exhibit excellent
thermal and chemical stability which can be used as fireproof materials,
*Corresponding author.
203
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

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YE, ZHANG, AND LIU
high temperature lubricants, vacuum pump oils and hard disk surface
lubricants.2–4 To meet the need of the both scientific and technological
purposes, a wide variety of hexaaryloxyphosphazenes were prepared. The
synthetic method usually involved the reaction of hexachlorocyclotriphos-
phazene [N3P3Cl6] with sodium phenolates in an appropriate organic
solvent.5 However, this method required a long time. Therefore several
studies have been reported to improve the preparation.6–8
Some authors found that phase-transfer catalyst (PTC) can accelerate
the substitution reaction.6–7 However this method some times resulted in the
mixture of various substituted phosphazenes. G.A. Carriedo et al.8 des-
cribed a very convenient preparation for some known cyclic aryloxy-
phosphazenes directly from [N3P3Cl6], phenols and K2CO3 in acetone.
But in the case of phenols HOC6H4-R(R ¼H, But, OCH3), the reactions
were much slower, lasting 20 h even in the presence of PTC.
Scheme.
In the present paper, we describe a novel and efficient method of
preparation hexaaryloxyphosphazenes that linked either electron-donor or
electron-acceptor group. As shown in the scheme, in refluxing acetonitrile,
hexasubstituted aryloxycyclotriphosphazenes can be readily synthesized by
reaction of N3P3Cl6 with phenols in the presence of anhydrous potassium
phosphate.
Anhydrous potassium phosphate was reported to be used in the one-
pot synthesis of dithiocarbamates.9–10 A series of experiments show that
potassium phosphate is more effective than potassium carbonate in the
catalysis of reactions of N3P3Cl3 with phenols. While the reaction of
N3P3Cl3 with phenol (R¼H) was performed in acetone/K2CO3 for 3 h or
toluene/K2CO3 for 16 h, it cannot result in the hexaphenoxycyclotri-
phosphazene which can be obtained by the reaction in acetonitrile/K3PO4
for 3 h with 75% isolated yield.

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HEXASUBSTITUTED CYCLOTRIPHOSPHAZENES
205
In the case of phenol 2c (R¼But), the reaction was also very fast. 3c
was prepared in acetone-K2CO3 for 20 h in the presence of tetrabutyl ammo-
nium bromide (TBAB)8 or using thallium 4-tert-butyl-phenoxide and TBAB
in refluxing THF for 12 h.11 In contrast, using acetonitrile/K3PO4 method
without TBAB, the reaction can be completed within 10 h. It is also found
that by this method the reaction times of phenols 2a, 2b (R¼CH3, OCH3)
could be substantially shortened.
In addition, some other types compounds containing hydroxyl group
such as methyl salicylic ester, 4-fluoro-3-trifluoromethyl phenol, 2-naphtha-
lenol also can easily react with N3P3Cl6 in acetonitrile/K3PO4 to afford
corresponding aryloxyphosphazenes, so the long workups and tedious
chromatography can be avoided.
EXPERIMENTAL
The FT-IRspectra were recorded with Bio-Rad Win-IRspectrometer.
NMRspectra were measured on Varian FT-80A NMRspectrometer, using
1
CDCl3 as the solvent for H-NMRas well as CDCl /C6D6 for 31P-NMR.
3
The chemical shifts for 31P-NMRspectra are relative to the external stan-
dard of 85% phosphoric acid. C, H, N analyses were performed with a
CE-1106 microanalyzer.
Typical Procedure: Hexachlorocyclotriphosphazene (1.0 g, 2.87 mmol),
substituted phenol (18.10 mmol), anhydrous potassium phosphate (7.0 g,
32.97 mmol), and 50 mL of acetonitrile were placed in 100 mL flask con-
nected with a drying tube. The mixture was refluxed for 0.5–10 h, and
then cooled to room temperature. The solid was filtered and washed twice
with 10 mL of acetonitrile. The filtrate and the washings were combined, and
the solvent was distilled under reduced pressure. The residue was dissolved
in ethyl acetate and washed with 10% NaOH solution for three times and
then with water, dried over anhydrous sodium sulfate. After filtration and
evaporation, the product was purified by recrystallization from an appro-
priate solvent (listed in the table).
Hexakis(4-methylphenoxy)cyclotriphosphazene (3a): White solid,
m.p. 119–120ꢀC (lit.12 116–117ꢀC); IR, nmax/cmꢁ1: 1505 (Ph), 1213
(-P¼N-), 968 (P-O); 1H-NMR: d 6.85 (d, J ¼ 8.8 Hz, 12H), 6.78 (d,
J ¼ 8.8 Hz, 12H), 2.25 (s, 18H); 31P-NMR: d 8.89; Anal. Calcd for
C42H42N3O6P3 C, 64.86 H, 5.44 N, 5.40. Found C, 64.70 H, 5.31 N, 5.20
Hexakis(4-methyloxyphenoxy)cyclotriphosphazene (3b): White solid,
m.p. 100–102ꢀC (lit.13100–102ꢀC); IR, nmax/cmꢁ1: 1504 (Ph), 1198 (-P¼N-),
1
971 (P-O); H-NMR: d 6.76 (d, J ¼ 9.6 Hz, 12H), 6.68 (d, J ¼ 9.6 Hz, 12H),

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YE, ZHANG, AND LIU
Table. Reaction Conditions of Phosphazenes
Time
(h)
Recrystallization
Solvent
Yield
(%)
NO
R
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o*
CH3
OCH3
But
H
CHO
COCH3
COOCH3
COOC2H5
COOC4H9
C6H5
NO2
F
4-F-3-CF3
2-COOCH3
–
4
6
10
3
3
2
2
6
10
3
2
ethanol
ethanol
ethanol
ethyl acetate
acetonitrile
ethyl acetate
acetone
methanol
methanol
ethanol
70
67
70
75
70
80
76
72
65
72
78
78
74
70
80
o-dichlorobenzene
methanol
methanol
ethyl acetate
chloroform/hexane
3
3
2.5
0.5
*Compound 3o was Hexakis (2-naphthyloxy) cyclotriphosphazene.
3.73 (s, 18H); 31P-NMR: d 9.80; Anal. Calcd for C42H42N3O12P3 C, 57.74 H,
4.85 N, 4.81. Found C, 57.54 H, 4.64 N, 4.70.
Hexakis(4-tert-butylphenoxy)cyclotriphosphazene (3c): White solid,
m.p. 130–131ꢀC (lit.13 132–133ꢀC); IR, nmax/cmꢁ1: 1509 (Ph), 1203
(-P¼N-), 956 (P-O); 1H-NMR: d 7.14 (d, J ¼ 8.8 Hz, 12H), 6.88 (d, J ¼ 8.8 Hz,
12H), 1.27 (s, 54H); 31P-NMR: d 8.75; Anal. Calcd for C60H78N3O6P3 C,
69.95 H, 7.63 N, 4.08. Found C, 69.83 H, 7.58 N, 3.91.
Hexakisphenoxycyclotriphosphazene (3d): White solid, m.p. 111–112ꢀC
(lit.14 110–111ꢀC); IR,
n
max/cmꢁ1
:
1486 (Ph), 1197 (-P¼N-), 952
(P-O); H-NMR: d 7.18–6.85 (Ar-H); 31P-NMR: d 8.45; Anal. Calcd for
C36H30N3O18P3 C, 62.34 H, 4.36 N, 6.06. Found C, 62.10 H, 4.25 N, 5.94.
Hexakis(4-formylphenoxy)cyclotriphosphazene (3e): White solid,
m.p. 155–158ꢀC (lit.15 154–158ꢀC); IR, nmax/cmꢁ1: 1706 (C ¼ O), 1202
1
1
(-P¼N-), 968 (P-O); H-NMR: d 9.93 (s, 6H), 7.68 (d, J ¼ 8.8 Hz, 12H),
7.19 (d, J ¼ 8.8 Hz, 12H); 31P-NMR:
d
6.90; Anal. Calcd for
C42H30N3O12P3 C, 58.55, H, 3.51 N, 4.88. Found C, 58.34 H, 3.40 N, 4.74.
Hexakis(4-acetophenoxy)cyclotriphosphazene (3f ): White solid,
m.p. 166–168ꢀC (lit.7 167–169ꢀC); IR, nmax/cmꢁ1: 1681 (C ¼ O), 1501 (Ph),
1205 (-P¼N-), 946 (P-O); 1H-NMR: d 7.73 (d, J ¼ 8.8 Hz, 12H), 7.07
(d, J ¼ 8.8 Hz, 12H) 2.57 (s, 18H); 31P-NMR: d 7.37; Anal. Calcd

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207
for C48H42N3O12P3 C, 61.02 H, 4.51 N, 4.43. Found C, 61.29 H, 4.67
N, 4.35.
Hexakis(4-(methoxycarbonyl)phenoxy)cyclotriphosphazene (3g): White
solid, m.p. 152ꢀC; IR, nmax/cmꢁ1: 1725 (C¼O), 1208 (-P¼N-), 958 (P-O);
1H-NMR: d 7.80 (d, J ¼ 8.8 Hz, 12H) 7.04 (d, J ¼ 8.8 Hz, 12H) 3.92 (s, 18H);
31P-NMR: d 6.90; Anal. Calcd for C48H42N3O18P3 C, 55.34 H, 4.06 N, 4.03.
Found C, 55.23 H, 4.01 N, 3.91.
Hexakis(4-(ethoxycarbonyl)phenoxy)cyclotriphosphazene (3h): White
solid, m.p. 87–88ꢀC (lit.16 78–80ꢀC); IR, nmax/cmꢁ1: 1717 (C¼O),
1
1217 (-P¼N-), 958 (P-O); H-NMR: d 7.83 (d, J ¼ 8.8 Hz, 12H), 7.05 (d,
J ¼ 8.8 Hz, 12H), 4.42 (q, J ¼ 7.2 Hz, 12H), 1.40 (t, J ¼ 7.2 Hz, 18H);
31P-NMR: d 7.46; Anal. Calcd for C54H54N3O18P3 C, 57.60 H, 4.83 N,
3.73. Found C, 57.48 H, 4.79 N, 3.60.
Hexakis(4-(butoxycarbonyl)phenoxy)cyclotriphosphazene (3i): White
solid, m.p. 72–73ꢀC; IR, nmax/cmꢁ1: 1711 (C¼O), 1209 (-P¼N-), 954
(P-O); 1H-NMR: d 7.81 (d, J ¼ 8.8 Hz, 12H), 7.04 (d, J ¼ 8.8 Hz, 12H),
4.30 (t, J ¼ 6.4 Hz, 12H), 1.74–1.40 (broad, 24H), 1.04 (t, J ¼ 7.2 Hz, 18H);
31P-NMR: d 7.49; Anal. Calcd for C66H78N3O18P3 C, 61.25 H, 6.07 N, 3.25.
Found C, 61.18 H, 5.99 N, 3.16.
Hexakis(4-phenylphenoxy)cyclotriphosphazene (3j): White solid,
m.p. 199–201ꢀC (lit.17 202–203ꢀC); IR, nmax/cmꢁ1: 1504 (Ph), 1208 (-P¼N-),
1
954 (P-O); H-NMR: d 7.33–6.95 (broad, ArH); 31P-NMR: d 9.33; Anal.
Calcd for C72H54N3O6P3 C, 75.19; H, 4.73; N, 3.65. Found C, 75.10 H, 4.71
N, 3.59.
Hexakis(4-nitrophenoxy)cyclotriphosphazene (3k): This compound was
prepared using typical procedure, crude product washed with acetone then
with water, recrystallised from o-dichlorobenzene. Yield 78%, m.p. 260–
262ꢀC (lit.18 260–264ꢀC); IR, nmax/cmꢁ1: 1526 (Ph), 1202 (-P¼N-), 943
(P-O); C36H24N3O12P3 C, 44.89 H, 2.51 N, 13.08 Found C, 44.71 H, 1.37
N, 12.95.
Hexakis(4-fluorophenoxy)cyclotriphosphazene (3l): White solid,
m.p. 126–127ꢀC (lit.4 127–129ꢀC); IR, nmax/cmꢁ1: 1504 (Ph), 1215 (-P¼N-),
1
957 (P-O); H-NMR: d 6.89 (d, J ¼ 3.2 Hz, 12H), 6.81 (d, J ¼ 3.2 Hz, 12H);
31P-NMR: d 8.95; Anal. Calcd for C36H24F6N3O6P3 C, 53.95 H, 3.02 N,
5.24. Found C, 53.83 H, 2.86 N, 5.06.
Hexakis(2-(methoxycarbonyl)phenoxy)cyclotriphosphazene
(3m):
White solid, m.p. 111ꢀC; IR, nmax/cmꢁ1: 1723 (C¼O), 1206 (-P¼N-), 958
(P-O); 1H-NMR: d 7.72 ꢂ 7.17 (broad, 18H), 3.64 (s, 18H); 1P-NMR: d 6.62;
Anal. Calcd for C48H42N3O18P3 C, 55.34 H, 4.83 N, 3.73. Found C, 57.48
H, 4.79 N, 3.60.
Hexakis(4-fluoro-3-trifluoromethylphenoxy)cyclotriphosphazene (3n):
White solid, m.p. 73ꢀC; IR, nmax/cmꢁ1: 1321 (CF3), 1263 (C-F), 1221

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YE, ZHANG, AND LIU
(-P¼N-), 969 (P-O); 1H-NMR: d 7.26–7.06 (broad, ArH); 31P-NMR: d 8.19;
Anal. Calcd for C42H18F24N3O6P3 C, 41.71 H, 1.50 N, 3.47. Found C, 41.67
H, 1.37 N, 3.23.
Hexakis(2-naphthyloxy)cyclotriphosphazene (3o): This compound was
prepared using typical procedure, crude product washed with acetone then
with water, recrystallized from chloroform/hexane. Yield 80%,
m.p. 166–167ꢀC (lit.19 168–169ꢀC); IR, nmax/cmꢁ1: 1508 (C¼O), 1210
(-P¼N-), 973 (P-O); 1H-NMR: d 7.67–7.02 (ArH); 31P-NMR: d 9.21;
Anal. Calcd for C60H42N3O6P3 C, 72.51 H, 4.26 N, 4.23. Found C, 72.46
H, 4.15 N, 4.20.
ACKNOWLEDGMENTS
We are grateful to the National Natural Science Foundation of China
(grant No. 59825116) and Chinese Academy of Sciences for the financial
support.
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Received in the UK December 4, 2000

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