Synthesis, characterization and epoxidation of hexakis-4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene

Article abstract of DOI:10.1016/j.tetlet.2019.01.003

4-(2-(4-((β-Methallyl)oxy)phenyl)propan-2-yl)phenol was prepared via the reaction of methallyl chloride with bisphenol A and used for the synthesis of hexakis-4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene. It was revealed that th

Full text of DOI:10.1016/j.tetlet.2019.01.003

Accepted Manuscript
Synthesis, characterization and epoxidation of hexakis-4-(2-(4-((β-methall-
yl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene
Evgeniy M. Chistyakov, Sergey N. Filatov, Pavel A. Yudaev, Vyacheslav V.
Kireev
PII:
S0040-4039(19)30004-8
https://doi.org/10.1016/j.tetlet.2019.01.003
TETL 50536
DOI:
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
6 October 2018
30 December 2018
3 January 2019
Please cite this article as: Chistyakov, E.M., Filatov, S.N., Yudaev, P.A., Kireev, V.V., Synthesis, characterization
and
epoxidation
of
hexakis-4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene,
Tetrahedron Letters (2019), doi: https://doi.org/10.1016/j.tetlet.2019.01.003
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Synthesis, characterization and epoxidation of hexakis-4-(2-(4-((β-
methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene
Evgeniy M. Chistyakov, Sergey N. Filatov, Pavel A. Yudaev, Vyacheslav
V. Kireev
D. I. Mendeleyev University of Chemical Technology of Russia, 125047
Moscow, Russian Federation.
Abstract
4-(2-(4-((β-Methallyl)oxy)phenyl)propan-2-yl)phenol was prepared via the
reaction of methallyl chloride with bisphenol A and used for the synthesis of
hexakis-4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-
yl)phenoxycyclotriphosphazene. It was revealed that the latter undergoes the
Claisen rearrangement and can be also epoxidized by 3-chloroperbenzoic acid. The
obtained epoxide was cured by a treatment with isophorone diamine. The
decomposition and glass transition temperatures of cured resin were also estimated
(275 and 130 °C, respectively) by DSC and TGA methods.
Keywords: phosphazene, bisphenol A, epoxidation, epoxi resin, thermostability.
Introduction
Phosphazenes have proved themselves to be beneficial modifiers of various
polymeric materials, improving their performance properties. An introduction of
various functional phosphazenes into polyurethanes allows one to improve their
fire resistance [1], thermal stability, coke content in the residue [2], tensile strength
[3], and hardness and hydrophobicity of coatings containing them [4].
Modification of methyl methacrylate by propyl ester of phosphazene significantly
elevates its initial decomposition temperature [5]. Self cross-linked acrylic latex,
which was obtained via an emulsion polymerization of 2,2,2-trifluoroethyl
methacrylate, methyl methacrylate, butyl acrylate, methacrylic acid, and
hexakisallylaminocyclotriphosphazene, exhibited excellent physico-chemical and
electrochemical properties, and also became more stable due to the incorporated
phosphazene [6]. Propyl ester of phosphazene has also demonstrated a positive
effect on polystyrene properties, i.e., the destruction temperature and residual yield

of coke are increasing along with the phosphazene content in a polymer [7]. The
fire resistance properties of phosphazenes are especially appropriate for a cotton
modification [8], since they can also improve the abrasion hardness of cotton cloth
and its water resistance [9]. An addition of phosphazene-triazine to the polylactide
provided the composition possessing the high value of oxygen limit index (34.3%),
which have successfully passed a test for vertical combustion (the flammability
category of material was V-0) [10]. Hexakis(4-nitrophenoxy)cyclotriphosphazene
was added to polycarbonate, which resulted in the oxygen limit index of polymer
increased by 1.68 times as compared to the pure polycarbonate [11]. It was
possible to increase the modulus of elasticity in flexure and impact resistance of
carbon
fiber
based
on
polyamide
6
via
its
doping
with
hexaphenoxycyclotriphosphazene [12]. Moreover, the value of oxygen limit index
of that fiber was 38.4%, which allows one to utilize it in the aerospace industry.
Epoxy resins obtained from phosphazenes are especially important since they can
be applied in many areas of science and technology. Materials based on
phosphazene-containing epoxy resins can be utilized in electronics, space
technology, military and civil aviation due to their fireproof properties,
hydrophobicity, thermostability, and nontoxicity [13-22], as well as promising
dielectric and mechanical properties [23].
To employ phosphazenes as the most efficient modifiers of epoxy resins, their
compatibility with resin has to be achieved in order to obtain homogeneous
polymer matrix. This could be implemented via the introduction of epoxy groups
into phosphazene. A treatment of various functional phosphazenes with substances
containing epoxy groups is one among the common synthetic approaches to such
compounds [17,22,24]. However, this method may be accompanied by various side
reactions, e.g., cross-linking. This can usually be avoided by taking the epoxy-
containing reagent in excess to phosphazene, but in such case, the problem of
product purification arises.
Another way to prepare epoxy phosphazenes is the epoxidation of
phosphazenes containing double bonds by peracids [25,26]. This method allows

avoiding intermolecular cross-links, but it has been reported that in the case of
allyloxy groups, the epoxidation of double bonds does not proceed completely.26 It
was suggested that it is caused by the –I effect of oxygen atom, which reduces the
electron density of double bond of the allyl group. The present work was aimed on
the verification of this hypothesis in addition to the increasing degree of
epoxidation of allyl-containing phosphazenes. A replacement of allyloxy groups by
β-methallyloxy ones bearing methyl groups, which cause an +I effect on the
double bonds, was the major approach proposed herein.
Results and discussion
Since the methyl group of 2-methallyloxy moiety can provide steric
hindrances during epoxidation, we have initially decided to carry out a model
reaction between bis-β-methallyl ether of bisphenol A (Scheme 1, compound I)
and 3-CPBA, which resulted in the formation of compound III (see Scheme 1).
Scheme 1. The shown numbering of carbon atoms corresponds to that used in the
description of chemical shifts in 13C NMR (see experimental section).

1
The comparison of H NMR spectra of compound I (Fig. 1,a) and III (Fig.
1,b) allowed us to conclude that the epoxidation of double bonds proceeded
completely. Thus, the next steps were to obtain hexakis-4-(2-(4-((β-
methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene (compound IV)
and to perform its epoxidation, which required to synthesize the monofunctional
derivative of 4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenol (compound II).
However, the problem occurred during the preparation of compound II: since
bisphenol A is the bifunctional compound, an attempt to alkylate only one
hydroxyl group always resulted in a mixture of compounds (bisphenol A,
compounds I and II). To separate this mixture, the special procedure given in
experimental section was developed. Thus, compound II was successfully isolated,
and its 1H NMR spectrum is shown in Fig 1,c.

1
Fig. 1. H NMR spectra of compounds (a) I, (c) II, and (b) III. The numbers
indicate the hydrogen atoms in the compounds and the signals corresponding to
them.
Compound IV was synthesized according to the phenolate method in two
steps. The phenolate was initially prepared by the treatment of compound II with
sodium ethoxide. The reaction of HCP with excess of obtained phenolate was
carried out in diglyme at 120°C, since this was the only way to completely
substitute the chlorine atoms in HCP, which was confirmed by singlet peak in the
31P NMR spectrum of obtained product (Fig. 2,a).

Fig. 2. 31P NMR spectra of compounds (a) IV, (b) V, and (c) III.
Compound IV was initially isolated as a viscous yellow mass. However, this
substance became glassy at room temperature after its reprecipitation from ethanol.
It can be explained by the removal of traces of compound II from the product.
DSC data allowed us to determine the glass transition temperature of compound
IV, which is 30°C (Fig. 3).

Fig. 3. TGA and DSC curves of compounds (A) IV and (B) VI, and (C) those
of compound VI cured with isophorone diamine.
During the further heating, there were no thermal effects observed on the
DSC curve up to the temperature of 210 °C. Above this temperature, there is an
exothermic peak, which could be interpreted as the beginning of destruction.
However, there is no mass loss on the TGA curve at this temperature (see Fig. 3).
This fact could be explained only by the occurrence of exothermic chemical
reaction, e.g., polymerization of double bonds. To reveal the nature of this
reaction, compound IV was heated in a sealed ampoule under inert (Ar)
atmosphere up to 300 °C and investigated using NMR spectroscopy. The
1
comparison of H NMR spectra of initial (Fig. 4,a) and heated (Fig. 4,b) samples
of compound IV can clearly confirm the preservation of double bonds in the heated
sample, which consequently excludes any polymerization processes. However,
there is a difference in the signals of aromatics protons in the heated sample, in
particular, the new singlet appears in the spectrum, which indicates the absence of
two adjacent protons presented earlier. Therefore, the reaction proceeds with the
participation of an aromatic ring and via the substitution of its hydrogen atom. In
addition, there is an upfield shift of signal of the methylene group protons. Taking
into account these observations, it could be concluded that the reason of

exothermic effect was the Claisen rearrangement, which proceeded at the
conversion of 88% (based on the comparison of integral ratios of the proton signals
of isomerized and nonisomerized groups). Thus, compound V was formed in this
reaction (see Scheme 1 for its structure). It should be noted that the phosphazene
cycle was preserved during the rearrangement, which was confirmed by the singlet
peak in the 31P NMR spectrum (see Fig. 2,b).
Fig. 4. 1H NMR spectra of compounds (a) IV, (b) V, and (c) VI. The numbers
indicate the hydrogen atoms in the compounds and the peaks corresponding to
them.
Similarly to the case of model compound I, the epoxidation of allyl groups in
1
compound IV have proceeded completely, which was confirmed by H NMR of
obtained compound VI. It should be noted that the full epoxidation of compound I
takes 48 h, while that of compound IV completes within 72 h. This was probably

caused by the steric hindrances due to a large size of molecule of compound IV.
The epoxidation reaction proceeds without any participation of phosphazene ring,
31
since the P NMR spectrum of epoxidation product contain only the singlet peak
as was in starting compound IV (see Fig. 2,c).
Compound VI is a white brittle amorphous (according to the Smallangle X-
ray Scattering data) substance. There is no any kind of thermal effects on the DSC
curve up to the temperature of ~180 °C (see Fig. 3). After reaching this
temperature, an exothermic process was observed, which can be explained by the
destruction of substance, since the TGA curve confirmed the loss of mass at this
temperature.
Fig. 5. IR spectra of isophorone (A) diamine, (B) compound VI, and (C) the
resin based on them.

To evaluate the properties of compound VI as the epoxide resin, it was cured
by the treatment with isophorone diamine. Since compound VI was not softened
upon heating, it was impossible to prepare a composition via its direct mixing with
the curing agent. Thus, we decided to obtain the composition by mixing all the
components in a solution with the consequent evaporation of solvent. Thus, a
brown colored substance was obtained. The comparison of IR spectra of initial
components and obtained resin revealed the absence of peak at 1275 cm–1 in the
spectrum of resin, which was present in the case of compound VI (Fig. 5). This
peak is responsible for the symmetrical stretch vibrations of epoxy group.
This observation allowed us to conclude that all the epoxy groups were
involved in the reaction with diamine. In addition, the complete conversion was
also confirmed by a high content of gel-fraction (98%).
The obtained resin possess the glass transition temperature of 130 °C (see Fig.
3) and the decomposition temperature of 275 °C, which makes it promising for
practical applications.
Conclusions
This work have clearly demonstrated that the methallyl moiety can be
epoxidized more efficiently due to the electron-donor effect of methyl group. The
reaction between HCP and phenolate of 4-(2-(4-((β-methallyl)oxy)phenyl)propan-
2-yl)phenol can completely proceed only in high boiling solvents, which can well
solvates cations. It was also revealed that the Claisen rearrangement occurred at the
high temperature, and the complete epoxidation of double bonds in hexakis-4-(2-
(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene procceds
within 72 h. The resin based on the synthesized epoxide demonstrated promising
thermal characteristics, which allows it to be utilized in glue compositions.
Acknowledgements
The research is supported by the Ministry of Higher Education and Science of
The Russian Federation within the framework of state contract №14.583.21.0056.
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Highlights
Mono-β-methallyl ester of bisphenole A was synthesized.
The
reaction
between
mono-β-methallyl
ester
of
bisphenole
A
and
hexachlorocyclotriphosphazene was provided.
The double bonds in obtained aryloxyphosphazene was epoxidized with 3-chloroperbenzoic
acid.
The epoxidized aryloxyphosphazene was cured with isophorone diamine.