Efficient Catalysts In situ Generated from Zinc, Amide and Benzyl Bromide for Epoxide/CO2 Coupling Reaction at Atmospheric Pressure

Article abstract of DOI:10.1002/ejoc.201801653

Herein, in situ generated efficient catalysts were designed for fixation of CO₂ to cyclic carbonates under mild conditions. Zinc bromide and N,N-dibenzyl-N,N-dimethylammonium bromide, being proved as active catalyst species, were in situ generated from cheap Zn powder, dimethyl formamide and benzyl bromide, and catalyzed the cycloaddition reaction of CO₂ and various terminal epoxides in moderate to excellent yields at 80 °C and atmospheric pressure of CO₂. The protocol circumvents the preparation of active catalysts, simultaneously possesses good catalytic activity under mild conditions.

Full text of DOI:10.1002/ejoc.201801653

A Journal of
Accepted Article
Title: Efficient Catalysts In Situ Generated from Zinc, Amide and
Benzyl Bromide for Epoxide/CO2 Coupling Reaction at
Atmospheric Pressure
Authors: Shuai Zhang, Feng Han, Shaorui Yan, Mingyue He, Chengxia
Miao, and Liang-Nian He
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201801653
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10.1002/ejoc.201801653
European Journal of Organic Chemistry
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Efficient Catalysts In Situ Generated from Zinc, Amide and Benzyl
Bromide for Epoxide/CO2 Coupling Reaction at Atmospheric
Pressure
Shuai Zhang,*[a,b] Feng Han,[b] Shaorui Yan,[b] Mingyue He, [b] Chengxia Miao,[b] and Liang-Nian He*[a]
Dedication ((optional))
Abstract: Herein, in situ generated efficient catalysts were designed
for fixation of CO2 to cyclic carbonates under mild conditions. Zinc
bromide and N,N-dibenzyl-N,N-dimethylammonium bromide, being
proved as active catalyst species, were in situ generated from cheap
Zn powder, dimethyl formamide and benzyl bromide, and catalyzed
the cycloaddition reaction of CO2 and various terminal epoxides in
moderate to excellent yields at 80 oC and atmospheric pressure of
CO2. The protocol circumvents the preparation of active catalysts,
simultaneously possesses good catalytic activity under mild
conditions.
as a nucleophile usually shows excellent catalytic efficiency. The
halide anion can be incorporated in the metal complex or added
into catalytic system. Kleij group developed aluminum-
aminotriphenolate complexes with tetrabutylammonium iodine
as co-catalyst, which showed excellent catalytic activity.[4] Ema
and coworkers synthesized bifunctional MgII porphyrin catalysts
bearing eight tetraalkylammonium bromide groups with alkyl
chain, which presented high catalytic activity (turnover frequency,
19,000 h-1).[5] Bifunctional polymers by combining imidazolium-
based ionic liquids with zinc(II) porphyrin were designed by Ji
group, and exhibited good catalytic performance and excellent
recyclability. [6]
Despite of great achievements, examples of active metal
catalyst in situ generated from commonly available reagents with
simple synthetic process are limited. Development of active
catalysts through simple strategies from cheap, easily-obtained,
low-toxic materials under mild conditions is still desirable. The
integration of catalyst formation and subsequent catalysis is
dependent on the rational design of efficient catalyst and its
compatibility with the reaction system. Hirose group employed
iminium salts in situ generated from benzyl bromide (BnBr) and
N,N-dimethylformamide (DMF) for the coupling of CO2 and
epoxide at 120 oC, 1 bar CO2.[7] Our group described in situ
Introduction
Carbon dioxide, as a plentiful, low-cost, nontoxic, sustainable C1
synthon, has gained increasing attention.[1] The chemical CO2
fixation to value-added commodity chemicals, fuels and
materials, nowadays, has been becoming one of research
hotspots in both academy and industry.[1] CO2 has been utilized
in both the synthesis of organic carbonate, various important
heterocycles, and the reduction to methanol, formic acid and so
on. In the pursuit of the CO2-based products, the coupling
reaction of CO2 and epoxides to afford cyclic carbonates
(Scheme 1),[2] one of the few commercial routes with CO2 as a
raw material, is of great importance and has been a hot topic in
catalysis, being ascribed to the unique properties of cyclic
carbonate. Organic carbonates have been widely used as
excellent high-boiling polar aprotic solvents, important
intermediates in the production of pharmaceuticals and
electrolytic elements of lithium secondary batteries.[2] In the past
decades, numerous homogeneous and heterogeneous catalysts
have been well developed by many research groups for efficient
synthesis of cyclic carbonates, including metal oxides,
(transition) metal complexes,[3a-e] alkali metal salts,[3f-g] ionic
liquids,[3h] organocatalysts[3i] and so on. Furthermore, the
application of a metal complex in conjunction with a halide anion
generated
ZnCl2(TBD)2
complex
(TBD:
1,5,7-
triazabicyclo[4.4.0]dec-5-ene) acted as a robust catalyst for the
carboxylative cyclization of propargylic amines with CO2 without
pre-preparation and further isolation.[8]
Zinc, presenting high natural abundance and low
environmental impact, has found wide application in the field of
CO2 utilization for the past decades.[9] For the cycloaddition
reaction, a series of zinc salts/ionic liquid binary catalysts, such
as ZnCl2/[BMIm]Br,[7a-b] ZnBr2/n-Bu4NI,[7c] Zn(OPO)2/n-Bu4NI,[7d]
Zn4(OCOCF3)6O/n-Bu4NI,[7e] have been developed, and their
high catalytic efficiency presumably is ascribed to that the
effective activation of epoxide by the Lewis acidic Zn2+ cation
facilitates the ring-opening at the less substituted C-O bond
upon nucleophilic attack by halide anion.[10]
Herein, we envisioned that active binary catalysts could be in
situ generated from Zn powder, DMF and BnBr. Iminium salts
generated from BnBr and DMF[7] would be reduced[11] and
hydrolysed in presence of zinc powder and trace water, to
provide ZnBr2 and N,N-dibenzyl-N,N-dimethylammonium
bromide ([DBDMA]Br). ZnBr2/[DBDMA]Br binary catalysts
containing a Lewis acidic center and a Brønsted basic center,
were in situ generated from Zn powder, DMF and BnBr, and
served as active catalysts in one pot for the cycloaddition
reaction of CO2 and epoxide at 80 oC and atmospheric pressure
of CO2 (Scheme 1).
[a]
L.-N. He
State Key Laboratory and Institute of Elemento-Organic Chemistry,
College of Chemistry
Nankai University
Tianjin 300071, China
E-mail: heln@nankai.edu.cn
S. Zhang, F. Han, S. Yan, M. He, C. Miao
College of Chemistry and Material Science
Institution Shandong Agricultural University
Taian 271018, Shandong Province, China
E-mail: hyzs@sdau.edu.cn
[b]
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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10.1002/ejoc.201801653
European Journal of Organic Chemistry
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Table 1. Catalytic cycloaddition of CO2 with 1a by Zn
powder/BnBr/amide.[a]
Entry
1
Metal
---
Amide
DMF
---
Conv. (%)
Yield (%)
4
4
2
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Mn
Mg
Fe
Al
<1
<1
>99
75
44
>99
78
94
93
85
>99
34
23
40
93
<1
<1
0
3[b]
4
DMF
DMF
DMAc
DEAc
DMSO
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
0
Scheme 1. In situ generated active catalysts for the cycloaddition reaction of
epoxide and CO2.
97
74
43
39
74
93
92
22
95
34
18
34
54
0
5
6[c]
7
Results and Discussion
Initially, styrene oxide (1a) was chosen as model substrate for
the cycloaddition reaction at 80 oC and atmospheric CO2
pressure, and Zn powder, DMF and BnBr were selected as raw
materials to generate the proposed binary catalysts. As
summarized in Table 1, in the absence of Zn, DMF or BnBr
respectively, almost no product was observed with no obvious
conversion of 1a (entries 1-3), indicating no active catalysts
were generated. Inspiringly, the combination of Zn
powder/DMF/BnBr resulted in excellent yield (97%, entry 4),
suggesting active catalysts were generated and catalyzed the
cycloaddition reaction. Subsequently, the effects of Zn, DMF and
BnBr were investigated respectively. The replacement of DMF
by DMAc and DEAc provided the corresponding carbonate 2a
with relatively lower yields albeit with good selectivity (entries 5-
6). However, the application of DMSO resulted in significantly
reduced selectivity (39%, entry 7). Interestingly, the employment
of anhydrous DMF led to reduced yield (74%, entry 8), and a
retention of high yields was observed by adding 5, 10 mol%
distilled water into the reaction system (entries 9, 10), indicating
that moisture probably was involved in the generation of active
catalysts. Taking into consideration that polar DMF as solvent
probably enhanced the reactivity, CHCl3 instead of DMF was
used employed, which resulted in lower yield (22%, entry 11). It
indicates that DMF promotes the cycloaddition mainly by
facilitating the generation of active catalysts. The employment of
newly activated Zn powder gave similar yield (95%, entry 12)
with that of non-activated powder. Therefore, non-activated Zn
powder was used in the following experiments. On the other
hand, the alternative of metal (such as Mn, Mg, Fe, Al) or BnBr
in this cycloaddition reaction gave an adverse effect (entries 13-
18). The employment of Zn powder delivered excellent yield
(97%, entry 4), while Mn, Mg, Fe resulted in poor yields (entries
13-15), and Al powder gave poor selectivity (entry 16). These
results are probably attributed to that no corresponding active
intermediates were generated according to the proposed
pathway, proving the subtlety of this catalytic system. When
BnBr was replaced by relatively less active benzyl chloride and
1-(chloromethyl)-4-nitrobenzene (entries 17-18), all the reactants
were recovered, indicating no generation of any active catalysts.
8[d]
9[e]
10[f]
11[g]
12[g]
13
14
15
16
17[i]
18[j]
Zn
Zn
0
[a] Reaction conditions: 1a (5 mmol, 601.5 mg), metal powder (0.25 mmol,
5 mol%), amide (500 mg), BnBr (42.8 mg, 0.25 mmol, 5 mol%), CO2
balloon, 80 oC, 12 h; the conversion and yield were determined by 1H NMR
using 1,3,5-trimethoxybenzene as the internal standard. [b] Without BnBr.
[c] DEAc = diethylacetamide. [d] Anhydrous DMF. [e] Distilled water 4.5 g,
5 mol%. [f] Distilled water 9.0 g, 10 mol%. [g] DMF (0.25 mmol, 5 mol%),
CHCl3 (500 mg) as solvent. [h] Activatted Zn powder. [i] Benzyl chloride
(31.6 mg, 5 mol%) instead of BnBr. [j] 1-(Chloromethyl)-4-nitrobenzene
(42.9 mg, 5 mol%) instead of BnBr.
In situ FTIR (Fourier Transform Infrared Spectroscopy)
under 1 bar of CO2 pressure was also performed to gain insight
into the cycloaddition reaction. Figure 1 explicitly shows the
peak change with reaction time. Initially, almost no epoxide was
consumed in 1.5 h, and slight decrease of peaks at 1094 and
1388 cm-1 belonging to the absorption of DMF was observed
during the 1.5 h, which probably was ascribed to the process of
in situ generation of active catalysts. Subsequently, absorption
peak of the carbonyl group at 1806 cm-1 increased gradually,
indicating the beginning of the cycloaddition reaction. The
weakening of the signal at 875 cm-1 (benzene skeleton vibration)
of 1a was accompanied with the increasing peaks at 1164 and
1068 cm-1 (C-O stretching vibration) of 2a, suggesting the
smooth running of the cycloaddition process.
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10.1002/ejoc.201801653
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To provide further evidences to support the proposed in situ
generation of active catalysts, control reactions involving Zn
powder/DMF/BnBr were performed to obtain the proposed ZnBr2
and tetraalkylammonium bromide. Expectedly, as shown in
Scheme 2a, ZnBr2, [DBDMA]Br and dibenzyl ether were
generated and isolated by column chromatography. Peaks at 2θ
= 13.64o, 21.25o, 25.98o, 27.50o, 28.24o, 31.31o, 35.02o, 46.04o
in the XRD (X-ray powder diffraction) spectrum (Figure S1) are
ascribed to ZnBr2 (JCPDS #No. 36-0756). [DBDMA]Br and
dibenzyl ether were characterized by NMR (nuclear magnetic
resonance) spectra. As shown in Scheme 2a, excessive Zn
powder was used, which was agreement with that residue Zn
powder was found after the experiments. As shown in Scheme
2a, to convert one mol BnBr completely, 3/8 mol Zn powder
would be consumed. If using this stoichiometry for the
conversion of 1a (Zn 1.87 mol%, BnBr 5 mol%), 81% yield of 2a
was obtained with 83% conversion (Scheme 2b). Therefore, to
promote the generation of active catalysts, 5 mol% Zn powder
was used in the cycloaddition reaction. According to Scheme 2a,
the amount of ZnBr2 and [DBDMA]Br generated in the
cycloaddition reaction were calculated to be approximately 1.25
mol%, which whereafter was used in Scheme 2b. Although pure
ZnBr2 or [DBDMA]Br (1.25 mol%) as sole catalyst could also
catalyze the cycloaddition reaction, the relative lower yield (60%,
82%, respectively) suggests that ZnBr2 or [DBDMA]Br alone is
not the real catalyst. The combination of ZnBr2 and [DBDMA]Br
gave high yield (95%), which was consistent with the results in
Table 1. Therefore, based on these results above,
ZnBr2/[DBDMA]Br was in situ generated and served as the real,
active catalysts for the coupling reaction of 1a and CO2.
Figure 1. In situ FTIR spectra for the coupling reaction. 1a (2.40 g, 20 mmol),
Zn powder (65.4 mg, 5 mol%), DMF (1.50 g), BnBr (171.0 mg, 5 mol%), 80 oC,
CO2 (balloon).
To survey the applicability of this in situ generated active
catalysts, various functionalized terminal epoxides were tested
o
at atmospheric CO2 pressure, 80 C. As listed in Scheme 3, a
series of epoxides were smoothly converted to the
corresponding cyclic carbonates (2a–h) in excellent yields (up to
99%). Interestingly, probably being ascribed to the steric effect,
isobutylene carbonate 2i exhibited relatively lower yield even
under harsh conditions.
Scheme 3. Substrate scope. Unless otherwise stated, the reactions were
carried out with 5.0 mmol substrate in the presence of DMF (500 mg), BnBr
(42.8 mg, 0.25 mmol), Zn powder (16.3 mg, 0.25 mmol) at 80 °C, CO2
(balloon), 12 h; yields were determined by 1H NMR with 1,3,5-
trimethoxybenzene as the internal standard; isolated yields were listed in
brackets. [a] 25 mL stainless-steel autoclave equipped with an inner glass
tube, 0.5 MPa CO2. [b] 120 oC.
Scheme 2. Control experiments. (a) Zn powder (130.6 mg, 2 mmol), BnBr
(342.1 mg, 2 mmol), DMF (500 mg), 80 oC, 12 h. (b) 1a (601.5 mg, 5 mmol),
DMF 500 mg, 80 oC, 12 h, CO2 (balloon). [a] Isolated yield. [b] Determined by
GC using diphenyl as an internal standard. [c] 83% conversion. [d] 96%
conversion of 1a.
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10.1002/ejoc.201801653
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Experimental Section
General
Propylene oxide were purchased from Alfa Aesar, other epoxides, BnBr,
benzyl chloride, 1-(chloromethyl)-4-nitrobenzene and anhydrous DMF
were of analytical grade and obtained from Shanghai Aladdin Bio-Chem
Technology Co., LTD. DMF, DMAc, DEAc, DMSO and metal powders
were purchased from Tianjin Guangfu Fine Chemical Research Institute.
All reagents were used without further purification. Carbon dioxide with a
purity of 99.9% was commercially available. Activated Zn powder was
obtained according to reference 14. The products were characterized by
NMR spectra. 1H NMR spectra were recorded on 400 MHz
spectrometers using CDCl3 as solvents referenced to CDCl3 (7.26 ppm).
13C NMR spectra were recorded at 100.6 MHz in CDCl3 (77.16 ppm).
Gas chromatograph (Shimadzu 2014 chromatographer) is equipped with
a RTX-50 capillary column (30 m × 0.25 mm) using a flame ionization
detector (FID). In situ FTIR spectra were collected on a Mettler Toledo
React IR ic10, Diamond ATR probe, by using an ic IR analysis system.
The probe was placed in the middle of the mixture, which was constantly
stirred magnetically, and the spectra were collected in situ during the
cycloaddition reaction. ESI-MS was recorded on an LCQ-Advantage
instrument from Thermo-Finnigan.
Scheme 4. Proposed mechanism of the generation of catalysts and the
cycloaddition reaction.
General procedure for the cycloaddition reaction of epoxide with
CO2
The cycloaddition reaction of epoxide and CO2 was conducted in a 10
mL Schlenk flask. In a typical reaction, the flask was charged with Zn
powder (16.3 mg, 0.25 mmol), BnBr (42.8 mg, 0.25 mmol), DMF (500
mg), and epoxides (0.50 mmol) successively at room temperature. The
flask was capped with a stopper and sealed. Then, the reaction mixture
was stirred at 80 °C for 12 h under an atmosphere of CO2 (1.5 L-balloon).
After the reaction was completed, the mixture was cooled to room
temperature and 1,3,5-trimethoxybenzene as internal standard was
added. The conversion of epoxides and yield of cyclic carbonates were
determined by 1H NMR in CDCl3. Then, the residue was further purified
by column chromatography (silica gel as stationary phase) with ethyl
acetate-petroleum ether as the eluent to afford product. All cyclic
carbonates 2a-i have been reported previously and the characterization
data are all in good agreement with literature value.[10d]
Accordingly, based on these results and previous reports,
two successive processes were proposed in this reaction,
including the generation of active catalysts and the cycloaddition
(Scheme 4). Initially, DMF interacted with BnBr to generate
iminium salt A.[7] The resulting iminium salts A was then reduced
through umpolung conversion reaction by way of two-electron
transfer in the presence of Zn powder to generate complex B.[12]
The complex B was highly reactive, and could be rapidly
hydrolysed to generate benzyloxy zinc bromide, formaldehyde
and dimethylamine, and immediately convert to ZnBr2 and
[DBDMA]Br in the presence of BnBr.[11,13] Subsequently, the
generated binary ZnBr2/[DBDMA]Br catalyzed the coupling
reaction, which initiated with the interaction of oxygen atom in
epoxide with Lewis acidic Zn2+ center in ZnBr2 (C), facilitating the
ring-opening by nucleophilic attack of Br anion of [DBDMA]Br to
generate an alcoholate D. Then CO2 was introduced to form the
intermediate E followed by an intramolecular cyclization to
obtain the targeted compounds with the regeneration of
ZnBr2/[DBDMA]Br.
4-Phenyl-1,3-dioxolan-2-one (2a): 1H NMR (400 MHz, CDCl3) δ 7.49-
7.30 (m, 5H), 5.68 (t, J = 8.0 Hz, 1H), 4.78 (t, J = 8.4 Hz, 1H), 4.33 (t, J =
8.2 Hz, 1H); 13C NMR (100.6 MHz, CDCl3) δ 155.02, 135.87, 129.74,
129.24, 125.99, 78.09, 77.55, 77.23, 76.91, 71.25.
4-n-Butyl-1,3-dioxolan-2-one (2b): 1H NMR (400 MHz, CDCl3) δ 4.71 (tt,
J = 7.5, 3.8 Hz, 1H), 4.54 (t, J = 8.1 Hz, 1H), 4.08 (dd, J = 8.4, 7.2 Hz,
1H), 1.92-1.78 (m, 1H), 1.70 (dd, J = 7.0, 2.9 Hz, 1H), 1.39 (dd, J = 8.7,
2.2 Hz, 4H), 0.93 (t, J = 7.0 Hz, 3H); 13C NMR (100.6 MHz, CDCl3) δ
155.13, 77.07, 69.43, 33.57, 26.44, 22.26, 13.81.
Conclusions
4-Methyl-1,3-dioxolan-2-one (2c): 1H NMR (400 MHz, CDCl3) δ 5.03-
4.79 (m, 1H), 4.59 (dt, J = 7.9, 5.3 Hz, 1H), 4.17-3.91 (m, 1H), 1.49 (d, J
= 6.2 Hz, 3H); 13C NMR (100.6 MHz, CDCl3) δ 155.16, 73.71, 70.72,
19.28.
In summary, efficient binary catalysts originating from Zn powder,
DMF and BnBr were developed for CO2 fixation. Active binary
ZnBr2 and [DBDMA]Br, were in situ generated, and presented
good compatibility and high catalytic activity for the coupling
reaction of epoxide and CO2. Various cyclic carbonates were
4-Phenoxymethyl-1,3-dioxolan-2-one (2d): 1H NMR (400 MHz, CDCl3)
δ 7.39-7.27 (t, 2H), 7.02 (t, J = 7.4 Hz, 1H), 6.91 (d, J = 7.9 Hz, 2H),
5.09-4.95 (m, 1H), 4.62 (t, J = 8.4 Hz, 1H), 4.54 (dd, J = 8.5, 5.9 Hz, 1H),
4.24 (dd, J = 10.5, 4.4 Hz, 1H), 4.16 (dd, J = 10.5, 3.6 Hz, 1H); 13C NMR
(100.6 MHz, CDCl3) δ 129.72, 122.05, 114.66, 74.05, 66.94, 66.26.
o
obtained in this catalytic system with good yields at 80 C and 1
bar CO2. These results achieved mark this protocol as a
promising motif of rational design of in situ active catalysts from
simple raw materials for the synthesis of organic carbonate
starting from CO2.
4-(Hydroxymethyl)-1,3-dioxolan-2-one (2e): 1H NMR (CDCl3, 400
MHz): δ 4.75-4.85 (m, 1H), 4.45-4.55 (m, 2H), 3.97 (d, 1H), 3.71 (d, 1H),
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10.1002/ejoc.201801653
European Journal of Organic Chemistry
FULL PAPER
2.50-3.00 (br, 1H); 13C NMR (CDCl3, 100.6 MHz) δ 155.58, 76.79, 65.92,
Bruckmeier, B. Rieger, W. A. Herrmann, F. E. Kühn, Angew. Chem. Int.
Ed. 2011, 50, 8510-8537; e) Z. Sun, H. Tao, Q. Fan, B. Han, Chem
2017, 3, 560–587; f) K. Dong, X.-F. Wu, Angew. Chem., Int. Ed. 2017,
56, 5399-5401; g) A. Banerjee, G. R. Dick, T. Yoshino, M. W. Kanan,
Nature 2016, 531, 215-219; h) J. Schneidewind, R. Adam, W. Baumann,
R. Jackstell, M. Beller, Angew. Chem., Int. Ed. 2017, 56, 1890-1893. i)
X. Liu, X. Li, C. Qiao, H. Fu, L.-N. He, Angew. Chem. Int. Ed. 2017, 56,
7425-7429.
61.75.
1
4-i-Propoxy-1,3-dioxolan-2-one (2f): H NMR (CDCl3, 400 MHz) δ 4.82
(m, 1H), 4.50 (t, J = 8.0 Hz, 1H), 4.38 (dd, J = 8.0 Hz, J= 15.6 Hz, 1H),
3.58-3.70 (m, 3H), 1.16 (d, J = 6.4 Hz, 6H); 13C NMR (CDCl3, 100.6 MHz)
δ 155.18, 75.31, 72.86, 67.11, 66.40, 21.87, 21.76.
[2]
[3]
Selected examples for cyclic carbonate from CO2: a) M. Cokoja, M. E.
Wilhelm, M. H. Anthofer, W. A. Herrmann, F. E. Kuhn, ChemSusChem
2015, 8, 2436-2454; b) L. Longwitz, J. Steinbauer, A. Spannenberg, T.
Werner, ACS Catal. 2018, 8, 665-672; c) J. Steinbauer, T. Werner,
ChemSusChem 2017, 10, 3025-3029; d) H. Büttner, L. Longwitz, J.
Steinbauer, C. Wulf, T. Werner, Top Curr. Chem. 2017, 375, 50; e) X.-B.
Lu, D. J. Darensbourg, Chem. Soc. Rev. 2012, 41, 1462-1484.
Selective catalysts designing for cycloaddition of CO2 and epoxide: a) T.
Ema, Y. Miyazaki, S. Koyama, Y. Yano, T. Sakai, Chem. Commun.
2012, 48, 4489-4491; b) J. Rintjema, R. Epping, G. Fiorani, E. Martín, E.
C. Escudero-Adán, A. W. Kleij, Angew. Chem., Int. Ed. 2016, 55, 3972-
3976; c) C. J. Whiteoak, N. Kielland, V. Laserna, E. C. Escudero-Adán,
E. Martin, A. W. Kleij, J. Am. Chem. Soc. 2013, 135, 1228-1231; d)J.
Langanke, L. Greiner, W. Leitner, Green Chem. 2013, 15, 1173-1182;
e) X.-B. Lu, B. Liang, Y.-J. Zhang, Y.-Z. Tian, Y.-M. Wang, C.-X. Bai, H.
Wang, R. Zhang, J. Am. Chem. Soc. 2004, 126, 3732-3733; f) Z. Wu, H.
Xie, X. Yu, E. Liu, ChemCatChem 2013, 5, 1328-1333; g) Y. Ren, J. J.
Shim, ChemCatChem 2013, 5, 1344-1349; h) M. E. Wilhelm, M. H.
Anthofer, M. Cokoja, I. I. E. Markovits, W. A. Herrmann, F. E. Kuhn,
ChemSusChem 2014, 7, 1357-1360; i) C. J. Whiteoak, A. Nova, F.
Maseras, A. W. Kleij, ChemSusChem 2012, 5, 2032-2038.
4-Chloromethyl-1,3-dioxolan-2-one (2g): 1H NMR (CDCl3, 400 MHz): δ
4.99-5.05 (m, 1H), 4.60 (t, J = 8.4 Hz, 1H), 4.43 (dd, J = 6.0 Hz, 8.4 Hz,
1H), 3.82 (dd, J = 5.2 Hz, 12.0 Hz, 1H), 3.81 (dd, J = 3.2 Hz, 12.0 Hz,
1H); 13C NMR (CDCl3, 100.6 MHz) δ 154.43, 74.43, 66.99, 43.98.
4-((Allyloxy)methyl)-1,3-dioxolan-2-one (2h): 1H NMR (CDCl3, 400
MHz) δ 3.61-3.72 (m, 2H), 4.06-4.07 (m, 2H), 4.39-4.43 (m, 1H), 4.51 (t,
1H), 4.80-4.86 (m, 1H), 5.22-5.32 (m, 2H); 13C NMR (CDCl3, 100.6 MHz)
δ 155.03, 133.76, 118.11, 75.11, 72.74, 68.95, 66.41.
4,4-Dimethyl-1,3-dioxolan-2-one (2i): 1H NMR (CDCl3, 400 MHz): δ
4.17 (s, 2H), 1.53 (s, 6H); 13C NMR (CDCl3, 100.6 MHz) δ 154.65, 81.76,
75.39, 25.98.
Synthesis and characterization of [DBDMA]Br, ZnBr2 and dibenzyl
ether
In a 10 mL Schlenk flask, Zn powder (65.3 mg, 1 mmol), benzyl bromide
(342.1 mg, 2 mmol) and DMF (500 mg) were charged successively at
room temperature. The flask was capped with a stopper and sealed.
Then, the reaction mixture was stirred at 80 oC for 3 h. After the reaction
was completed, the mixture was purified by column chromatography
(silica gel as stationary phase) with ethyl acetate-petroleum ether (1:5) as
the eluent to afford dibenzyl ether (0.22 mmol), and with ethanol as the
eluent to afford [DBDMA]Br and ZnBr2 mixture. After removing ethanol
and adding 1 mL dichloromethane, ZnBr2 (white solid, 0.51 mmol) could
be precipitated out and filtered. And [DBDMA]Br (white solid, 117.0 mg,
0.45 mmol) was obtained by evaporating the dichloromethane solution.
ZnBr2 was characterized by X-ray powder diffraction (Figure S1, JCPDS
#No. 36-0756). The characterization data of dibenzyl ether and
[DBDMA]Br are all in good agreement with literature value.[15,11]
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1
Dibenzyl ether: H NMR (400 MHz, CDCl3) δ 7.36 (d, 8H), 7.26-7.31 (m,
2H), 4.70 (s, 4H); 13C NMR (100.6 MHz, CDCl3) δ 140.99, 128.72, 127.82,
127.13, 65.54.[15]
[DBDMA]Br: 1H NMR (400 MHz, CDCl3) δ 7.68 (m, 4H), 7.44 (m, 6H),
5.18 (s, 4H), 3.14 (s, 6H); 13C NMR (100.6 MHz, CDCl3) δ 133.54, 130.93,
129.39, 127.34, 67.88, 48.41. HRMS (ESI): m/z: calcd for C16H20BrN:
305.0779, [M-Br-]+; found 226.1593.[11]
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Acknowledgements ((optional))
This work was financially supported by Natural Science
Foundation of Shandong Province (ZR2017BB025, J16LC15),
National Natural Science Foundation of China (21472103,
21672119), the Natural Science Foundation of Tianjin
(16JCZDJC39900), and Youth Science and Technology
Innovation Fund of Shandong Agricultural University (24166).
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Keywords: carbon dioxide fixation • C1 building blocks •
atmospheric pressure • cyclic carbonates• Zinc
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10.1002/ejoc.201801653
European Journal of Organic Chemistry
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Entry for the Table of Contents (Please choose one layout)
Key Topic: CO2 Fixation
FULL PAPER
Active catalysts in situ generated
from Zn powder, dimethyl formamide
and benzyl bromide were designed
Shuai Zhang,*[a,b] Feng Han,[b] Shaorui
Yan,[b] Mingyue He, [b] Chengxia
Miao,[b] and Liang-Nian He*[a]
In situ generated
active catalysts
for fixation of CO2 to cyclic
carbonates at 80 oC and atmospheric
pressure of CO2. Zinc bromide and
N,N-dibenzyl-N,N-
Page No. – Page No.
Efficient Catalysts In Situ Generated
from Zinc, Amide and Benzyl
Bromide for Epoxide/CO2 Coupling
Reaction at Atmospheric Pressure
CO2
dimethylammonium bromide, being
proved as active catalyst species,
were in situ generated and
immediately
terminal
converted
epoxides
various
the
to
corresponding carbonates efficiently.
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