Synthesis and characterization of tris[2,3-di(o-oxyphenylene)quinoxalin] cyclotriphosphazene - A novel spiroheterocyclophosphazene

Article abstract of DOI:10.1080/10426500307787

Hexachlorocyclotriphosphazene (NPCl₂)₃, reacted with 2,3-di(o-hydroxyphenylene)quinoxalin in the presence of a base, to yield tris[2,3-di(o-oxyphenylene)quinoxalin]cyclotriphosphazene. The synthesis of 2,3-di(o-hydroxy phenylene)quin

Full text of DOI:10.1080/10426500307787

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Synthesis and Characterization of Tris[2,3-di(o-
oxyphenylene)quinoxalin]cyclotriphosphazene--A
Novel Spiroheterocyclophosphazene
Abbas Tarassoli a & Mohammad Reza Shushizadeh a
a Shahid Chamran University , Ahvaz, Iran
Published online: 27 Oct 2010.
To cite this article: Abbas Tarassoli & Mohammad Reza Shushizadeh (2003) Synthesis and Characterization of Tris[2,3-di(o-
oxyphenylene)quinoxalin]cyclotriphosphazene--A Novel Spiroheterocyclophosphazene, Phosphorus, Sulfur, and Silicon and the
Related Elements, 178:4, 803-809, DOI: 10.1080/10426500307787
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Phosphorus, Sulfur and Silicon, 2003, Vol. 178:803–809
C
Copyright 2003 Taylor & Francis
1042-6507/03 $12.00 + .00
DOI: 10.1080/10426500390197968
SYNTHESIS AND CHARACTERIZATION
OF TRIS[2,3-DI(O-OXYPHENYLENE)QUINOXALIN]
CYCLOTRIPHOSPHAZENE—A NOVEL
SPIROHETEROCYCLOPHOSPHAZENE
Abbas Tarassoli and Mohammad Reza Shushizadeh
Shahid Chamran University, Ahvaz, Iran
(Received June 4, 2002; in final form August 2, 2002)
Hexachlorocyclotriphosphazene (NPCl2)3, reacted with 2,3-di(o-
hydroxyphenylene)quinoxalin in the presence of a base, to yield tris[2,3-
di(o-oxyphenylene)quinoxalin]cyclotriphosphazene. The synthesis of
2,3-di(o-hydroxy phenylene)quinoxaline was carried out through three
steps: benzoin condensation, oxidation, and reaction of diketone with
diamine. The products were characterized by 1HNMR, 31PNMR, IR,
and mass spectral data.
Keywords: Cyclotriphosphazene; quinoxalin; salicylaldehyde; spectral
data; synthesis
Chlorocyclophosphazenes form an important class of inorganic hete-
rocyclic ring systems and lie at the interface between organic and
inorganic chemistry.1 The nucleophilic substitution reaction, involving
replacement of labile P Cl bonds by nucleophiles such as aliphatic
and aromatic amines, alcohols, and phenols have been extensively
8
investigated.2 The synthesis, characterization, polymerization, in-
clusion behavior and preliminary crystal structure of tris(o-phenylene-
dioxy)cyclotriphosphazen tris(diphenyl-2,20-dioxy)cyclotriphosphazene,
and tris(o-phenylenediamino) cyclotriphosphazene previously were
12
reported.9
The clathration host properties of several spirocyclophospha-
15
zenes including tris(2,3-naphtalenedioxy)-cyclotriphosphazene13
Address correspondence to Abbas Tarassoli, Shahid Chamran University, Chemistry
Department, College of Sciences, Ahvaz, Iran.
803

804
A. Tarassoli and M. R. Shushizadeh
tris(1,8-naphtalenedioxy)cyclotriphosphazene,16 tris(3,6-dimethylphe-
nylenedioxy)-cyclotriphosphazene17 also are known.
This article describes the synthesis and characterization of another
trimeric phosphazene which contains cyclic groups attached to the phos-
phorus atoms that form a 9-member, spiro-heterocyclic ring compound,
tris[2,3-di(o-oxyphenylene) quinoxalin]cyclotriphosphazene, 1.
RESULTS AND DISCUSSION
Synthesis and Characterization of Tris[2,3-
di(o-oxyphenylene)quinoxalin] Cyclotriphosphazene 1
The general reaction scheme used for the preparation of the cyclized
compound is the typical reaction of hexachlorotriphosphazene with an
aromatic difunctional phenol in the presence of a base.18,19

Novel Spiroheterocyclophosphazene
805
Accordingly, hexachlorocyclotriphosphazene 2 was treated with
three molar equivalents of 2,3-di(o-hydroxyphenylene)quinoxaline
4 in the presence of solvent and base, to yield tris[2,3-di(o-
oxyphenylene)quinoxaline]cyclotriphosphazene 1.
The ability of tris(o-phenylenedioxy)cyclotriphosphazene, 2,3-
dioxynaphthyl compound, and others to polymerize by phosphazene
ring cleavage when heated above 250 C were reported previously,11
whereas the compound 1, tris[2,3-di(o-oxyphenylene) quinoxaline] cy-
clotriphosphazene, was resistant to polymerization or decomposition at
tempratures up to 300 C. In this case, steric widening of the O P O
angle may serve to stabilize the cyclic trimeric structure relative to the
large cyclic or open-chain homologies.20
The synthesis of 2,3-di(o-hydroxyphenylene)quinoxaline was carried
out through three steps: (1) benzoin condensation of salicylaldehyde,
where aromatic aldehydes treated with an alkali metal cyanide, usu-
ally in aqueous solution, undergo condensation to yield the hydrox-
yketone or benzoin; (2) oxidation, where oxidation of -hydroxyketone
with concentrated nitric acid yields the diketone; and (3) reaction
of the resultant diketone with o-phenylenediamine yields 2,3-di(o-
hydroxyphenylene)quinoxaline.
Spectral Data
The principal infrared bands for 1 to 4 as KBr plates are shown in
Table I.
An important feature of the spectra concerns the position of the
phosphorus–nitrogen stretching peak (asymmetrical ring stretching
1
mode) in the 1200 cm region. In general, electron withdrawal by the
side groups should raise the frequency of this band partly due to the
bond strengthening which results from the greater d
P character
22
1
in these circumstance.21
The HNMR data for the compounds 1, 3,
4 and 31PNMR data for 1 obtained in suitable solvents are shown in
Table II.
X-ray diffraction results show that the O
P O angle in tris (o-phenylenedioxy) cy-
clotriphosphazene is 97 . Compare this with the value of 102 reported for (NPCl2)3.

806
A. Tarassoli and M. R. Shushizadeh
TABLE I Infrared Bands for Compounds 1–4
Compound
number
1
Infrared data (cm
)
1
1555, 1487 (C N); 1625, 1425 (C C aromatic); 1374–1284 (C O)
935 (P Ar); 1170, 1202 (P N); 750, 880 (C H aromatic)
O
2
3
519, 610 (PCl2); 837, 1177 (P N)
3500 (O H); 3000–2800 (C H, CHOH); 1700 (C O); 770–730
(C H aromatic)
4
3500–3200 (O H); 1550–1450 (C N); 1470, 1380 (C C aromatic);
680, 740 (C H aromatic)
Proton NMR spectra were used to confirm the structures of compound
number 1, 3, and 4. The spectrum of 3 showed aromatic protons with
chemical shifts at 7.5–8.5 ppm, phenolic OH protons, alcoholic OH
protons and none-aromatic CH protons in the ratio of 8:2:1:1 respec-
tively. The spectrum of 4 also showed aromatic protons with chemical
shifts at 7.8–9 ppm and phenolic OH protons in the ratio of 12:2.
The spectrum of 1 showed only aromatic protons .The aromatic pat-
tern could be rationalized in terms of 1,2-substitution.23 The 31PNMR
of the final product, 1, indicated the presence of a single enviroment for
the phosphorus atom.
The mass spectrum also was employed to confirm the structure of
4. The spectrum of 2,3-di(o-hydroxyphenylene)quinoxaline showed the
stable radical-cation or cation species might be formed from the frag-
mentation of molecular ion[C20H14N2O2]+ with m/e = 314.
The fragmentation of 4 was as follows:
Owing to the high melting point of 1, reliable mass data were not
obtained for this compound.

Novel Spiroheterocyclophosphazene
807
TABLE II NMR Spectra Data for Compounds 1, 3, and 4
Compound
number
NMR data (chemical shift in ppm)a
1HNMR 7.8–9, m (in CCl4)
1
31PNMR
4.5 (in CCl4 + CS2)
3
4
1HNMR 7.5–8.5 (8H, m); (2H, s), 4.9 (1H, s); 2.4 (1H, s) (in CD3COCD3)
1HNMR 7.8–9 (12H, m); 5.3 (2H, s) (in CCl4 + CS2)
a1H and 31PNMR data in ppm relative to TMS and phosphoric acid respectively.
EXPERIMENTAL
Material
Hexachlorocyclotriphosphazene was synthesized from the reaction of
phosphorus pentachloride (99%, Merck) with ammonium chloride (99%,
Merck) in dichlorobenzene (99%, Merck) as a solvent.18 Petroleum
ether (b.p. = 50–70 C, Merck), sodium cyanide (95%, Merck), ethanol
(99%, Merck), salicylaldehyde (PROLABO), nitric acid (65%, Merck),
o-phenylenediamine (98%, Merck), sodium carbonate (99.5%, Merck),
tetrahydrofurane (99%, Merck), and xylene (>99%, Merck) were
purchased.
2,20-Dihydroxy Benzoin
In a 100 ml beaker was placed 10.1 ml (0.1 mmol) of salicylaldehyde
(d = 1.16 g/ml), 25 ml of ethanol and a solution of 1 g (0.02 mmol) of
sodium cyanide in 50 ml of water. The mixture was stirred and cooled
in an ice bath.
The crude product was filtered, washed with 50% ethanol-water,
drained, and dried. Melting point of crude 2,20-dihydroxy benzoin, which
is yellow in color, is 158–159 C (yield 90%).
2,20-Dihydroxy Benzil
11.5 g (0.047 mmol) of crude 2,20-dihydroxy benzoin and 50 ml of con-
centrated nitric acid were heated on a boilling water bath with occa-
sional shaking until the evolution of nitrogen dioxides has ceased (about
45 min). The reaction mixture was poured into 140 ml of cold water and
stirred well until it crystallized completely as a yellow solid. The crude
2,20-dihydroxy benzil was filtered and washed thoroughly with cold wa-
ter to remove the nitric acid. Recrystallization from 40 ml of ethanol
(95%). Melting point of 2,20-dihydroxy benzil is 118–119 C (yield
85%).

808
A. Tarassoli and M. R. Shushizadeh
2,3-Di(o-hydroxy phenylene)quinoxaline
To a warm solution of 2.42 g (0.01 mmol) of 2,20-dihydroxybenzil in
8 ml of absolute ethanol was added a solution of 1.1 g (0.01 mmol) of
o-phenylenediamine in 8 ml of absolute ethanol. It was warmed in a
water bath for 30 min, then water was added until a slight cloudiness
formed; it was then allowed to cool. Filteration and recrystallization
from aqueous ethanol, had a m.p. of 145–146 C (yield 50%).
Tris [2,3-Di(o-oxyphenylene)quinoxaline]-
cyclotriphosphazene
A mixture of hexachlorocyclotriphosphazene (5 g, 0.0144 mmol) 2,3-
di(o-hydroxyphenylene) quinoxaline (12.56 g, 0.0432 mmol), sodium
carbonate (9.16 g, 0.0864 mmol), and tetrahydrofurane (500 ml) was
refluxed for a total of 17 h and was stirred at 25 C for a further 40 h.
The white residue was then filtered off and washed with a large excess
of water until the washing were no longer basic to litmus. A portion of
the residue was recrystallized from xylene at 200 C. It produced white-
yellow crystals of tris[2,3-di(o-oxyphenylene) quinoxaline] cyclotriphos-
phazene which did not melt up to 300 C (yield 38%).
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