Quaternary ammonium hydroxide as a metal-free and halogen-free catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide

Article abstract of DOI:10.1039/c5cy00020c

Tetrabutylammonium hydroxide (TBAH) and other quaternary ammonium hydroxides catalyzed the cycloaddition of CO₂ to epoxides under solvent-free conditions to give cyclic carbonates. When TBAH was exposed to CO₂, TBAH was converted into tetrabutylammonium bicarbonate (TBABC), which was a catalytically active species. A D-labeled epoxide and an optically active epoxide were used to study the reaction mechanism, which invoked three plausible pathways. Among them, path A seemed to be predominant; the bicarbonate ion of TBABC attacks the less hindered C atom of the epoxide to generate a ring-opened alkoxide intermediate, which adds to CO₂ to give a carbonate ion, and the subsequent cyclization yields a cyclic carbonate. Density functional theory (DFT) calculations successfully delineated the potential energy profile for each reaction pathway, among which path A was the lowest-energy pathway in accordance with the experimental results. The tetrabutylammonium (TBA) cation carries the positive charges on the H atoms, but not on the central N atom, and the positively charged H atoms close to the central N atom form an anion-binding site capable of stabilizing various anionic transition states and intermediates.

Full text of DOI:10.1039/c5cy00020c

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Quaternary ammonium hydroxide as a metal-free
and halogen-free catalyst for the synthesis of
cyclic carbonates from epoxides and carbon
dioxide†
Cite this: DOI: 10.1039/c5cy00020c
a
a
a
b
c
Tadashi Ema,* Kazuki Fukuhara, Takashi Sakai,* Masaki Ohbo, Fu-Quan Bai‡
and Jun-ya Hasegawa*b
Tetrabutylammonium hydroxide (TBAH) and other quaternary ammonium hydroxides catalyzed the
cycloaddition of CO to epoxides under solvent-free conditions to give cyclic carbonates. When TBAH was
exposed to CO , TBAH was converted into tetrabutylammonium bicarbonate (TBABC), which was a catalyt-
2
2
ically active species. A D-labeled epoxide and an optically active epoxide were used to study the reaction
mechanism, which invoked three plausible pathways. Among them, path A seemed to be predominant; the
bicarbonate ion of TBABC attacks the less hindered C atom of the epoxide to generate a ring-opened
2
alkoxide intermediate, which adds to CO to give a carbonate ion, and the subsequent cyclization yields a
Received 7th January 2015,
Accepted 26th January 2015
cyclic carbonate. Density functional theory (DFT) calculations successfully delineated the potential energy
profile for each reaction pathway, among which path A was the lowest-energy pathway in accordance
with the experimental results. The tetrabutylammonium (TBA) cation carries the positive charges on the
H atoms, but not on the central N atom, and the positively charged H atoms close to the central N atom
form an anion-binding site capable of stabilizing various anionic transition states and intermediates.
DOI: 10.1039/c5cy00020c
www.rsc.org/catalysis
phosgene, which is highly toxic, and by the concomitant pro-
duction of hydrogen chloride and waste solvent. This is why
Introduction
Synthesis of useful compounds from carbon dioxide (CO ) is
many catalysts for the production of cyclic carbonates from
2
1
,2
an important subject in synthetic organic chemistry.
Among various methods for CO fixation, the catalytic synthe-
CO and epoxides have been developed, such as alkali metal
2
3
4
5
6
2
salts, metal complexes, salen complexes, ionic liquids,
organocatalysts, quaternary ammonium salts, and immo-
bilized catalysts. Some of them, however, have problems,
7
8
sis of cyclic carbonates from CO2 and epoxides has been
extensively studied. Cyclic carbonates are used as monomers
for polycarbonates, electrolytes for lithium-ion batteries, and
polar aprotic solvents. Although some of them have been syn-
thesized from 1,2-diols and phosgene on an industrial scale,
this method has serious environmental loads caused by
9
such as the use of organic solvent and co-catalysts, the forma-
tion of by-products, and the corrosion of reactor vessels.
We have developed quaternary phosphonium salts immo-
10
bilized on mesoporous silica, quaternary ammonium beta-
1
1
ine organocatalysts, and metalloporphyrins bearing quater-
1
2
a
nary ammonium bromide groups. In screening various
quaternary onium salts, we found that tetrabutylammonium
hydroxide (TBAH) showed much higher catalytic activity and
selectivity than expected. Because catalysts for this particular
reaction need a good leaving ability as well as high nucleo-
philicity, TBAH is considered to be unsuitable because of
Division of Chemistry and Biotechnology, Graduate School of Natural Science
and Technology, Okayama University, Tsushima, Okayama 700–8530, Japan.
E-mail: ema@cc.okayama-u.ac.jp
b
Catalysis Research Center, Hokkaido University, Kita 21, Nishi 10, Kita-ku,
Sapporo 001–0021, Japan. E-mail: hasegawa@cat.hokudai.ac.jp
c
Fukui Institute for Fundamental Chemistry, Kyoto University,
34–4 Takano-Nishihiraki, Sakyo, Kyoto 606–8103, Japan
−
the poor leaving ability of the hydroxide ion (OH ). TBAH
†
Electronic supplementary information (ESI) available: Synthesis of cyclic
carbonates from epoxides and CO
2
.
Atomic coordinates of the optimized
has been used as a co-catalyst together with Co salen-type
5a
structures along path A. Comparison between α and β attacks in the initial ring-
opening step. Optimized structures along paths B and C. See DOI: 10.1039/
c5cy00020c
catalysts, and DABCO-type quaternary ammonium hydroxides
13
have been employed as a catalyst. However, no detailed studies
have been reported. In view of the metal-free, halogen-free,
and solvent-free reaction promoted by a simple and inexpen-
sive reagent such as TBAH, we decided to investigate the
‡
Present address: State Key Laboratory of Theoretical and Computational
Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun,
30023, China.
1
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catalytic behavior of TBAH in detail. In particular, a halogen-
free system is required because the use of halogen sometimes
colors a product and corrodes a reactor made of metal. Herein
we report the reaction mechanism of the TBAH-catalyzed syn-
thesis of cyclic carbonates from epoxides and CO2.
products were obtained (entries 7 and 8). These results indi-
cate that the quaternary ammonium cation plays a vital role
1
2c
in catalysis as revealed recently. Tributylamine, which may
be generated by the Hofmann degradation of TBAH, gave 2a
in 13% (entry 9). Even when the catalyst loading of TBAH was
decreased to 0.5 mol%, 2a was obtained in 76% yield (entry 10),
which was slightly lower than the yield (84%) obtained with
tetrabutylammonium bromide (TBAB) (entry 11).
Results and discussion
We examined various quaternary ammonium hydroxides. A
commercially available solution of quaternary ammonium
hydroxide in MeOH was evaporated to dryness to afford a
powder in most cases, which was used as a catalyst. A 30 mL
stainless autoclave was charged with 1,2-epoxyhexane (1a)
We next optimized the reaction conditions. The best
amount of TBAH was 1 mol%, and 2a was obtained in 100%
yield (entry 12). When temperature was changed from 60 to
140 °C in the presence of 1 mol% TBAH, the highest yield
was achieved at 120 °C (entries 12–16). Fig. 1 shows the
time course of the reaction under the optimized conditions
(10.0 mmol), a catalyst, and CO2 (initial pressure, 1 MPa),
and the mixture was heated at a constant temperature for
2
(catalyst loading, 1 mol%; CO pressure, 1 MPa; and 120 °C).
2
2
4 h. The results are summarized in Table 1. Cyclic carbonate
The reaction proceeded smoothly for 3 h, and the yield
increased gradually over 24 h. The substrate scope of the
TBAH-catalyzed reaction was investigated under the opti-
mized conditions (Table 2). Various epoxides were selectively
and cleanly converted into the corresponding cyclic carbon-
ates in moderate to high yields, and no by-products such as
1,2-diol were detected. The products with the electron-
withdrawing groups were obtained in good to excellent yields
(entries 3, 5, 9, and 10). Cyclohexene oxide (1f) reacted with
a was obtained with TBAH in 94% yield (entry 1). In sharp
+
−
4
contrast, Me N OH , which is less bulky than TBAH, gave 2a
in only 2% yield (entry 2). This is probably due to the
poor solubility of Me N OH in epoxide 1a. When choline
+
−
4
+
−
+
−
hydroxide IJHOCH
used, the yields increased up to 55% and 96%, respectively
entries 3 and 4). In general, the bulkier the quaternary
ammonium cation, the higher the nucleophilicity of the
2 2 3 3
CH N Me OH ) and BnN Me OH were
(
1
4
counter anion. However, the hexyl group, which is bulkier
than the butyl group, decreased the catalytic activity (entry 5).
The reaction with tetrabutylphosphonium hydroxide gave 2a
in 22% yield (entry 6). When KOH and NaOH were used, no
CO to afford 2f in high yield (entry 6), whereas epoxide 1g
2
with a five-membered ring was converted into 2g in modest
yield (entry 7). The substrate bearing the t-Bu group gave the
product in moderate yield (entry 8).
Scheme 1 shows two representative mechanisms. In path
−
1
, a nucleophile (Nu ) attacks the epoxide to produce an
Table
1
Screening of catalysts and optimization of the reaction
alkoxide ion, which adds to CO to give a carbonate ion. The
2
a
conditions
subsequent cyclization yields the product. In path 2, on the
other hand, a carbonate ion is first produced, which then
attacks the epoxide to generate an alkoxide ion. The five-
membered ring formation gives a cyclic carbonate. The trans
and cis cyclic carbonates are obtained via paths 1 and 2,
respectively, starting from the trans epoxide (Scheme 1). Soft
1
2
b
nucleophiles often promote the reactions via path 1, while
Catalyst
(mol%)
Temp.
(°C)
Yield
(%)
Entry
Catalyst
hard nucleophiles, such as N-heterocyclic carbenes and
9
b,11
+
−
−
quaternary ammonium betaines,
promote the reactions
1
2
3
4
Bu
Me
HOCH
4
N OH (TBAH)
3
3
3
3
3
3
3
3
120
120
120
120
120
120
120
120
120
120
120
120
140
100
80
94
2
55
96
41
22
0
+
via path 2. On the other hand, TBAH is not simple because
hydroxide has good nucleophilicity and yet a poor leaving
ability, and the TBAH-catalyzed reaction may proceed via
path 2 because hydroxide is a hard anion.
4
N OH
CH
+
−
2
2
N Me
3
OH
+
−
BnN Me
3
OH
c
+
−
d
5
Hex
4
N OH
+
−
6
7
8
9
Bu
4
P OH
NaOH
KOH
To clarify the reaction mechanism, we used deuterated
1
5
0
trans epoxide 1k (Scheme 2). The reaction via path 1 would
give trans-2k, while that via path 2 would afford cis-2k. When
the reaction was carried out under the optimized conditions,
trans-2k and cis-2k were obtained in a ratio of 89 : 11. This
result suggests that the reaction proceeds mainly via path 1
contrary to our expectation. However, as mentioned above,
it is inappropriate to conclude that the reaction proceeds via
Bu
3
N
3
13
76
84
100
86
85
45
22
10
11
12
13
14
15
16
TBAH
0.5
0.5
1
1
1
+
−
4
Bu N Br (TBAB)
TBAH
TBAH
TBAH
TBAH
TBAH
1
1
60
−
path 1 because OH is a poor leaving group. It is more
a
Conditions: epoxide 1a (10.0 mmol), catalyst (amount indicated
b
reasonable to assume the in situ formation of tetrabutyl-
above), CO (1 MPa) in a 30 mL stainless autoclave. Determined by
2
1
c
ammonium bicarbonate (TBABC) (Scheme 3) because the
H NMR using 2-methoxynaphthalene as an internal standard. 10%
d
−
in MeOH. Dimethyl carbonate (7%) as a by-product.
bicarbonate ion IJHCO
3
) is a good nucleophile with a high
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Fig. 1 Time course of the formation of 2a from 1a (10.0 mmol)
and CO
2
(1 MPa) with TBAH (1 mol%) at 120 °C in a 30 mL stainless
autoclave.
leaving ability. In the literature, TBABC was generated by
bubbling CO gas into a solution of TBAH in MeOH for
0 min. The catalytic activity of TBABC was unknown,
2
Scheme 1 Two typical reaction mechanisms for the synthesis of
cyclic carbonates from epoxides and CO .
2
1
6
1
although tetrabutylammonium methylcarbonate was used as
a co-catalyst in the CoIJsalen)-catalyzed reaction of the
1
7
epoxide with CO
1
tive): 61 for HCO
2
.
We therefore prepared TBABC [IR (KBr):
previously been converted selectively into (R)-2d in the
−
1
13
12a,18
653 cm ; C NMR (d -DMSO): 155 ppm; MS (FAB, nega-
literature,
TBAH gave (R)-2d and (S)-2d in a ratio of
6
−
16
] according to the literature method and
87 : 13. This result indicates that the reaction was partially
accompanied by the inversion of configuration to give (S)-2d,
which is inaccessible from both path 1 and path 2.
Based on the above results (Schemes 2 and 4 and DFT
calculations), we considered four reaction pathways shown in
Scheme 5, where the reactions are represented by using a
deuterated (2R)-trans epoxide to clearly distinguish each reac-
tion pathway. Path A involves the double inversion processes
as follows: a bicarbonate ion attacks the less hindered C
atom of the epoxide to produce an alkoxide intermediate,
3
used TBABC as a catalyst instead of TBAH under the reaction
conditions shown in Table 1 (entry 1), obtaining 2a in 89%.
DFT calculations indicated that the formation of TBABC
Scheme 3) is very exothermic (−49.0 kcal mol ) with no acti-
vation barrier. These results strongly suggest that TBABC gen-
erated in situ is a catalytically active species, which prompted
us to explore other pathways similar to path 1, assuming the
formation of TBABC. We further investigated the mechanism
of the TBAH-catalyzed reaction from the viewpoint of stereo-
chemistry using (R)-1d (Scheme 4). Although (R)-1d has
−
1
(
which adds to CO to give a carbonate ion. The subsequent
2
cyclization affords a (4R)-trans cyclic carbonate. Path B
branches from path A; the intramolecular proton transfer
followed by cyclization gives a configurationally inverted
product, a (4S)-trans cyclic carbonate. Because only path B
Table 2 Synthesis of various cyclic carbonates with TBAHa
1
2
b
Entry
1
R
R
Yield (%)
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1f
1g
1h
1i
Bu
H
H
H
H
H
89
66
90
88
74
65
42
53
68
94
Me
CH
Ph
OMe
Cl
Scheme 2 Investigation of the reaction mechanism by using a
D-labeled epoxide.
2
CH
2
–IJCH
–IJCH
t-Bu
CH
CH
2
)
)
4
–
2
3
–
H
H
H
2
Oi-Pr
10
1j
2
OPh
a
2
Conditions: epoxide (10.0 mmol), TBAH (1 mol%), CO (1 MPa) in
b
a 30 mL stainless autoclave. Isolated yield.
2
Scheme 3 In situ formation of TBABC from TBAH and CO .
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profiles for the TBABC-catalyzed reactions of propylene oxide
(
1b) with CO2 are shown in Fig. 2, and the optimized
structures are given in Fig. 3. Fig. 4 represents the electro-
static properties of the tetrabutylammonium (TBA) cation
and tributylamine for comparison. The TBA cation carries
the positive charges on the H atoms, but not on the central
N atom (Fig. 4a), and the positively charged H atoms
close to the central N atom form a flexible anion-binding
site, which is well represented by the large positive area
Scheme
optically pure epoxide.
4 Investigation of the reaction mechanism by using an
1
2c
of the isoelectrostatic potential surface (Fig. 4b).
In con-
trast, the neutral counterpart, tributylamine, has no such
positive regions (Fig. 4b). The initial ring-opening reaction
(
R → TS_1 → I_1), which is common to all the paths, takes
−
1
place with an activation energy of 25.9 kcal mol , and this
is the rate-determining step because of the highest energy
level.
1
2c
−1
The resulting intermediate I_1 is 15.8 kcal mol
higher in energy than reactant R. The optimized structures
with atomic charges for R, TS_1, and I_1 are shown in
Fig. 3a–c. The negative charges in R are located in the bicar-
bonate moiety, and one of the negatively charged O atoms
occupies the anion-binding site of the TBA cation. A small
portion of the negative charge in R migrates to the epoxide
in TS_1, and the charge of the leaving O atom becomes −0.95
in I_1. As seen in Fig. 3c, this negatively charged O atom is
out of the anion-binding site. Therefore, I_1 changes into
more stable intermediate I_1′, where the negatively charged
O atom is located at the anion-binding site. This relaxation
−
1
results in a stabilization of 10 kcal mol (Fig. 3d), which
clearly indicates the significant contribution of the TBA
1
2c
cation to the stabilization of the anionic species.
In path A, the ring-opened intermediate I_1′ accepts CO2
at the negatively charged O atom to generate intermediate
−
1
I_2, which is about 30 kcal mol lower in energy than I_1′.
This substantial stabilization originates from the C–O bond
formation and the delocalization of the negative charge over
the carbonate moiety (the resonance effect). Although TS_2
−
1
was found at −4.3 kcal mol (Fig. 3e), a precursor complex
prior to TS_2 could not be found probably because of the
very small activation energy for TS_2. The negative charges
in intermediate I_2 shift to the leaving bicarbonate moiety
in TS_3 (Fig. 3f and g), and the ring is closed with an acti-
Scheme
5
Possible reaction pathways for the TBABC-catalyzed
, where a
formation of cyclic carbonates from epoxides and CO
deuterated (2R)-trans epoxide is used to clearly distinguish each
reaction pathway.
2
−1
vation energy of 20.2 kcal mol to afford product P. The
−
1
relative potential energy of P is −36.9 kcal mol . The nega-
tively charged bicarbonate ion in P is located at the anion-
binding site of the TBA moiety, and the cyclic carbonate
produced is also stabilized by the TBA moiety (Fig. 3h).
Path B is derived from intermediate I_2 (Fig. 2). Each
structure in path B is given in Fig. S2 (ESI†). The C–O bond
gives the (4S)-product (Scheme 5), (S)-2d in Scheme 4 was
produced probably via path B. Path C also branches from
path A; the intramolecular attack of the alkoxide O atom on
the carbonyl C atom affords a (4R)-cis cyclic carbonate.
Because only path C gives the cis product (Scheme 5), cis-2k
in Scheme 2 may have been formed via path C. Path D, which
is initiated by the α attack, was ruled out by density func-
tional theory (DFT) calculations (Fig. S1, ESI†). Because it is
only path A that gives the (4R)-trans product, it is most likely
that path A is predominant.
rotation in the OCO H moiety of I_2′ leads to intermediate
2
I_3b via TS_3b, and the proton of the OCO
2
H moiety of I_3b
−
is transferred to the OCO
2
moiety to give intermediate I_4b
1
9
via TS_4b. This proton transfer occurs with a very small
−
1
activation barrier (1.5 kcal mol ). Subsequently, the ring-
closing reaction takes place with an activation energy of
−
1
We performed DFT calculations to gain a deeper insight
into the reaction mechanism.
35.1 kcal mol , which is much larger than that of path A
6
g,7c,8e,20
−1
The potential energy
(20.2 kcal mol ). This unfavorable ring-closure in path B
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Fig. 2 Potential energy profiles for the TBABC-catalyzed reactions of propylene oxide (1b) with CO
2
. Computations were performed at
the ωB97XD/6-31G* level with the self-consistent reaction field (SCRF) method (Et
shown in parenthesis in kilocalories per mole. The energy of an isolated CO is included in the epoxide ring-opening step even if CO
not appear explicitly. Paths A, B, C, and C′ are shown in red, blue, black, and purple, respectively. The TBA cation is omitted from the structures.
2
O). The relative potential energies based on reactant R are
2
2
does
Fig. 3 Optimized structures of (a) reactant R, (b) transition state TS_1, (c) intermediates I_1, (d) I_1′, (e) TS_2, (f) I_2, and (g) TS_3, and (h) product
P in the TBABC-catalyzed reaction of propylene oxide (1b) with CO (path A).
2
results from the nucleophilic attack at the sterically hindered
secondary C atom. In addition, the leaving bicarbonate group
stays a little far from the TBA cation in path B. The positions
of the leaving bicarbonate in both cases (paths A and B) are
compared in Fig. S3 (ESI†). The bicarbonate ion in path B is
outside the electrostatic isosurface of +0.1 au, while that in
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Fig. 4 Electrostatic properties of the TBA cation (left) and tributylamine (right) calculated at the ωB97XD/6-31G* level. (a) The natural atomic
charges. The charges at the equivalent atoms are averaged. (b) The isoelectrostatic potential represented by two orthogonal slices. The units are
−
1
given in atomic unit. At the +0.10 au, a −1 point-charge gains a coulombic stabilization of 63 kcal mol . Three of the four anion-binding sites in
the TBA cation are shown in pink circles.
path A is partially inside the surface of +0.1 au. The bicar-
bonate ion in P_b shifts to a more stable position to yield
product P.
succeeding pathways determine the selectivity of the whole
reaction (product distribution). Paths A and B are more favor-
able than paths C and C′ because in the former cases, I_1′
Path C is derived from intermediate I_1′ (Fig. 2). Each
structure in path C is given in Fig. S4 (ESI†). The C–C bond is
rotated with an activation energy of 4.0 kcal mol (TS_2c).
The negatively charged O atom in I_2c attacks the carbonyl C
falls into an energy trough in the presence of CO
2
. Path A is
the most favorable because path A has a much smaller activa-
−
1
−1
−1
tion energy (20.2 kcal mol ) than path B (35.1 kcal mol ).
The reaction can also proceed via path C′ as a minor path-
way. These predictions are consistent with the experimental
results shown in Schemes 2 and 4. Although the reaction
rates may depend not only on the energy levels of the transi-
atom of the OCO H moiety to form a five-membered ring
2
(
I_3c). This ring-closing reaction occurs with a very small acti-
−
1
vation energy (1.5 kcal mol for TS_3c). On the other
hand, there is a larger barrier (15.4 kcal mol ) for I_3c to
release OH . This is because the C–O σ-bond is broken,
−
1
tion states but also on the diffusion efficiency of CO , the
observed selectivity can be well explained based on the
former in this case.
2
−
which can be partially compensated by a C–O π-bond forma-
−
tion, and because the poor leaving group, OH , with a local-
−
ized negative charge is released. The OH ion, which stays at
Conclusions
the anion-binding site of TBA in intermediate I_4c, then
reacts with an extra CO2 molecule to form the bicarbonate
ion and product P_c. The bicarbonate ion in P_c shifts to a
more stable position to give product P. Interestingly, we
Carbon dioxide (CO ) is expected to be an important renew-
2
able feedstock for various useful organic compounds. The
synthesis of cyclic carbonates from epoxides and CO under
2
found a much lower-energy process (path C′), where the
solvent-free conditions is one of the most atom-efficient CO2
fixation methods. Here we have demonstrated that TBAH
is a metal-free and halogen-free organocatalyst suitable for
this reaction. The halogen-free system may find practical
applications because the use of halogen sometimes colors a
product and corrodes a reactor made of metal. Upon expo-
−
leaving OH group in I_3c′, a complex of I_3c with CO
2
, is
to give off a bicarbonate ion
Fig. 2). This step requires a much smaller activation energy
directly transferred to CO
2
(
(
−
1
7.7 kcal mol ).
Fig. 2 indicates that the reaction mechanisms are not
straightforward. However, because all the reaction pathways
paths A–C′) have common intermediate, I_1′, the
sure to CO , TBAH is converted into tetrabutylammonium
bicarbonate (TBABC), which is a catalytically active species.
2
(
a
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Two experiments using a D-labeled epoxide and an optically Acknowledgements
active epoxide revealed that three paths, A–C, proceeded
This work was supported by the Okayama Foundation for
Science and Technology. NMR spectra were measured at the
SC-NMR Laboratory of Okayama University. Computations
were partly carried out at RCCS (Okazaki, Japan) and ACCMS
competitively, among which path A was likely to be the
most favorable. Density functional theory (DFT) calculations
successfully delineated the potential energy profile for each
reaction pathway. The tetrabutylammonium (TBA) cation
carries the positive charges on the H atoms, but not on
the central N atom, and the positively charged H atoms
close to the central N atom form an anion-binding site that
can stabilize various anionic transition states and intermedi-
ates. The lowest-energy process was confirmed to be path A
in accordance with the experimental results. The rate-
determining step was the initial ring-opening reaction of
the epoxide by TBABC, and the subsequent CO2 addition
and cyclization gave a cyclic carbonate with the regeneration
of TBABC.
(
Kyoto University).
Notes and references
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Commun., 2012, 48, 9956–9964; (c) N. Kielland, C. J. Whiteoak
and A. W. Kleij, Adv. Synth. Catal., 2013, 355, 2115–2138; (d)
C. Maeda, Y. Miyazaki and T. Ema, Catal. Sci. Technol.,
2
014, 4, 1482–1497; (e) C. Martín, G. Fiorani and A. W. Kleij,
ACS Catal., 2015, 5, 1353–1370.
Experimental section
Synthesis of 4-deuterio-5-octyl-1,3-dioxolan-2-one
2
(a) K. Nakano, T. Kamada and K. Nozaki, Angew. Chem., Int.
Ed., 2006, 45, 7274–7277; (b) F. Goettmann, A. Thomas and
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A 30 mL stainless autoclave was charged with trans-1-
15
(
2
c) Y. Kayaki, M. Yamamoto and T. Ikariya, J. Org. Chem.,
007, 72, 647–649; (d) S. Minakata, I. Sasaki and T. Ide,
deuterio-1,2-epoxydecane (1k) (1.58 g, 10.0 mmol), TBAH
26.7 mg, 1 mol%), and then CO (initial pressure, 1 MPa at
(
2
Angew. Chem., Int. Ed., 2010, 49, 1309–1311; (e) Y. Takeda,
S. Okumura, S. Tone, I. Sasaki and S. Minakata, Org. Lett.,
room temperature). The mixture was heated with stirring
at 120 °C for 24 h. The reactor was cooled in an ice bath for
2
012, 14, 4874–4877; ( f ) S. Kikuchi, K. Sekine, T. Ishida and
2
0 min, and excess CO2 was released carefully. The crude
T. Yamada, Angew. Chem., Int. Ed., 2012, 51, 6989–6992; (g)
N. Ishida, Y. Shimamoto and M. Murakami, Angew. Chem.,
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and S. Ma, Org. Lett., 2013, 15, 977–979; (i) T. Mita, J. Chen
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Y. Zhao, H. Zhang, J. Xu, L. Hao, X. Gao and Z. Liu, Chem.
Commun., 2014, 50, 2330–2333; (k) Q.-W. Song, B. Yu,
X.-D. Li, R. Ma, Z.-F. Diao, R.-G. Li, W. Li and L.-N. He,
Green Chem., 2014, 16, 1633–1638; (l) Y.-B. Wang, D.-S. Sun,
H. Zhou, W.-Z. Zhang and X.-B. Lu, Green Chem., 2014, 16,
product was dissolved in Et O. The NMR yield was deter-
mined by using 2-methoxynaphthalene as an internal stan-
dard. Purification by silica gel column chromatography
2
(hexane/EtOAc (7 : 1)) gave a mixture of trans- and cis-4-
deuterio-5-octyl-1,3-dioxolan-2-one (87%, trans : cis = 89 : 11)
as a colorless oil. trans-4-Deuterio-5-octyl-1,3-dioxolan-2-one.
1
3
H NMR (CDCl , 300 MHz) δ 0.88 (t, J = 6.7 Hz, 3H), 1.27–1.48
(
7
1
m, 12H), 1.62–1.72 (m, 1H), 1.75–1.85 (m, 1H), 4.05 (d, J =
.2 Hz, 1H), 4.70 (q, J = 6.7 Hz, 1H); C NMR (CDCl3,
00 MHz) δ 14.1, 22.6, 24.4, 29.10, 29.13, 29.3, 31.8, 33.9, 69.2
1
3
2
266–2272; (m) T. Fujihara, Y. Horimoto, T. Mizoe,
(
1
t, J = 23.4 Hz), 77.1, 155.2; IR (neat) 2928, 2857, 1802, 1466,
−
1
F. B. Sayyed, Y. Tani, J. Terao, S. Sakaki and Y. Tsuji, Org.
Lett., 2014, 16, 4960–4963.
(a) N. Kihara, N. Hara and T. Endo, J. Org. Chem., 1993, 58,
368, 1169, 1065, 773, 714 cm ; HRMS (EI) calcd. for
+
11 3
C H19DO : 201.1475, found 201.1460 ([M ]). cis-4-Deuterio-5-
octyl-1,3-dioxolan-2-one. H NMR (CDCl
(
1
1
2
1
3
4
3
, 300 MHz) δ 0.88
6
1
198–6202; (b) K. Kasuga and N. Kabata, Inorg. Chim. Acta,
997, 257, 277–278.
t, J = 6.7 Hz, 3H), 1.27–1.48 (m, 12H), 1.62–1.72 (m, 1H),
.75–1.85 (m, 1H), 4.51 (d, J = 7.4 Hz, 1H), 4.70 (q, J = 6.7 Hz,
1
3
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H. G. Jang, Chem. – Eur. J., 2003, 9, 678–686; (b) S.-F. Yin
and S. Shimada, Chem. Commun., 2009, 1136–1138; (c)
M. M. Dharman, J.-I. Yu, J.-Y. Ahn and D.-W. Park, Green
Chem., 2009, 11, 1754–1757; (d) P. Ramidi, S. Z. Sullivan,
Y. Gartia, P. Munshi, W. O. Griffin, J. A. Darsey, A. Biswas,
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H); C NMR (CDCl
3
, 100 MHz) δ 14.1, 22.6, 24.4, 29.10,
9.13, 29.3, 31.8, 33.9, 69.1 (t, J = 23.2 Hz), 77.1, 155.2.
Computational details
All the computations were done with Gaussian 09. Density
functional theory (DFT) calculations at the ωB97XD /6-31G*
level were carried out to obtain the optimized structures
and the potential energies. The solvation effect was included
with the self-consistent reaction field (SCRF) method, and
the dielectric constant of Et O was used. Natural population
analysis (NPA) was performed with NBO ver 3.1 in the
Gaussian package. The transition-state structures were
verified by frequency calculations.
2
1
2
2
2
3
2
2
4
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