Interfacial synthesis of bisphenol A tetrachlorocyclotriphosphazene from bisphenol A and hexachlorocyclotriphosphazene

Article abstract of DOI:10.1016/j.tetlet.2013.07.098

The effect of solvent purity on the synthesis and yield of bisphenol A tetrachlorocyclotriphosphazene (BATCCP) has not been described in the literature. The purpose of this research was to synthesize BATCCP hybrid monomers and to evaluate the effect of solvent purity on the BATCCP production. BATCCP monomers were prepared by an interfacial procedure in a water/toluene system as a function of time with the assistance of a phase transfer catalyst, tetraoctylammonium bromide. ¹H and ³¹P NMR confirmed the production of BATCCP monomer by the appearance of chemical shifts at 7.18 and 5.35 ppm in the ¹H NMR and 23.4 and 13.9 ppm in the ³¹P NMR, respectively. Distillation of the toluene, not suggested in previous reports of HCCP hybrid synthesis, resulted in an improvement of actual % yield to 40% and stability of the product throughout the 1440 min reaction as confirmed by MALDI, compared with an 11% actual yield at 15 min, decaying to 2% over a 1440 min reaction when the synthesis was performed with 'anhydrous toluene' as provided commercially without further distillation.

Full text of DOI:10.1016/j.tetlet.2013.07.098

Tetrahedron Letters 54 (2013) 5311–5313
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Interfacial synthesis of bisphenol A tetrachlorocyclotriphosphazene
from bisphenol A and hexachlorocyclotriphosphazene
Tiffany N. Thompson a, , Susan Ramos-Hunter a,b, Jasmine Robertson a, Natalie Y. Arnett a,b
⇑
a Fisk University, Department of Life and Physical Sciences, 1000 17th Ave. N., Nashville, TN 37208, USA
b Vanderbilt University, Department of Chemistry, 7330 Stevenson Center, Station B 351822, Nashville, TN 37235, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The effect of solvent purity on the synthesis and yield of bisphenol A tetrachlorocyclotriphosphazene
(BATCCP) has not been described in the literature. The purpose of this research was to synthesize BATCCP
hybrid monomers and to evaluate the effect of solvent purity on the BATCCP production. BATCCP mono-
mers were prepared by an interfacial procedure in a water/toluene system as a function of time with the
assistance of a phase transfer catalyst, tetraoctylammonium bromide. 1H and 31P NMR confirmed the pro-
duction of BATCCP monomer by the appearance of chemical shifts at 7.18 and 5.35 ppm in the 1H NMR
and 23.4 and 13.9 ppm in the 31P NMR, respectively. Distillation of the toluene, not suggested in previous
reports of HCCP hybrid synthesis, resulted in an improvement of actual % yield to 40% and stability of the
product throughout the 1440 min reaction as confirmed by MALDI, compared with an 11% actual yield at
15 min, decaying to 2% over a 1440 min reaction when the synthesis was performed with ‘anhydrous tol-
uene’ as provided commercially without further distillation.
Received 21 May 2013
Revised 16 July 2013
Accepted 18 July 2013
Available online 26 July 2013
Keywords:
Interfacial synthesis
Poly(arylene ether sulfone)
Hexachlorocyclotriphosphazene
Proton exchange membrane
Phosphonitrilic chloride trimer
Published by Elsevier Ltd.
Introduction
one-to-six of its component chlorine groups. The present study re-
ports the successful incorporation of the nucleophile bisphenol A
Sulfonated poly(arylene ether sulfone)s (PAES) are stable ion-
conducting polymers used in fuel cell and reverse osmosis mem-
branes. Current PAES polymers are the product of co-polymeriza-
into a hybrid monomer, bisphenol A tetrachlorocyclotriphospha-
zene (BATCCP). BATCCP monomers could serve as a pathway to
the synthesis of BATCCP PAES-XX hybrid copolymers for use as
proton exchange membranes in fuel cells.
tion of
a sulfonated dichlorodiphenylsulfone (SDCDPS) and
dichlorodiphenylsulfone (DCDPS) linked together with one of the
varieties of bi-functional aryloxy groups, for example, bisphenol A
(Bis A).1–5 Higher degrees of sulfonation (above 50%) of PAES poly-
mers lead to mechanical instability and excessive swelling of the
fuel cell proton exchange membrane.6,7 The generic PAES backbones
do not allow for crosslinking or other post-modifications that would
permit enhancement of polymer properties for different applica-
tions. As a result, chemical or physical crosslinking ionomers have
been widely pursued in an effort to overcome the problems with
swelling and mechanical stability in these polymers.8 We postulate
that one strategy for achieving variable PAES-based polymers would
be to modify polymer synthesis so that bisphenol A or other aryl
groups are introduced as a hybrid monomer with compounds that
would introduce side chains for variable post-modifications. One
such hybrid monomer would be bisphenol A conjugation with hexa-
chlorocyclotriphosphazene (HCCP).
Previous studies describing the synthesis of BATCCP have been
reported.9,10 However, documentation to verify BATCCP formation
was not given. Kumar9 reported the synthesis of nucleophilic
arrangements of HCCP with a number of phenolic compounds,
including bisphenols in toluene as a single phase reaction. Utiliza-
tion of the same synthetic route in our laboratory yielded a mix-
ture of unreacted Bis A, mono-substituted and di-substituted
BATCCP products. Wu and Meng10 used a phase transfer catalyst
(PTC) in an interfacial reaction to transport the catalyzed interme-
diate, phenyloxy, into an organic layer containing HCCP. Though
NMR analysis was employed to monitor the formation of stereoiso-
mers (geminal and nongeminal formations) during the reaction, no
spectra were provided to confirm the formation of the putative
products.
In the present study, BATCCP monomers were prepared interfa-
cially using phase transfer catalysis in an immiscible solvent sys-
tem of water and toluene. Analysis by NMR and MALDI
confirmed the successful synthesis of the BATCCP hybrid mono-
mer. During the course of our studies, we identified the importance
of toluene solvent purity on both the rate and extent of product
formation.
HCCP, a cyclic trimer of phosphonitrilic chloride, can form reac-
tive cyclotriphosphazenes (CTPs) by nucleophilic substitution of
⇑
Corresponding author. Tel.: +1 615 329 8780; fax: +1 615 329 8577.
E-mail address: tiffany.thompson064@gmail.com (T.N. Thompson).
0040-4039/$ - see front matter Published by Elsevier Ltd.
http://dx.doi.org/10.1016/j.tetlet.2013.07.098

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T. N. Thompson et al. / Tetrahedron Letters 54 (2013) 5311–5313
Results and discussion
1H NMR analysis of our synthetic product, shown in Figure 1, is
consistent with the formation of a Bisphenol–HCCP adduct. The
occurrence of the peak at 7.18 ppm (label ‘f’ on spectrum) indicates
the successful formation of a P–O bond between HCCP and Bis A to
make BATCCP. The presence of the peak at 7.18 ppm arises due to
the change in chemical environment of the proton on the aromatic
ring closest to the oxygen (‘f’ on BATCCP structure) from the loss of
the phenolic proton to form the P–O bond with HCCP. The phenolic
(O–H) proton at 5.35 ppm (‘a’ on spectrum and BATCCP structure)
also indicated the successful synthesis of BATCCP. Peaks due to the
presence of the phase transfer catalyst (TOABr) were observed at
ꢀ0.1, 0.9, 1.25, and 2.1 ppm.
31P NMR also supports the 1H NMR data confirming the success-
ful synthesis of BATCCP in the current study (Fig. 2). The triplet at
13.9 ppm is indicative of the phosphorous with two chlorine atoms
attached (‘a’ on structure) while the doublet at 23.4 ppm (‘b’ on
structure) is that of the phosphorous bonded to a chlorine atom
and a bisphenol A molecule, as previously predicted. 31P NMR
chemical shifts also were observed at 16.5 and 25.7 ppm, corre-
sponding to predicted shifts for the mono-substituted side product,
bisphenol A pentachlorocyclotriphosphazene (BAPCCP).
To optimize conditions to attain the highest yield of the desired
BATCCP product, products achieved at 15, 120, 240, and 1440 min
in reactions using distilled or undistilled toluene as solvent were
analyzed by matrix-assisted laser desorption/ionization (MALDI).
Figure 3 provides a MALDI spectrum for a 1440 min reaction using
Figure 3. MALDI analysis of the products of the hybrid monomer interfacial
synthetic reaction using distilled versus undistilled toluene as the organic phase.
MALDI spectrum at 1440 min for synthesis with distilled toluene (a) and undistilled
toluene (b). The predicted molecular weights for di-substituted BATCCP, the desired
product, and mono-substituted BAPCCP are approximately 729 and 539 m/z,
respectively. The product yield for each time point in distilled and undistilled
toluene, using MALDI, is tabulated in (c). Calculations to determine the isolated
yield (%), fractional (%), and actual BATCCP (%) yield can be found in the
Supplementary data section.
distilled toluene (a) and undistilled toluene (b) as solvent; data
from all time points assessed (tabulated in Fig. 3c) reveal that a
higher % yield (40%) was obtained at 1440 min (24 h) for reactions
conducted in distilled toluene. Since BAPCCP serves as the mono-
substituted precursor for the desired di-substituted BATCCP prod-
uct, the data in the presence of distilled toluene are as expected: as
the BAPCCP decreases in fractional percent, that for BATCCP in-
creases. In contrast, in undistilled toluene, the percent yield of
BATCCP is trivial, due in large part to hydrolysis of the HCCP start-
ing material and formation of HCCP dimers (cf. Fig. 3b), thus also
explaining the unexpected BAPCCP precursor–BATCCP product
relationship.
Figure 1. 1H NMR of BATCCP product. The letters indicate the chemical shifts
corresponding to those in the BATCCP structure.
Conclusion
Cl
Cl
BATCCP was successfully synthesized by an interfacial synthesis
through the use of a PTC. The product was confirmed through 1H
NMR, 31P NMR, and MALDI. The presence of the mono-substituted
side product (BAPCCP) was also observed and was easily removed
by purification. Preliminary research indicated that distilling the
anhydrous toluene prior to the reaction has a large effect on the
experimental outcome. Reactions carried out in distilled anhy-
drous toluene produced a higher actual % yield of BATCCP with a
maximum yield of 40% after 1440 min of reaction.
a
P
N
P
N
P
Cl
Cl
b
b
N
O
OH
HO
O
Acknowledgments
These studies were supported by NSF HRD-1137573, NSF-
CREST-CA, HRD-0420516 at Fisk University; NFS-STC CLiPS-
0423914, and Quality Education for Minorities (QEM) Network
32432925001. Instrumentation at Vanderbilt was supported by
Figure 2. 31P NMR of BATCCP product. The letters indicate the chemical shifts
corresponding to those in the BATCCP structure.

T. N. Thompson et al. / Tetrahedron Letters 54 (2013) 5311–5313
5313
NSF HRD-1110924 AGEP. NMR and MALDI analysis was performed
References and notes
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studies involving HCCP in tetrahydrofuran; V. Anyaeche, D. Garcia,
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Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.tetlet.2013.
07.098.