The use of a diammonium salt in the synthesis of organic carbonates from epoxides and CO2: promoting effect of support

Article abstract of DOI:10.1007/s11172-020-2869-5

Onium salt, N¹, N¹, N¹, N⁵, N⁵, N⁵-hexaethylpentane-1,5-diammonium dibromide, was used as a catalyst for the addition of CO₂ to epoxides. An influence of insoluble supports on the rate of the process as well as possibility of recycling of the catalytic system are described. In addition, the effects of temperature and CO₂ pressure on the yields of products are discussed.

Full text of DOI:10.1007/s11172-020-2869-5

Russian Chemical Bulletin, International Edition, Vol. 69, No. 6, pp. 1076—1079, June, 2020
1076
The use of a diammonium salt in the synthesis of organic carbonates
from epoxides and CO2: promoting effect of support*
S. E. Lyubimov,а A. A. Zvinchuk,а V. A. Davankov,a B. Chowdhury,b A. V. Arzumanyan,a and A. M. Muzafarova
аA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 6471. E-mail: lssp452@mail.ru
bDepartment of Chemistry Indian Institute of Technology (Indian School of Mines),
826004 Dhanbad, India. E-mail: biswajit72@iitism.ac.in**
Onium salt, N1,N1,N1,N5,N5,N5-hexaethylpentane-1,5-diammonium dibromide, was used
as a catalyst for the addition of CO2 to epoxides. An influence of insoluble supports on the rate
of the process as well as possibility of recycling of the catalytic system are described. In addition,
the effects of temperature and CO2 pressure on the yields of products are discussed.
Key words: diammonium salt, carbon dioxide fixation, epoxides, cyclic carbonates, cata-
lytic support.
Carbon dioxide is of great interest for use in various
reactions and processes due to its availability, low cost,
renewability, incombustibility, and safety compared to
many other gases.1 In addition, the possibility of its use is
a direct solution to the environmental problem associated
with an increasing excess of CO2 in nature due to wide-
spread consumption of raw materials.2 One of the effective
and practical directions for using CO2 is its addition at
-epoxides with the formation of organic carbonates.3,4
The products of this reaction are widely used as fuel addi-
tives, electrolytes for lithium-ion batteries, polar solvents,
anti-caking agents, monomers for the production of poly-
carbonates and polyurethanes.5 Various catalysts including
complexes of transition and non-transition metals, de-
rivatives of Sc, Sm, Y, La, Re, modified carbon nanotubes,
complexes of crown ethers, modified molecular sieves,
ionic liquids based on ammonium, imidazolium, and
phosphonium salts, as well as a number of other com-
pounds have been tested for this reaction at present.6 The
development of catalytic systems that combine low cost,
the ability to work at low temperatures and low CO2 pres-
sures, the possibility of easy separation from reaction
products, and repeated use is of considerable interest today.
In this work, the use of readily available diammonium
salt as a catalyst for the reaction of CO2 addition to ep-
oxides is considered. Positive effect of using a number of
supports on the conversion in this reaction is described.
The effect of temperature and CO2 pressure on the yield
of products is studied, and the possibility of recycling of
this available catalyst system is demonstrated.
Results and Discussion
Quaternization of triethylamine with 1,5-dibromopen-
tane (110 °C, 24 h) yielded N1,N1,N1,N5,N5,N5-hexa-
ethylpentane-1,5-diamonium dibromide (1, Scheme 1).
Note that this approach does not include the use of a sol-
vent and is faster in comparison with other methods known
in the literature.7—9
Scheme 1
Preliminary testing of diammonium salt 1 was carried
out in the reaction of addition of СО2 (56 atm) to cyclo-
hexene oxide (2) (Scheme 2) at various molar cata-
lyst loadings. The conversion reached 65% with an in-
creased loading of the catalyst 1 (1.2 mol%). The yields
Scheme 2
* Dedicated to Academician of the Russian Academy of Sciences
I. L. Eremenko on the occasion of his 70th anniversary.
** Department of Applied Chemistry, Indian Institute of
Technology (Indian School of Mines), Dhanbad, 826004, India.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1076—1079, June, 2020.
1066-5285/20/6906-1076 © 2020 Springer Science+Business Media LLC

Synthesis of organic carbonates
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 6, June, 2020
1077
Table 1. Addition of CO2 to cyclohexene oxide (2)а
Run
Catalyst 1/mmol
Additive/mg
Т/С
Conversion 2 (%)
1
2
3
4
5
6
7
8
0.012
0.024
0.012
0.024
0.012
0.024
0.024
0.012
0.024
0.024
0.024
0.024
0.024
—
—
110
110
110
110
110
110
110
110
110
110
110
100
180
47
65
74
92
89
91
83
85
100
94
92
95
12
TiO2
TiO2
Al2O3
Al2O3
PVA 80000
SiO2
9
SiO2
10b
11c
12
13
SiO2
SiO2
SiO2
SiO2
Reaction conditions: аsupport (0.2 mmol), additive (30 mg), 24 h, 56 atm; b 20 atm; c 10 atm.
of product 3 decrease with a decrease in catalyst amount
(0.6 mol%) (Table 1, Runs 1 and 2).
of carbon dioxide pressure from 56 to 10 atm caused
a slight decrease in the conversion (cf. Runs 9—11). We also
conducted a small series of experiments to study the effect
of temperature on the course of the reaction. So, it was
shown that the reaction proceeds only by 12% at 80 C.
Raising the temperature to 100 C provided 95% conver-
sion while the reaction reached completion at 110 C (see
Table 1, cf. Runs 9, 12, 13).
Based on our results using diammonium salt 1 and
silica gel, we can propose the reaction mechanism com-
prising the process acceleration (Scheme 3), being in
accord with those proposed for more complex systems,
and which can be extended to other supports used here.5,11
The residual hydroxy groups of silica gel interact with the
oxirane to "loosen" the bonds, which contributes to the
subsequent addition of the bromine ion coming from the
ammonium salt. The presence of a partial positive charge
on the oxygen atom promotes the activation of CO2 and
Given the potential positive effect of the support on
the conversion in this reaction,4,6,10 we decided to test
a series of compounds insoluble in organic media in order
to heterogenize the catalyst. The use of titanium dioxide
as a solid support (see Table 1, Runs 3 and 4) with constant
loading of diammonium salt 1 allowed us to increase the
conversion in both cases by about a factor of 1.5. Alumina
showed a similar effect, namely, the conversion increased
from 47 to 89% when 0.6 mol% of the ammonium salt was
used. Increased catalyst loading provides better results (see
Table 1, Runs 5 and 6). The conversion increases to 83%
when polyvinyl alcohol (Mw = 80000) is used as a support
(Run 7). Quantitative conversion was achieved using silica
gel for column chromatography as a support at 1.2 mol%
of the catalyst. A reduced loading caused a natural decrease
in the conversion (see Table 1, Runs 8 and 9). Reduction
Scheme 3

Lyubimov et al.
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Russ. Chem. Bull., Int. Ed., Vol. 69, No. 6, June, 2020
Table 2. Catalyst reuse results
Scheme 5
Cycle
Conversion (%)
1
2
3
4
5
6
100
100
100
196
187
177
Reaction conditions: support (0.4 mmol),
catalyst (0.048 mmol), SiO2 (60 mg), 24 h.
its addition. The subsequent formation of a stable five-
membered carbonate cycle leads to the release of the
bromine anion and its return to the dicationic salt.
We also conducted a series of experiments to examine
the possibility of catalyst reusing. It turned out that the
catalytic system provided quantitative conversion over
three cycles. Starting from the fourth cycle, there is a slight
decrease in the conversion (Table 2), which can be attri-
buted either to the gradual leaching of the catalyst by
a polar organic carbonate, or to the gradual thermal de-
composition of the ammonium salt.
We studied the addition of CO2 to various epoxides
4a—h (Scheme 4) under optimized reaction conditions.
The corresponding carbonates 5a—h were obtained in
quantitative yields in all cases regardless of electronic and
steric effects.
To conclude, long chain diammonium dibromide was
used as a catalyst for the reaction of CO2 addition to
epoxides. Supports are able to accelerate the passage of
the reaction. The best catalytic performance is provided
by the diammonium salt in combination with silica gel
giving the possibility of using it three times without a drop
in the conversion. It was shown that the process is very
sensitive to temperature, while the pressure of carbon
dioxide has little effect on the reaction rate of the process.
Experimental
1H, 13С, and 19F NMR spectra were registered using a Bruker
Avance 400 (400.13, 100.61, 376.5 MHz) spectrometer. Silica
gel (0.06—0.2 mm, 60 Å, Acros Organics), TiO2, Al2O3, polyvi-
nyl alcohol (Mw = 80000), 1,5-dibromopentane, triethylamine,
7-oxabicyclo[4.1.0]heptane (3), 2-(chloromethyl)oxirane (4a),
2-(phenoxymethyl)oxirane (4e), 2-phenyloxirane (4h),
2,2´-[4,4´-(propane-2,2-diyl)bis(4,1-phenylene)]bis(methylene)
bis(oxy)dioxirane (6, resin ED-22) are commercially available
compounds. 2-(Fluoromethyl)oxirane (4b), 2-(2,2,2-trifluoro-
ethyl)oxirane (4c), 2-(pentafluorophenylmethyl)oxirane (4d),
N,N-diethyl-2-oxiranemethaneamine (4f), 4-(oxirane-2-yl-
methyl)morpholine (4g) were obtained according to literature
procedures.15—19
Scheme 4
N1,N1,N1,N5,N5,N5-Hexaethylpentane-1,5-diamonium di-
bromide (1). Freshly distilled 1,5-dibromopentane (460 mg,
2 mmol) and triethylamine (1.12 mL, 8 mmol) were loaded in
a 10 mL autoclave. The mixture was kept at 110 C for 24 h,
washed with acetone (2×3 mL), and dried in vacuo. Yellowish
R = CH2Cl (a), CH2F (b), CH2CF3 (c), CH2C6F5 (d), CH2OPh (e),
CH2NEt2 (f), morpholin-4-ylmethyl (g), Ph (h)
Reagents and reaction conditions: i. 1.2 mol% 1, 30 mg SiO2, 24 h.
1
Diammonium salt 1 was also used to convert indus-
trial bis-epoxide 6 (ED-22 resin)12—14 to biscarbonate 7
(Scheme 5). Biscarbonate 7 is used in the synthesis of
macromolecular compounds with enhanced thermal and
mechanical properties, highly resistant adhesive mater-
ials, and hydrophilizing agents. Complete conversion is
achieved at a temperature of 110 °C and a pressure of
56 atm using 1.2 mol% of the catalyst in just 3 h both with
and without silica gel. The latter, possibly, is associated
with the cooperative effect of diammonium salt, simulta-
neously affecting two reaction centers of epoxide 6.
powder, yield 0.553 g (64%). H NMR (D2O): 1.15 (t, 18 H,
CH2CH3, J = 8.0 Hz); 1.28—1.39 (m, 2 H, CH2); 1.59—1.71
(m, 4 H, CH2); 3.05—3.11(m, 4 H, CH2N+); 3.17 (q, 12 H,
N+CH2CH3, J = 8.0 Hz). 13С NMR (D2O),: 6.6 (CH3), 20.8
(2 CH2), 22.7 (CH2), 52.6 (6 CH2N+), 56.1 (2 CH2N+).
Preparation of carbonates 3, 5а—h, 7 from epoxides (gen-
eral procedure). Salt 1 (5 or 10 mg, 0.012 or 0.024 mmol, respec-
tively) and the corresponding support (30 mg) were loaded in
a 10 mL autoclave, and epoxide (2 mmol) was added. Carbon
dioxide (10, 20, and 56 atm) was fed into the autoclave and
heated to 110 C in a thermostat for the required time. After
completion of the reaction, the autoclave was cooled to ~20 C,

Synthesis of organic carbonates
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 6, June, 2020
1079
CO2 was evacuated, and dichloromethane (2 mL) was added to
the residue. The slurry was filtered through a thin layer of silica
gel, and the solvent was evaporated. The reaction mass was ana-
lyzed by NMR spectroscopy. The spectral characteristics of
carbonates 3, 5a—h, 7 correspond to the data presented in the
literature.10,13,17,20—22
Reuse of the catalyst. Salt 1 (20 mg, 0.048 mmol), silica gel
(60 mg) were loaded in a 10 mL autoclave, and cyclohexene
oxide (2) (0.4 mL, 4 mmol) was added. Carbon dioxide (56 atm)
was introduced into the autoclave and the autoclave was heated
to 110 °C in a thermostat. The autoclave was cooled after the
reaction, CO2 was discharged, diethyl ether (2 mL) was added
to the residue, the mixture was filtered through a Schott filter,
the autoclave and the precipitate were further washed with di-
ethyl ether (2 mL). The catalyst from the filter was transferred
to the autoclave, cyclohexene oxide (2) was added, CO2 was fed,
and the process was repeated. After removal of diethyl ether
in vacuo, the reaction product was analyzed by NMR spectro-
scopy.
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Received January 14, 2020;
in revised form March 17, 2020;
accepted March 20, 2020