Synthesis of carboxylate phosphabetaines from 3-(diphenylphosphino)propanoic acid and unsaturated monocarboxylic acids

Article abstract of DOI:10.1134/S1070363215090042

Stable dicarboxylate phosphabetaines were synthesized by the phosphorylation of a series of unsaturated monocarboxylic acids (acrylic, crotonic, methacrylic, and cinnamic) with 3-(diphenylphosphino)-propanoic acid. The structure of the products was assessed by chemical, physical, and physicochemical methods. Alkylation of 3-(diphenylphosphino)propanoic acid with methyl iodide was studied for the first time to show that the reaction proceeds smoothly and yields the corresponding quaternary phosphonium salt.

Full text of DOI:10.1134/S1070363215090042

ISSN 1070-3632, Russian Journal of General Chemistry, 2015, Vol. 85, No. 9, pp. 2037–2041. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © Yu.V. Bakhtiyarova, R.R. Minnullin, I.V. Galkina, R.A. Cherkasov, V.I. Galkin, 2015, published in Zhurnal Obshchei Khimii, 2015,
Vol. 85, No. 9, pp. 1453–1458.
Synthesis of Carboxylate Phosphabetaines
from 3-(Diphenylphosphino)propanoic Acid
and Unsaturated Monocarboxylic Acids
Yu. V. Bakhtiyarova, R. R. Minnullin, I. V. Galkina, R. A. Cherkasov, and V. I. Galkin
Kazan (Volga) Federal University, ul. Kremlevskaya 18, Kazan, Tatarstan, 420008 Russia
e-mail: vig54@mail.ru
Received July 17, 2015
Abstract—Stable dicarboxylate phosphabetaines were synthesized by the phosphorylation of a series of
unsaturated monocarboxylic acids (acrylic, crotonic, methacrylic, and cinnamic) with 3-(diphenylphosphino)-
propanoic acid. The structure of the products was assessed by chemical, physical, and physicochemical
methods. Alkylation of 3-(diphenylphosphino)propanoic acid with methyl iodide was studied for the first time
to show that the reaction proceeds smoothly and yields the corresponding quaternary phosphonium salt.
Keywords: carboxylate phosphabetaines, unsaturated monocarboxylic acids, phosphonium salts
DOI: 10.1134/S1070363215090042
We previously described the syntheses of various
phosphabetaines from tertiary phosphines and unsatu-
rated mono- and dicarboxylic acids and the results of
their structural assessment and reactivity studies [1–10].
which is interesting in that it contains not only a tertiary
phosphorus atom, but also a carboxylic group (Scheme 1).
In our previous research on the kinetcs and mechanism
of reactions of tertiary phosphines with unsaturated
carboxylic acids in various reaction media we found
that the phosphorus quaternization process is solvent-
dependent and not always requires the third (proton-
donor) molecule to be involved [11–14]. It is interesting
to note that the carboxylic group of the substrate was
not involved in quaternization, and proton was
transferred either from the solvent or from the second
molecule of the unsaturated carboxylic acid (Scheme 2).
R1R2R3P + R4CH C COOH
R5
+
−
R1R2R3P CHCHCOO
R5
R4
R1 = R2 = R3 = Ph, Bu, C6H11; R4 = H, CH3, Ph, COOH;
R5 = H, CH3.
In the present work we set ourselves the task to
synthesize new stable dicarboxylate phosphabetaines
on the basis of unsaturated monocarboxylic acids. As a
tertiary phosphine phosphorylating agent we for the
first time used 3-(diphenylphosphino)propanoic acid
Scheme 2.
CH3
δ+
δ−
C
δ−
O
O
O
δ+
δ+
H
H
Scheme 1.
+
−
−
CR1
R2
Ph3P
R
C
3
δ
C
O
H2
C
P
C
H2
C OH
O
O
+
Ph3P CR1R2−CHR3
C
C CH3
O
O−
HO
2037

2038
BAKHTIYAROVA et al.
Scheme 3.
Ph
Ph
R3
+
P
C
H2C
Ph2PCH2CH2COOH + R C
C
COOH
H
R1
−
R1 R2
C
C COOH
OOC
R2
H
H
1−4
R1 = R2 = R3 = H (1); R1 = Me, R2 = R3 = H (2); R1 = R2 = H, R3 = Me (3); R1 = Ph, R2 = R3 = H (4).
Scheme 4.
O
Ph
Ph
+
P
Ph
Ph
OH
OH
−
CH2CH2COO
PH +
OOCH2CH2C
H
3
O
1
Consequently, we suggested that in the present case
the carboxyl proton of the phosphorylating agent,
namely, 3-(diphenylphosphino)propanoic acid, would
act as an additional proton donor.
is explained by the symmetry of the molecule with
respect to the phosphonium center and magnetic
equivalence of the carbon atoms.
It should be noted that dicarboxylate phospha-
betaine 1 was earlier prepared by Van Doorn and Wife
[15] by the reaction of diphenylphosphine and maleic
anhydride. In fact, the reaction involved maleic acid,
because the anhydride ring was opened with aqueous
alkali. Compound 1 was obtained in a 58% yield in
THF under reflux at the starting reagent ratio 1 : 3
(Scheme 4).
To check this suggestion, we reacted 3-(diphenyl-
phosphino)propanoic acid with a series of monocarp-
boxylic acids: acrylic, crotonic, methacrylic, and
cinnamic. The reactions all gave stable target products
1–4 (Scheme 3). The structure of these compounds
was proved by IR and 1Н, 31Р, and 13С spectroscopy, as
well as differential scanning calorimetry (DSC) and
thermo-gravimetry (TG). The composition of the
products was confirmed by their elemental analyses.
Obviously, at the first stage diphenylphosphine
adds by the С=С bond of maleic acid, after which
decarboxylation and formation of 3-(diphenylphos-
phino)propanoic acid, the starting tertiary phosphine in
our present work, take place. This phosphine then
reacts with the second maleic acid molecule also by
the С=С bond with analogous decarboxylation of the
α-carboxyl group of the intermediate to form dicar-
boxylate phosphabetaine 1. The third maleic acid
molecule is likely to act as an external proton donor, in
keeping with the above-described reaction mechanism.
The reaction of 3-(diphenylphosphino)propanoic
acid with acrylic acid smoothly occurs in ethyl acetate
(3–5 min) and acetonitrile (1 h).
Apparently, compound 1 has a symmetric structure
with respect to the phosphonium center. The IR
spectrum shows a single broad band near 1680 cm–1.
Consequently, the reaction product does not contain
the COOH group per se, which absorbs near 1600 cm–1.
Most likely, the negative charge is delocalized over
two carboxylic groups and, therefore, the only proton
is equally remote from the oxygen atoms of both
carboxyls.
The 13С NMR spectra of compounds 2–4 show two
doublet signals at 175–180 ppm (JCP = 12–17 Hz),
which, too, is evidence for the presence of two groups:
carboxyl and carboxylate. The spectrum of compound
1 contains only one doublet signal at 175 ppm, which
The spectral characteristics of betaine 1 obtained in
the present work are consistent with those in [15].
Thermogravimetry and differential scanning calori-
metry revealed a high thermal stability of phos-
phabetaine 1. The TG–DSC curve (see figure) shows a
well-defined endothermic effect with its maximum at
236°С, which is associated with a weight loss. The
decomposition of phosphabetaine 1 involves water and
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SYNTHESIS OF CARBOXYLATE PHOSPHABETAINES
DSC, mV/mg
2039
Ion current ×10–11, A
DTG, %/min
TG, %
exo
m/z 18
m/z 44
Temperature, °C
TG–DSC curve of phosphabetaine 1.
CO2 release. The absence of weight loss in the range
30–226°С is indicative of a high thermal stability of
this compound.
The structure of salt 5 was confirmed by 1Н and 13С
NMR spectrum. The 31Р NMR spectrum shows a
quaternary phosphorus signal at 24 ppm (Scheme 5).
The reactions of 3-(diphenylphosphino)propanoic
acid with crotonic, methacrylic, and cinnamic acids in
ethylacetate or acetonitrile are complete in 1 day and
form the target betaines 2–4 as white crystals in 67–
76% yields.
Of particular interest was alkylation of the very
phosphorylating agent, 3-(diphenylphosphino)propanoic
acid, with methyl iodide. This reaction gave the
corresponding phosphonium salt (2-carboxyethyl)-
(methyl)diphenylphosphonium iodide (6) in ≈80%
yield. The composition and structure of the product
were confirmed by elemental analysis and NMR and
IR spectroscopy (Scheme 6).
Previously we found [3–6] that structurally similar
phosphabetaines with various substituents at the phos-
phorus atom are easily alkylated with alkyl halides.
The composition and structure of the resulting phos-
phonium salts were confirmed by elemental analysis,
NMR and IR spectroscopy, and X-ray diffraction
analysis. In the present work we performed alkylation
of compound 1 with methyl iodide. The latter was also
used as a solvent, but because of the limited solubility
of the dicarboxylate phosphabetaine in it we had to add
a little ethanol to the reaction mixture. The reaction
proceeded at room temperature for 2 weeks and was
accompanied by decarboxylation, thus providing
indirect evidence showing that the starting compound
contains two carboxylic groups. The reaction gave
ethyl (3-methoxy-3-oxopropyl)diphenylphosphonium
iodide (5) in 82% yield.
Thus, the studied alkylation reactions make it
possible to attach various substituents to a tertiary phos-
phorus atom to obtain corresponding phosphonium
salts. Previously we showed [16] that the biological
activity of phosphonium salts increases with increasing
carbon chain length in the alkyl substituents (from 10
to 18 carbon atoms), such reactions provide great
scope for the synthesis of new biologically active
compounds.
Scheme 6.
Ph2PCH2CH2COOH + CH3I
Scheme 5.
+
+
I−
CH2CH2COOH
I−
I + CH3I
Ph2P
CH2CH2COOCH3
Ph2P
−CO2
Et
CH3
5
6
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 9 2015

2040
BAKHTIYAROVA et al.
(D2О): δP 33.48 ppm. Found, %: С 65.43; Н 5.34; Р
EXPERIEMENTAL
8.84. C19H21O4Р. Calculated, %: С 65.30; Н 5.50; Р 8.76.
1
The H, 13С, and 31Р NMR spectra (СDCl3) were
registered on a Bruker Avance-400 instrument. The IR
spectra were obtained on an IR Prestige-21 instrument
in the range 400–3700 cm–1 in mineral oil or in thin
film between KBr plates.
3-[(1-Carboxypropan-2-yl)diphenylphosphonium]-
propanoate (3) was prepared in a similar way from
0.5 g (0.0019 mol) of 3-(diphenylphosphino)propanoic
acid and 0.17 g (0.0020 mol) of methacrylic acid.
Yield 0.453 g (67.16%), white crystals, mp 79°С. IR
1
spectrum, ν, cm–1: 1620 (COO–), 1680 (COOH). H
Thermal stability was studied using a Netzsch
Jupiter STA 449C mictotermoanalyzer for smultaneous
thermogravimetric analysis and differential scanning
calorimetry, coupled with a Netzsch QMS 403C
Aeolos mass spectrometer; the samples were heated at
a rate of 10 deg/min in an argon atmosphere.
NMR spectrum (CDCl3), δ, ppm (J, Hz): 1.15 d.d (3H,
СH3, 4JРH 10.0, 3JHH 7.0), 2.37–2.49 m [1H, СН(СН3)],
2
3
2.54 d.d (2H, PСH2СН, JРH 15.0, JHH 5.5), 2.61 m
(2H, PСH2СH2), 3.28 m [2H, СH2С(О)], 7.49–7.74 m
(10H, Ar), 8.5 br.s (1Н, OH). 13С NMR spectrum
1
(CDCl3), δC, ppm (J, Hz): 17.56 d (PCH2CH2, JРС
3-[(2-Carboxyethyl)diphenylphosphonium]pro-
panoate (1). A solution of 0.08 g (0.0012 mol) of
acrylic acid in 3 mL of acetonitrile was added to a
solution of 0.3 g (0.0012 mol) of 3-(diphenylphos-
phino)propanoic acid in 5 mL of acetonitrile at room
temperature and continuous stirring. A white pre-
cipitate formed and was filtered off, washed many
times with diethyl ether, and dried in a vacuum. Yield
0.458 g (80.86%), white powder, mp 236°С. IR
spectrum, ν, cm–1: 1680 (COO–).1H NMR spectrum
(D2O), δ, ppm: 2.38–2.45 m [4H, СH2С(О)], 3.04–3.11
m (4H, PСH2), 7.57–7.76 m (10H, Ar). 13С NMR
2
52.0), 19.32 d (PCH2CH, JPC 9.0), 25.56 d (PCH2CH,
2
1JРС 51.0), 27.21 d (PCH2CH2, JРС 3.0), 34.8 (CH3),
1
2
116.51 d (Cipso, JРС 85.0), 129.99 d (Co, JPC 13.0),
3
4
132.86 d (Cm, JPC 10.0), 135.03 d (Cp, JPC 3.0),
3
3
172.80 d [С(О)О, JPC 3.7], 176.16 d [С(О)О, JPC
15.3]. 31P NMR spectrum (CDCl3): δP 27.1 ppm. Found,
%: С 69.48; Н 5.19; Р 7.76. C19H21O4Р. Calculated, %:
С 69.70; Н 5.13; Р 7.89.
3-[(2-Carboxy-2-phenylethyl)diphenylphospho-
nium]propanoate (4) was prepared in a similar way
from 0.3 g (0.0012 mol) of 3-(diphenylphosphino)
propanoic acid and 0.17 g (0.0012 mol) of cinnamic
acid. Yield 0.512 g (76.12%), white crystals, mp 193–
197°С. IR spectrum, ν, cm–1: 1590 (COO–), 1700
1
spectrum (D2О), δС, ppm (J, Hz): 16.73 d (PCH2, JРС
53.0), 27.28 d (PCH2CH2, JPC 3.0), 116.51 d (Cipso
,
2
1JРС 85.0), 129.99 d (Co, 2JPC 13.0), 132.86 d (Cm, JPC
3
10.0), 135.03 d (Cp, JPC 3.0), 175.87 d [C(O)O, JPC
4
3
1
(COOH). H NMR spectrum (D2O), δ, ppm (J, Hz):
31
2
14.5]. P NMR spectrum (D2О): δР 26.5 ppm. Found,
2.58 m (2H, PСH2СH2), 3.52 d.d (2H, PСHСН2, JРH
3
%: С 66.27; Н 5.50; Р 9.09. C18H19O4Р. Calculated, %:
С 65.45; Н 5.85; Р 9.39.
11.0, JHH 7.0), 3.44 m (2H, PСH2СH2), 3.61–3.72 m
(1H, PСН), 7.35–7.81 m (15H, Ar). 13С NMR spec-
trum (D2O), δC, ppm (J, Hz): 16.75 d (PCH2CH2),
3-[(2-Carboxypropyl)diphenylphosphonium]pro-
panoate (2) was prepared in a similar way from 0.5 g
(0.0019 mol) of 3-(diphenylphosphino)propanoic acid
and 0.17 g (0.0016 mol) of crotonic acid. Yield 0.496 g
(74.03%), colorless crystals, mp 176°С. IR spectrum,
2
27.03 d (PCH2CH2), 35.27 d (PCHCH2, JРC 9.0),
1
1
65.72 d (PCHCH2, JРC 61.0), 115.68 d (Cipso, JРС
5
4
84.0), 124.77 d (Cp, JPC 2.0), 127.18 d (Cm, JPC 3.0),
128.34 d (Co, JPC 7.0), 129.95 d (Co, JPC 13.0),
3
2
132.54 d (Cm, JPC 10.0), 134.87 d (Cp, JPC 2.0),
3
4
ν, cm–1: 1630 s (COO–), 1710 s (COOH). H NMR
1
135.13 d (Cipso, JРС 10), 174.50 d [С(О)О, JРC 12.0],
2
3
spectrum (D2O), δ, ppm (J, Hz): 1.09–1.16 d.d (3H,
3
177.16 d [С(О)О, JРC 15.0]. 31P NMR spectrum
3
3
СH3, JРH 18.5, JHH 7.0), 1.9–1.99 m (2H, PСH2),
2.29–2.43 m (1H, PСH), 2.56– 2.68 m (2H, PСНСH2),
3.00–3.07 m (2H, PСН2СH2), 7.38–7.76 m (10H, Ar).
13С NMR spectrum (D2О), δС, ppm (J, Hz): 12.5 d
(H2O): δP 30.77 ppm. Found, %: С 70.1; Н 5.34; Р
7.94. C19H21O4Р. Calculated, %: С 70.4; Н 5.66; Р 7.64.
Ethyl(3-methoxy-3-oxopropyl)diphenylphospho-
nium iodide (5). Methyl iodide, 0.07 mL (0.0012 mol)
was added to a solution of 0.4 g (0.0012 mol) of
betaine 1 in 1.5 mL of ethanol. The reaction mixture
was leave to stand at room temperature for 2 weeks.
The solvent was removed in a vacuum. The residue
2
1
(СНСН3, JCР 2.0), 15.96 d (РСН2, JCР 52.0), 23.56 d
1
2
(РСНСН3, JCР 72.0), 26.30 d (РСН2СН2, JCР 3.0),
27.05 d (РСНСН2,2JCР 3.0), 114.26 d (Cipso, 1JCР 84.0),
129.75 d (Co, JCР 12.0), 130.08 d (Cm, JCР 11.0),
2
3
132.93 d (Cp, JCР 3.0), 175.3 d [С(О)О, JCР 17.0],
4
3
176.42 d [С(О)О, JCР 15.0]. 31P NMR spectrum
3
1
was an oily substance. H NMR spectrum (СDCl3), δ,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 9 2015

SYNTHESIS OF CARBOXYLATE PHOSPHABETAINES
2041
4. Galkin, V.I., Bakhtiyarova, Yu.V., Polezhaeva, N.A.,
Galkina, I.V., Cherkasov, R.A., Krivolapov, D.B.,
Gubaidullin, A.T., and Litvinov, I.A., Russ. J. Gen.
Chem., 2002, vol. 72, no. 3, p. 384. DOI: 10.1023/
A:1015487416152.
5. Galkin, V.I., Bakhtiyarova, Yu.V., Sagdieva R.I.,
Galkina, I.V., Cherkasov, R.A., Krivolapov, D.B.,
Gubaidullin, A.T., and Litvinov, I.A., Russ. J. Gen.
Chem., 2006, vol. 76, no. 3, p. 430. DOI: 10.1134/
S1070363206030133.
6. Galkin, V.I., Bakhtiyarova, Yu.V., Sagdieva, R.I.,
Galkina, I.V., and Cherkasov, R.A., Heteroatom.
Chem., 2006, vol. 17, p. 557. DOI: 10.1002/hc.20276.
7. Bakhtiyarova, Yu.V., Sagdieva, R.I., Galkina, I.V.,
Galkin, V.I., Cherkasov, R.A., Krivolapov, D.B.,
Gubaidullin, A.T., and Litvinov, I.A., Russ. J. Org.
Chem., 2007, vol. 43, no. 2, p. 207. DOI: 10.1134/
S1070428007020091.
ppm (J, Hz): 1.14 m (3H, PСH2CH3), 2.18 s [3H, ОCH3),
2.71 m (2H, PСH2CH2), 3.55 m (2H, PСH2CH3), 3.97
m [2H, СH2С(О)], 7.65–7.87 m (10H, Ar). 13С NMR
spectrum (D2О), δС, ppm (J, Hz): 14.05 d (PCH2CH3,
1
2JPC 2.0), 18.14 d (PCH2CH3, JPC 43.0), 18.39 d
1
2
(PCH2CH2, JPC 53.0), 27.17 d (PCH2CH2, JPC 2.7),
61.81 (ОСН3), 116.51 d (Cipso, 1JРС 84.0), 130.58 d (Cо,
2JPC 20.0), 133.41 d (Cm, JPC 9.0), 135.29 d (Cп, JPC
3
4
2.0), 170.62 d [С(О)О, JРC 8.0]. 31Р NMR spectrum
3
(Н2О): δР 27.37 ppm
(2-Carboxyethyl)(methyl)diphenylphosphonium
iodide (6). Methyl iodide, 0.17 mL (0.0019 mol), was
added to a solution of 0.5 g (0.0019 mol) of 3-(di-
phenylphosphino)propanoic acid in 1.5 mL of aceto-
nitrile. The reaction mixture was leave to stand at room
temperature for 1 week. The solvent was removed in a
vacuum, and the residue was washed with diethyl ether
and dried in a vacuum. Yield 0.605 g (79.6%), mp
138°С. 1H NMR spectrum (D2O), δ, ppm (J, Hz): 2.42
8. Galkin, V.I., Mal’tsev, D.B., Sobanov, A.A., Goro-
khov, V.L., and Bakhtiyarova, Yu.V., Uchen. Zapiski
Kazan. Univ. Estestv. Nauki, 2006, vol. 148, no. 4, p. 8.
1
d (3H, PСH3, JPH 13.9), 2.54–2.61 m (2H, PСH2),
9. Bakhtiyarova, Yu.V., Bondar’, M.S., Galkina, I.V., and
Galkin, V.I., Uchen. Zapiski Kazan. Univ. Estestv.
Nauki, 2008, vol. 150, no. 1, p. 42.
3.06–3.13 m [2Н, СH2С(О)], 7.55–7.73 m (10H, Ar).
13С NMR spectrum (D2О), δС, ppm (J, Hz): 6.00 d
1
1
(PСH3, JРС 56.3), 18.00 d (PСH2, JРС 55.5), 26.40 d
[СH2С(О), 2JPC 1.4], 118.40 d (Ph, 1JРС 88.4), 129.92 d
(Ph, 2JPC 12.6), 132.19 d (Ph, 3JPC3 10.5), 134.86 d (Ph,
4JPC 3.0), 174.63 d [C(O)OH, JPC 14.0]. 31P NMR
spectrum (Н2О): δР 23.49 ppm.
10. Galkin, V.I., Salin, A.V., Bakhtiyarova, Yu.V., and
Sobanov, A.A., Russ. J. Gen. Chem., 2009, vol. 79,
no. 5, p. 919. DOI: 10.1134/S1070363209050090.
11. Salin, A.V., Sobanov, A.A., Bakhtiyarova, Yu.V.,
Khabibullin A.A., and Galkin, V.I., Russ. J. Gen.
Chem., 2010, vol. 80, no. 9, p. 1738. DOI: 10.1134/
S1070363210090033.
ACKNOWLEDGMENTS
12. Salin, A.V., Sobanov, A.A., Bakhtiyarova, Yu.V., Kha-
bibullin, A.A., Galkin, V.I., and Cherkasov, R.A.,
Phosphorus, Sulfur, Silicon, Relat. Elem., 2011, vol. 186,
no. 4, p. 854. DOI: 10.1080/10426507.2010.500642.
The work was funded by the grant from the
Government of the Russian Federation to the Kazan
Federal University for scientific research.
13. Salin, A.V., Sobanov, A.A., Bakhtiyarova, Yu.V.,
Khabibullin, A.A., Galkin, V.I., and Cherkasov, R.A.,
Phosphorus, Sulfur, Silicon, Relat. Elem., 2011, vol. 186,
no. 4, p. 857. DOI: 10.1080/10426507.2010.500643.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 9 2015