Tri-n-butylphosphine-Catalyzed Phosphonoethylation Reactions of Hydrophosphoryl Compounds

Article abstract of DOI:10.1134/S1070363219110070

An efficient method for the synthesis of 1,2-bisphosphoryl compounds based on the addition of hydrophosphoryl derivatives to O,O-diethyl vinylphosphonate was developed. The reaction proceeds in mild conditions under catalysis with tri-n-butylphosphine and leads to the formation of the corresponding target products with high yield.

Full text of DOI:10.1134/S1070363219110070

ISSN 1070-3632, Russian Journal of General Chemistry, 2019, Vol. 89, No. 11, pp. 2207–2211. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Zhurnal Obshchei Khimii, 2019, Vol. 89, No. 11, pp. 1686–1691.
Tri-n-butylphosphine-Catalyzed Phosphonoethylation Reactions
of Hydrophosphoryl Compounds
A. V. Il’ina,*, A. A. Antonovaa, N. G. Khusainovaa, and V. I. Galkina
a Kazan (Volga Region) Federal University, Kazan, 420008 Russia
* e-mail: antonilin.1989@mail.ru
Received April 29, 2019; revised April 29, 2019; accepted May 16, 2019
Abstract―An efficient method for the synthesis of 1,2-bisphosphoryl compounds based on the addition of hydro-
phosphoryl derivatives to O,O-diethyl vinylphosphonate was developed. The reaction proceeds in mild conditions
under catalysis with tri-n-butylphosphine and leads to the formation of the corresponding target products with
high yield.
Keywords: phosphine-catalyzed reactions, bisphosphonates, bisphosphine oxides, phosphonoethylation, hydro-
phosphoryl compounds, vinylphosphonates
DOI: 10.1134/S1070363219110070
1,2-Bisphosphoryl compounds—vicinal bisphospho-
nates and bisphosphine oxides—have been widely used as
ligands in complexes of transition elements [1, 2]. Vicinal
bisphosphonates, and also their 99mTc complexes can be
used as markers in obtaining images of tumors and their
further treatment [3, 4]. Vicinal bisphosphine oxides are
successfully used to synthesize coordination polymers
[5]; complexes with neptunium [6], tungsten [7], and
yttrium [8] were obtained on the basis of the 1,2-(bisdi-
enilylphosphoryl)ethane fragment. The high phosphorus
content in 1,2-bisphosphoryl compounds makes it pos-
sible to use them as antipyrenes [9–11].
nickel [21], and rhodium in the microwave radiation [22]
were proposed for obtaining 1,2-bisphosphonates and
bisphosphine oxides.
Bis(diphenylphosphino)ethane dioxide can be ob-
tained by the reaction of diphenylphosphine oxide with
α-chloroacryl acid in a superbasic medium accordin to
the addition-decarboxylation scheme [23].
In contrast to the above methods, in which two identi-
cal phosphorus fragments are introduced, the method of
phosphorylation of vinylphosphonates is able to produce
compounds with different substitutes at the phosphorus
atom. One of the main methods of hydrophosphorylation
of vinylphosphonates in the presence of alkaline metals
alkoxides was described by A.N. Pudovik in 1953 and
is called the reaction of phosphonoethylation, similar to
the reaction of cyanoethylation [24]. A similar process
was also described in the USA patent in 1962 [25]. Hy-
drophosphoryl compounds are also added at the double
bond of vinylphosphonates when heated in the presence
of oxygen [26], microwave radiation [27], and trimeth-
ylphosphine in the inert atmosphere [28, 29].
In light of the considerable practical interest in various
derivatives of bisphosphonates and bisphosphine oxides,
intensivesearchisunderwayfornewhighlyeffectivemeth-
ods of their synthesis. Bisphosphine oxides are obtained
by the oxidation of relevant bisphosphines in various con-
ditions [10, 12].Another method is the reaction of 1,2-di-
halide derivatives with trialkyl phosphites (Arbuzov’s
reaction) [13–17]. The reactions characterized by low
yields of the target disubstituted product and require high
temperature. Vicinal bisphosphonates and bisphosphine
oxides can be obtained from digalide derivatives by reac-
tions with hydrophosphoric compounds [18, 19].
In order to develop methods for obtaining 1,2-
bisphosphoryl compounds of practical significance, we
investigated reactions of O,O-diethylvinylphosphonate
with some hydrophosphoryl compounds in the presence
of tri-n-butylphosphine as a catalyst (Scheme 1). We
have previously shown that tri-n-butylphosphine is an
Methods for obtaining bisphosphoryl compounds on
the base of alkynes have been developed. Thus, reac-
tions of alkynes with hydrophosphoric compounds in
the presence of organometallic catalysts palladium [20],
2207

2208
IL’IN et al.
Scheme 1.
R
R
O
R
R
O
H
O
30 mol % PBu3
MeCN, 20°C
O
P
P
+
P
P
EtO
EtO
OEt
OEt
1–3
R = OEt (1), OMe (2), Ph (3).
effective catalyst for hydrophosphorylation reactions of
alkenes and alkynes activated by electron-acceptor groups
[30–32]. At the same time, it is worth noting that all the
reactions occur with high yields at room temperature.
Reactions using tri-n-butylphosphine were found to
require no inert atmosphere (unlike trimethylphosphine)
and could be carried out using commercially available
solvents without prior preparation. At the same time, the
phosphine oxidation during the reaction is negligible.
findings [28] for tetrahydrofurane. However, with the
increase in the catalyst concentration up to 30%, it was
possible to achieve a moderate yield of the target com-
pound within the same time (see the table). The maximal
yield was reached within 3 h. Further increase in reaction
time or catalyst concentration had insignificant effect on
the target bisphosphonate yield.
Less nucleophilic tryphenylphosphine did not catalyze
this reaction. The use of the closest analogues of phos-
phines, tertiary amine, namely triethyalmine and more
nucleophilic 1,4-diazabicyclo[2.2.2]octane (DABCO),
also did not result in obtaining the target reaction product
(see the table).
The reactions were carried out in conditions, which we
had previously optimized for phosphine-catalyzed hydro-
phosphorylation of acrylic and metacrylic acids deriva-
tives [32]. Polar solvents favor the phosphine-catalyzed
hydrophosphorylation, the best results were shown when
using acetonitrile. This solvent has been recommended
on the basis of previous kinetic studies concerning the
quaternization of tertiary phosphines by electron deficient
alkenes. It turned out that when 5% PBu3 in acetonitrile
was used, only trace amounts of the target product were
observed after1 h. These data are also consistent with the
Reactions involving dimethyl phosphite proceeded
smoothly under the same conditions to give the hydro-
phosphorylation product with a high yield.
Unlike the reactions of dialkyl phosphites, the reac-
tion with diphenylphosphine oxide resulted in the high
conversion into the product even within 1 h (see the table).
This was not unexpected for us, as the greater reactivity
of diarylphosphine oxides compared to dialkyl phosphites
has been discussed before [34, 35].
Optimization of conditions and yield of products in the
reactions of hydrophosphoryl compounds with O,O-diethyl-
vinylphosphonate
Based on the data obtained, a possible mechanism of
the phosphine-catalyzed O,O-diethylvinylphosphonite
hydrophosphorylation is presented in Scheme 2.
Conversiona, % (catalyst
R
Time, h
Yieldb, %
amount, mol %)
Traces (5 mol % PBu3)
Traces (5 mol % PBu3)
63 (30 mol % PBu3)
EtO
1
3
1
–
–
–
As with other phosphine-catalyzed reactions, the
first stage of this reaction is the nucleophilic attack of
the electrophilic C=C bond by tributylphospine, which
leads to the formation of zwitter-ion intermediate A [36].
The resulting anionic center deprotonates the hydro-
phosphoryl compound. Obviously, at this stage the more
acidic trivalent three-coordinated tautomeric form of the
hydrophosphoryl compound takes part. The higher reac-
tivity of diphenylphosphine oxide compared to dialkyl
phosphites in this case may be associated with the easier
formation of the tautomeric trivalent three-coordinated
form, which also follows from the published data on the
study of tautomeric transformations of hydrophosphoryl
compounds [37]. The resulting anion C is further in-
volved in the reaction with another vinyl-phosphonate
3
3
3
3
92 (30 mol % PBu3)
0 (30 mol % PPh3)
0 (30 mol % NEt3)
0 (30 mol % DABCO)
85
–
–
–
MeO
Ph
1
3
1
3
60 (30 mol % PBu3)
88 (30 mol % PBu3)
95 (30 mol % PBu3)
95(30 mol % PBu3)
–
82
92
–
а According to 31P NMR data. b Pure compound yield.
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TRI-n-BUTYLPHOSPHINE-CATALYZED PHOSPHONOETHYLATION REACTIONS
2209
Scheme 2.
O
+
O
R1
R2
–
Bu3P
O
+
PBu3
P
P
P
P
P
OH
OEt
OEt
OEt
OEt
R1
H
R2
+
+
–
Bu3P
OH
OEt
Bu3P
O
P
OEt
OEt
OEt
OEt
+
A
Bu3P
O
P
R1
P
O
OEt
R1
R2
B
R2
EWG
–
O
P
E
C
R1
EWG
P
OH
R2
+
R1
R2
Bu3P
OH
O
–
P
P
O
OEt
OEt
O
P
P
EtO
OEt
+
Bu3P
P
R1
R2
O
–
O
P
OEt
OEt
B
EtO
OEt
D
molecule to give anion D. This anion deprotonates the
next molecule of the hydrophosphoryl compound to form
the target bisphosphoryl compound and anion C, which
is re-involved in the reaction with the unsaturated deriva-
tive, thus continuing the catalytic cycle.
range of 4000 to 450 cm–1. Mass spectra were recorded on
anAB Sciex Triple TOF 5600 high-resolution quadrupole
time-of-flight mass spectrometer. The mass spectra were
recorded with the turboion spray ionization of solutions
of substances in methanol with positive polarity of ions.
It is most likely that the dependence of the product
yield on the catalyst concentration is caused by the in-
crease in the zwitter-ionic intermediate concentration,
which was favored by an increase in the tertiary phosphine
amount in the mixture.
General procedure of phosphine-catalyzed hydro-
phosphorylation of O,O-dietylvinylphosphonate. To a
solution of 0.004 mol of a hydrophosphoryl compound
in 3 mL of acetonitrile and 30 mL of tributylphosphine,
a solution of 0.004 mol of O,O-dietylvinylphosphonate
in 7 mL of acetonitrile was added dropwise within
15 min with continuous stirring and cooling. The reaction
mixture was kept in a water bath for 3 h. The reaction
completeness was controlled by the 31P NMR spectros-
copy. At the end of the reaction, the solvent was driven
away at low pressure; the target product was isolated and
purified according to one of the presented procedures
(depending on the product aggregate state). Liquid prod-
ucts were isolated by vacuum distillation, during which
low-boiling tributylphophine (which can be multiply used
as a catalyst in the reaction) and the target product was
separated as a high-boiling fraction. The crystalline prod-
The composition and structure of the resulting
bisphosphoryl compounds were determined by a combi-
nation of physical research methods.
EXPERIMENTAL
The NMR spectra were recorded on a Bruker Avance
III 400 instrument [400 (1Н), 161.9 (31Р{1H}), 100.6 MHz
(13С{1H})] in CDCl3 solution relative to tetramethylsilane
13
31
as an internal standard (1H and C). For the P NMR
spectra 85% H3PO4 was used as an external standard.
The IR spectra were recorded on a Spectrum two Perkin-
Elmer device using an UATR Sampling surfaces in the
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 89 No. 11 2019

2210
IL’IN et al.
uct of diphenylphosphine oxide addition was completely
crystallized upon the acetonitrile vaporization at low pres-
sure. The resulting powder was washed with pentane and
diethyl ether, filtered off, and dried at low pressure for
6 h. Tributylphosphine was regenerated from pentane and
ether solution by distillation.
(calculated for C18H25O4P2: 367.1228). Physical con-
stants and spectral data coincide with those previously
described for this compound [27].
FUNDING
The work was financially supported by the Russian Fund for
Fundamental Research (project no. 18-33-00047) and a grant
given to Kazan Federal University to perform a state task in
the field of scientific research (no. 4.5888.2017/8.9).
Tetraethylethane-1,2-dialphosphonate (1). Yield
85%, colorless liquid, bp 218°С(1.5 mmHg). IR spectrum,
ν, cm–1: 1243 s (P=О), 1020 s (P–О–С). 1Н NMR spec-
trum, δ, ppm: 1.31 t (12Н, POCH2CH3, 3JНН = 7.1 Hz),
1.92–1.99 m (4Н, PCH2), 4.04–4.17 m (8Н, PОСH2).
13С{1H} NMR spectrum, δС, ppm: 16.5 (PОСН2СН3),
17.9–20.1 m (PCH2), 61.8 (PОСН2СН3). 31P{1H} NMR
spectrum, δР, ppm: 29.4. Mass spectrum (ESI), m/z:
303.1126 [М + H] (calculated for C10H25O6P2: 303.1126).
Physical constants and spectral data coincide with those
earlier described for this compound [38].
CONFLICT OF INTEREST
No conflict of interest was declared by the authors.
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