Silanediol-catalyzed carbon dioxide fixation

Article abstract of DOI:10.1002/cssc.201402783

Carbon dioxide is an abundant and renewable C₁ source. However, mild transformations with carbon dioxide at atmospheric pressure are difficult to accomplish. Silanediols have been discovered to operate as effective hydrogen-bond donor organocat

Full text of DOI:10.1002/cssc.201402783

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DOI: 10.1002/cssc.201402783
Silanediol-Catalyzed Carbon Dioxide Fixation
Andrea M. Hardman-Baldwin and Anita E. Mattson*[a]
Carbon dioxide is an abundant and renewable C1 source. How-
ever, mild transformations with carbon dioxide at atmospheric
pressure are difficult to accomplish. Silanediols have been dis-
covered to operate as effective hydrogen-bond donor organo-
catalysts for the atom-efficient conversion of epoxides to cyclic
carbonates under environmentally friendly conditions. The re-
action system is tolerant of a variety of epoxides and the de-
sired cyclic carbonates are isolated in excellent yields.
Scheme 1. Silanediols as sustainable catalysts for mild fixation of CO2.
Carbon dioxide is an ideal renewable and environmentally
friendly C1 source.[1] Unfortunately, current research lacks ap-
propriate processes to effectively utilize this reagent. As
a highly oxidized, thermodynamically and kinetically stable
molecule,[1] carbon dioxide traditionally requires harsh reaction
conditions for chemical transformations, often involving high
temperatures, high pressures, and transition-metal catalysis.[2]
Mild, metal-free reaction conditions for the sustainable utiliza-
tion of carbon dioxide remain in desirable, yet unmet,
demand.
Hydrogen-bond donor (HBD) catalysis has emerged as a re-
markable metal-free platform for the activation of organic mol-
ecules.[3] Despite its power, HBD catalysis has rarely been capi-
talized upon for controlling reactions of carbon dioxide. The
lack of appropriate reactivity of conventional catalysts may be
one reason HBDs have been slow to catch on in carbon diox-
ide fixation chemical technologies. One goal at the heart of
our own research agenda is the design and application of en-
hanced HBD catalysts with the ability to influence reactivity
patterns that are inaccessible to traditional catalysis.[4] Silane-
diols are one promising family of HBD catalysts under investi-
gation in our laboratory in a number of reactions, including
the fixation of carbon dioxide (Scheme 1). This Communication
describes our discovery of silanediols as sustainable catalysts
for ring-expansion reactions of epoxides in the presence of
carbon dioxide.
Scheme 2. Proposed mode of action for silanediol co-catalyzed CO2 activa-
tion.
ties, as well as their molecular recognition properties, led us to
hypothesize that silanediols would be ideal tools for catalyzing
reactions of carbon dioxide (Scheme 2). Specifically, we envi-
sioned a silanediol–halide ion pair (2) would affect a metal-free
CO2-insertion reaction into an epoxide, eventually giving rise
to ring-expanded carbonate products 4 via proposed inter-
mediate 3. While our experience with silanediol catalysis en-
couraged our pursuit of this new approach toward carbon di-
oxide fixation, there was no evidence to support the compati-
bility of silanediols with carbon dioxide at the onset of our
studies.[7,8]
Silanediols have excellent hydrogen-bonding capabilities.
Kondo and co-workers demonstrated the power of silanediol
hydrogen-bonds in the context of molecular recognition.[5] The
hydrogen-bonding abilities of silanediols also enable the catal-
ysis of reactions through either electrophile activation or
anion-binding processes.[6] Their demonstrated catalytic abili-
Excited to test our hypothesis, we began investigating the
100% atom economical conversion of styrene oxide to cyclic
carbonate 4a (Table 1).[9] In general, cyclic carbonates are val-
uable intermediates in polymerization and pharmaceutical
chemistry. They also function as polar aprotic solvents and can
serve as electrolytic components of lithium batteries.[10] As de-
scribed previously, the simple, albeit challenging, transforma-
tion of epoxides and carbon dioxide to cyclic carbonates often
requires harsh conditions involving high temperatures and
pressures of carbon dioxide and transition-metal catalysts for
effective conversion. Less harsh conditions have been recently
reported in a limited number of metal-free systems,[11] but
a general organocatalytic system for the mild reaction of
carbon dioxide and epoxides remains a challenge. We envi-
[a] A. M. Hardman-Baldwin, Prof. Dr. A. E. Mattson
Department of Chemistry and Biochemistry
The Ohio State University
100 W. 18thAve., Columbus, Ohio 43210 (USA)
E-mail: mattson@chemistry.ohio-state.edu
Homepage: http://mattson.group.chemistry.ohio-state.edu/
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cssc.201402783.
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Table 1. Optimization of reaction conditions.[a]
Table 2. Hydrogen-bond donor catalyst screen.[a]
TBAX[b]
Solvent
T
[h]
T
[8C]
Yield[c]
[%]
Catalyst
Yield[b] Catalyst
[%]
Yield[b]
[%]
Entry
Loading of 5
[mol%]
5
93
9
58[c]
38[c]
87
1
2
3
4
5
6
7
8
9
10
10
10
10
5
10
10
10
10
TBAB
TBAB
TBAB
TBAI
TBAI
TBAI
TBAI
TBAI
TBAI
PhMe
neat
neat
neat
neat
PhMe
EtOAc
MEK
24
14
18
18
24
18
18
18
18
60
60
23
23
23
40
40
40
40
89
95
49
93
83
91
70
85
88
6
7
1[c]
10
11
acetone
[a] All reactions performed using a balloon of CO2 at 1 bar. [b] 1:1 mol%
loading as catalyst 5. [c] Isolated yield.
60
34
sioned that our silanediols would be able to affect this trans-
formation under mild reactions conditions while simultaneous-
ly accommodating a variety of reactant epoxides.
8
12
82
SiO2 (10 wt%)
We were pleased early on to find that our dinaphthyl silane-
diol 5 was indeed compatible with carbon dioxide. Styrene
oxide afforded 89% yield of 4a with 10 mol% of catalyst 5
under an atmosphere of carbon dioxide in 2m toluene using
tetrabutylammonium bromide (TBAB) as a co-catalyst (entry 1,
Table 1). Determined to find more environmentally friendly
conditions, further optimization of the reaction conditions was
investigated. We first observed that solvent was often unneces-
sary for the reaction: neat conditions at 608C increased the
yield to 95% (entry 2). After our initial disappointment that
temperatures below 608C did not provide high yields (entry 3),
we discovered that switching to tetrabutylammonium iodide
(TBAI) as co-catalyst afforded excellent yields of 4a at 238C
(entry 4). Lowering the loading of silanediol catalyst 5 from 10
to 5 mol% resulted in a small loss in yield (entry 5). A variety
of green solvents (5m) afforded excellent conversions albeit at
slightly increased temperature (entries 6–9).[12]
[a] All reactions performed using a balloon of CO2 at 1 bar. [b] Isolated
yield. [c] 1H NMR yield using mesitylene as an internal standard.
A variety of epoxide substrates were tested under our opti-
mal reaction conditions (Table 3). A wide range of aromatic ep-
oxides was well tolerated in the system providing excellent
yields of cyclic carbonates 4a–4d (73–97%). The epoxide de-
rived from allylbenzene operated well in the reaction system,
giving rise to 4e in 96% yield. 2-(Benzyloxy)methyloxirane
gave rise to an excellent yield of product 4 f. Alkyl epoxides
also underwent ring expansion within this reaction system and
gave rise to good yields of products 4g and 4h. It is worth-
while to mention that the best reactivity of volatile alkyl epox-
ides, such as propylene oxide, is achieved in the presence of
solvent. At this time, the reaction system is limited to mono-
substituted epoxides as poor conversion was observed with
several disubstituted epoxides tested; efforts are underway in
our laboratory to enable reactions with these substrates.
A family of catalysts was then tested under our optimized
reactions conditions found in entry 4 of Table 1. Dimethoxysi-
lane 6, a catalyst that cannot donate hydrogen- bonds, provid-
ed no conversion to the desired carbonate product and con-
firmed the necessity of the hydrogen-bonding functionality
(Table 2). Triphenylsilanol 7 provided only 60% yield of the car-
bonate product suggesting that the dual hydrogen-bonding
capabilities of 5 is a key factor in the success of the reaction.
Phenols have been shown to affect the conversion of epoxides
to cyclic carbonates as HBD catalysts,[11d,g,13] but were not as ef-
fective under our reaction conditions (catalysts 11 and 12). In-
terestingly, traditional 1,3-bis(3,5-bis(trifluoromethyl)phenyl)ur-
ea 9 and thiourea 10 HBD catalysts did not operate well under
these reaction conditions. This suggests that silanediol cata-
lysts are uniquely suited for the activation of epoxides. Control
Taking into account previous mechanistic investigations on
g,13,14]
related systems[7,11c,
and our own experimental observa-
tions, a proposed reaction pathway is depicted in Scheme 3.
Initial activation of the epoxide by dual hydrogen-bonding
with the silanediol yields I. The epoxide then undergoes ring-
opening upon nucleophilic attack of the iodide co-catalyst[15]
to yield hydrogen-bond-stabilized alkoxide II.[16] The addition
of II to carbon dioxide generates silanediol-stabilized inter-
mediate III. The completion of the catalytic cycle occurs upon
intramolecular ring closure of III to generate the cyclic carbon-
ate 4, iodide, and silanediol 5.
1
experiments resulted in a 1% H NMR yield in the absence of
To gain insight into the proposed reaction pathway, optically
pure (R)-styrene oxide was tested under our optimized condi-
tions to determine if chirality would transfer from the epoxide.
a HBD catalyst; without the presence of the co-catalyst, no
conversion to the desired product was observed.
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Table 3. Substrate scope.[a]
Carbonate product
Yield[b]
[%]
Carbonate product
Yield[b]
[%]
4a
93
4b
97
4c
88
4d[c]
73
4e
4g
96
82
4 f
96
74
4h[c]
[a] All reactions performed using a balloon of CO2 at 1 bar. [b] Isolated
yield. [c] Experiment reacted in 5m toluene for 18 h at 408C.
Figure 1. Binding titrations with silanediol 5: (a) Tetrabutylammonium
iodide-silanediol binding and (b) styrene oxide-silanediol binding.
the silanediol caused downfield shifting of the OÀH peak (Fig-
ure 1b).12]
In conclusion, silanediols operate as a sustainable class of
catalysts for the reaction of carbon dioxide with epoxides
under mild reaction conditions. A variety of epoxides are trans-
formed into their corresponding cyclic carbonates with excel-
lent yields under environmentally friendly conditions using
only an atmosphere of carbon dioxide. With this mild method-
ology, chirality of aromatic epoxides is transferred to the corre-
sponding cyclic carbonate product with minimal loss in enan-
tioenrichment. The demonstration of the compatibility of sila-
nediol catalysis and carbon dioxide provides a new platform
for the development of innovative reactivity patterns previous-
ly unattainable with traditional hydrogen-bond donor cata-
lysts.
Scheme 3. Proposed reaction pathway for cyclic carbonate formation.
We isolated the carbonate product in 95% enantiomeric
excess (ee), providing evidence for the ring opening of the ep-
oxide by the iodide ion.[13b-d] This environmentally friendly
method provides access to enantioenriched aromatic carbon-
ate products with minimal racemization from the initial epox-
ide.[12]
1
Qualitative H NMR titration studies demonstrated silanediol
recognition of both the epoxide and iodide through proposed
hydrogen-bonding interactions (Figure 1). Upon addition of
tetrabutylammonium iodide to the silanediol catalyst, down-
field shifting of the silanediol OÀH chemical signal was ob-
served (Figure 1a). Similarly, the addition of styrene oxide to
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c) D. Nickerson, V. V. Angeles, A. E. Mattson, Org. Lett. 2013, 15, 5000;
d) T. J. Auvil, S. S. So, A. E. Mattson, Angew. Chem. Int. Ed. 2013, 52,
11317; Angew. Chem. 2013, 125, 11527; e) D. Nickerson, V. V. Angeles,
T. J. Auvil, S. S. So, A. E. Mattson, Chem. Commun. 2013, 49, 4289;
f) A. M. Hardman, S. S. So, A. E. Mattson, Org. Biomol. Chem. 2013, 11,
5793; g) S. S. So, A. E. Mattson, J. Am. Chem. Soc. 2012, 134, 8798.
[5] S. Kondo, T. Harada, R. Tanaka, M. Unno, Org. Lett. 2006, 8, 4621.
[6] a) A. G. Schafer, J. M. Wieting, T. J. Fisher, A. E. Mattson, Angew. Chem.
Int. Ed. 2013, 52, 11321; Angew. Chem. 2013, 125, 11531; b) N. T. Tran,
S. O. Wilson, A. K. Franz, Org. Lett. 2012, 14, 186; c) ; N. T. Tran, T. Min,
A. K. Franz, Chem. Eur. J. 2011, 17, 9897; d) A. G. Schafer, J. M. Wieting,
A. E. Mattson, Org. Lett. 2011, 13, 5228.
[7] During preparation of this manuscript an example of a silicon-based
polyimidazolium salt was published featuring silanol activation of epox-
ides: J. Wang, J. Leong, Y. Zhang, Green Chem. 2014, 16, 4515.
[8] Silica gel has been used as a co-catalyst in carbonate formation reac-
tions. For related examples: a) B. Song, L. Guo, R. Zhang, X. Zhao, H.
Gan, C. Chen, J. Chen, W. Zhu, Z. Hou, J. CO2 Util. 2014, 6, 62; b) T. Taka-
hashi, T. Watahiki, S. Kitazume, H. Yasuda, T. Sakakura, Chem. Commun.
2006, 1664; c) J.-Q. Wang, D.-L. Kong, J.-Y. Chen, F. Cai, L.-N. He, J. Mol.
Catal. A 2006, 249, 143.
[9] For reviews on cyclic carbonate formation see: a) M. Tamura, M. Honda,
Y. Nakagawa, K. Tomishige, J. Chem. Technol. Biotechnol. 2014, 89, 19;
b) C. J. Whiteoak, A. W. Kleij, Synlett 2013, 24, 1748; c) M. North, R. Pas-
quale, C. Young, Green Chem. 2010, 12, 1514; d) A. Decortes, A. M. Cas-
tilla, A. W. Kleij, Angew. Chem. Int. Ed. 2010, 49, 9822; Angew. Chem.
2010, 122, 10016; e) M. Yoshida, M. Ihara, Chem. Eur. J. 2004, 10, 2886.
[10] a) B. Schꢂffner, F. Schꢂffner, S. Verevkin, A. Bçrner, Chem. Rev. 2010, 110,
4554; b) T. Sakakura, K. Kohno, Chem. Commun. 2009, 1312; c) J. Clem-
ents, Ind. Eng. Chem. Res. 2003, 42, 663; d) J. P. Parrish, R. N. Salvatore,
K. W. Jung, Tetrahedron 2000, 56, 8207; e) A. Shaikh, S. Sivaram, Chem.
Rev. 1996, 96, 951.
Experimental Section
Procedure for preparation of 4a: A dry, screw-capped reaction vial
containing a magnetic stir bar was charged with silanediol 5
(27.6 mg, 0.087 mmol, 0.1 equiv.), tetrabutylammonium iodide
(32.3 mg, 0.087 mmol, 0.1 equiv.) and styrene oxide 1a (100 mL,
0.874 mmol, 1 equiv.). The vial was fitted with a cap and septa and
degassed with carbon dioxide. The vial was put under a positive
pressure with a balloon of carbon dioxide and allowed to stir at
room temperature for 18 h. After the reaction time, mesitylene
(40.5 mL, 0.291 mmol, 0.33 equiv.) and CDCl3 were added to the vial
and stirred for 1 min. A 1H NMR sample was taken to determine
the yield with mesitylene as the internal standard. The NMR
sample and the reaction vial were combined, and the carbonate
product isolated via flash column chromatography using silica gel
(5:95 diethyl ether/hexanes to 50:50 diethyl ether/hexanes). The
isolated yield of carbonate products correlated with the yield de-
1
termined by H NMR spectroscopy using the internal standard. All
isolated carbonate products matched reported characterization
data.[12]
4-phenyl-1,3-dioxolane-2-one (4a): Isolated as
a white solid.
1H NMR yield: 95%. Isolated yield: 93%. Rf =0.20 (40:60 diethyl
ether/hexanes). 1H NMR (400 MHz, CDCl3): d=7.47–7.42 (m, 3H);
7.38–7.35 (m, 2H); 5.67 (apparent t, J=8 Hz, 1H); 4.79 (apparent t,
J=8.4 Hz, 1H); 4.36–4.32 ppm (m, 1H); 13C NMR (100 MHz, CDCl3):
d=154.8, 135.8, 129.7, 129.2, 125.8, 77.9, 71.1 ppm. All other spec-
troscopic data matched that previously reported. See the Support-
ing Information for characterization data of other compounds re-
ported.
[11] a) M. E. Wilhelm, M. H. Anthofer, M. Cokoja, I. I. E. Markovits, W. A. Herr-
mann, F. E. Kꢁhn, ChemSusChem 2014, 7, 1357; b) B. Chatelet, L. Joucla,
J.-P. Dutasta, A. Martinez, V. Dufaud, Chem. Eur. J. 2014, 20, 8571; c) J.
Sun, W. Cheng, Z. Yang, J. Wang, T. Xu, J. Xin, S. Zhang, Green Chem.
2014, 16, 3071; d) C. J. Whiteoak, A. H. Henseler, C. Ayats, A. W. Kleij,
M. A. Pericꢃs, Green Chem. 2014, 16, 1552; e) J. Kozak, J. Wu, S. Xiao, S.
Fritz, T. A. Hatton, T. Jamison, J. Am. Chem. Soc. 2013, 135, 18497; f) B.
Chatelet, L. Joucla, J. P. Dutsta, A. Martinez, K. Szeto, V. Dufaud, J. Am.
Chem. Soc. 2013, 135, 5348; g) C. J. Whiteoak, A. Nova, F. Maseras, A. W.
Kleij, ChemSusChem 2012, 5, 2032; h) B. Barkakaty, K. Morino, A. Sudo, T.
Endo, Green Chem. 2010, 12, 42.
Acknowledgements
Support for this work has been provided by the OSU Department
of Chemistry and Biochemistry and the Donors of the American
Chemical Society Petroleum Research Foundation (Award No.
52183-DNI1).
[12] See the Supporting Information for additional experimental details in-
volving reaction conditions, silanediol catalyst, and product isolation.
[13] a) J.-Q. Wang, J. Sun, W.-G. Cheng, K. Dong, X.-P. Zhang, S.-J. Zhang,
Phys. Chem. Chem. Phys. 2012, 14, 11021; b) Y.-M. Shen, W.-L. Duan, M.
Shi, Eur. J. Org. Chem. 2004, 3080; c) Y. Shen, W. Duan, M. Shi, Adv.
Synth. Catal. 2003, 345, 337; d) J. Huang, M. Shi, J. Org. Chem. 2003, 68,
6705.
Keywords: carbon dioxide · cyclic carbonate · hydrogen-bond
donors · metal-free catalysis · silanediol
[1] For recent reviews on carbon dioxide utilization see: a) Y. Oh, X. Hu,
Chem. Soc. Rev. 2013, 42, 2253; b) N. Kielland, C. J. Whiteoak, A. W. Kleij,
Adv. Synth. Catal. 2013, 355, 2115; c) Z.-Z. Yang, L.-N. He, J. Gao, A.-H.
Liu, B. Yu, Energy Environ. Sci. 2012, 5, 6602; d) A. H. Liu, Y. N. Li, L. N.
He, Pure Appl. Chem. 2012, 84, 581; e) M. Mikkelsen, M. Jørgensen, F. C.
Krebs, Energy Environ. Sci. 2010, 3, 43; f) S. N. Riduan, Y. Zhang, Dalton
Trans. 2010, 39, 3347; g) M. Aresta, Carbon Dioxide as a Chemical Feed-
stock, Wiley-VCH, Weinheim, 2010; h) M. Aresta, A. Dibenedetto, Dalton
Trans. 2007, 2975; i) T. Sakakura, J.-C. Choi, H. Yasuda, Chem. Rev. 2007,
107, 2365.
[2] For recent reviews of metal catalysis with carbon dioxide see: a) Y. Tsuji,
T. Fujihara, Chem. Commun. 2012, 48, 9956; b) D. J. Darensbourg, S. J.
Wilson, Green Chem. 2012, 14, 2665; c) M. Cokoja, C. Bruckmeier, B.
Rieger, W. A. Herrmann, F. E. Kꢁhn, Angew. Chem. Int. Ed. 2011, 50, 8510;
Angew. Chem. 2011, 123, 8662; d) M. Kember, A. Buchard, C. Williams,
Chem. Commun. 2011, 47, 141; e) K. Huang, C. Sun, Z. Shi, Chem. Soc.
Rev. 2011, 40, 2435; f) C. Federsel, R. Jackstell, M. Beller, Angew. Chem.
Int. Ed. 2010, 49, 6254; Angew. Chem. 2010, 122, 6392.
[14] a) T. Werner, N. Tenhumberg, J. CO2 Util. 2014, 7, 39;b) A. Zhu, T. Jiang,
B. Han, J, Zhang, Y. Xie, X. Ma, Green Chem. 2007, 9, 169.
[15] Scheme 3 depicts opening the epoxide from the terminal carbon; we
acknowledge that ring opening could occur at either position for aro-
matic epoxides. For insights into regioselectivity of metal catalysts see:
a) R. Luo, Z. Zhou, W. Zhang, Z. Liang, J. Jiang, J. Ji, Green Chem. 2014,
16, 4179; b) N. D. Harrold, Y. Li, M. H. Chisholm, Macromolecules 2013,
46, 692; c) F. Castro-Gꢄmez, G. Salassa, A. W. Kleij, C. Bo, Chem. Eur. J.
2013, 19, 6289; d) P. P. Pescarmona, M. Taherimehr, Catal. Sci. Technol.
2012, 2, 2169; e) G.-P. Wu, S.-H. Wei, W.-M. Ren, X.-B. Lu, B. Li, Y.-P. Zu,
D. J. Darensbourg, Energy Environ. Sci. 2011, 4, 5084; f) G.-P. Wu, S.-H.
Wei, X.-B. Lu, W.-M. Ren, D. J. Darensbourg, Macromolecules 2010, 43,
9202.
[16] For an example of dual hydrogen-bond donor stabilization of alkoxide
intermediates see: M. Kotke, P. R. Schreiner, Tetrahedron 2006, 62, 434.
[3] a) A. Berkessel, H. Groger, Asymmetric Organocatalysis, 1st ed., Wiley-
VCH, 2005; b) P. Pihko, Hydrogen Bonding in Organic Synthesis Wiley-
VCH, Weinheim, 2000.
Received: July 31, 2014
[4] a) T. J. Fisher, A. E. Mattson, Org. Lett. 2014, DOI: 10.1021/ol502494h;
b) T. J. Auvil, A. S. Schafer, A. E. Mattson, Eur. J. Org. Chem. 2014, 2633;
Published online on October 19, 2014
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