Synthesis of formamides containing unsaturated groups by: N -formylation of amines using CO2 with H2

Article abstract of DOI:10.1039/c6gc02243j

Formamides have wide applications in the industry and have been synthesized using CO₂ as a carbon source and H₂ as a reducing agent. However, previous systems required a noble catalyst and high temperature to achieve high efficiency, and the substrate scope was mostly limited to saturated amines. The selective N-formylation of amines containing unsaturated groups using CO₂ and H₂ is challenging because the efficient catalysts for the N-formylation are usually very active for hydrogenation of the unsaturated groups. Herein, we achieved for the first time a selective and efficient N-formylation of amines containing unsaturated groups using CO₂ and H₂ with a Cu(OAc)₂-4-dimethylaminopyridine (DMAP) catalytic system. The substrates were converted to the desired formamides, while the unsaturated groups, such as the carbonyl group, the CC bond, CN bond and the ester group remained. The main reason for the excellent selectivity of the Cu(OAc)₂-DMAP catalytic system was that it was very active for the N-formylation reaction, but was not active for the hydrogenation of the unsaturated groups.

Full text of DOI:10.1039/c6gc02243j

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Synthesis of Formamides Containing Unsaturated Groups by N-
Formylation of Amines using CO2 with H2
Hangyu Liu,ab Qingqing Mei,ab Qingling Xu,*b Jinliang Song,a Huizhen Liu*ab and Buxing Han*ab
Received 00th January 20xx,
Accepted 00th January 20xx
Formamides have wide applications in industry and have been synthesized using CO2 as carbon source and H2 as reducing
agent. However, previous systems required noble catalyst and high temperature to achieve high efficiency, and the substrate
scope was mostly limited to saturated amines. Selective Nꢀformylation of amines containing unsaturated groups using CO2
and H2 is challenging because the efficient catalysts for the Nꢀformylation are usually very active for hydrogenation of the
unsaturated groups. Herein, we firstly achieved the selectively and efficiently Nꢀformylation of amines containing
unsaturated groups using CO2 and H2 using Cu(OAc)2ꢀ4ꢀdimethylaminopyridine (DMAP) catalytic system. The substrates
were converted to the desired formamides, while the unsaturated groups, such as carbonyl group, C=C bond, C≡N bond
and ester group remained. The main reason for the excellent selectivity of the Cu(OAc)2ꢀDMAP catalytic system was that it
was very active for the Nꢀformylation reaction, but was not active for hydrogenation of the unsaturated groups.
DOI: 10.1039/x0xx00000x
www.rsc.org/
So far, the formamides with unsaturated functional group are
generally synthesized by using CO, formic acid or
methylformate as the carbon resources.44ꢀ45 It is interesting to
Introduction
CO2 is an abundant and cheap C1 resource. Conversion of CO2
into valueꢀadded chemicals is an important approach for human
being to participate in global carbon cycle.1ꢀ7 Catalytic
chemical reduction is one of the most efficient routes. Some
valueꢀadded chemicals have been synthesized by chemical
reduction of CO2.8ꢀ18
Formamides are a class of chemicals with widespread
applications in industry as solvents and raw materials for
synthesis of other chemicals.19ꢀ20 Various routes and feedstocks
have been used to synthesize formamides,21ꢀ36 and using CO2 as
a carbon resource and H2 as the reducing reagent is ideal
route.22 Various saturated amines have been prepared using
CO2 and H2 as feedstocks.37ꢀ38 Ding and his coꢀworkers
reported the Nꢀformylation of a series saturated amines with H2
and CO2 catalyzed by ruthenium based homogeneous catalyst at
120 oC.39 Shi et al. found that heterogeneous catalyst palladium
was also active for this kind of reactions at 130 C.40 Various
saturated formamides have also been synthesized using
organosilanes as the reducing reagent and CO2 as carbon
resource.25ꢀ36
The formamides containing unsaturated group are more
desirable in many cases because unsaturated group can be
easily further functionalized to produce useful compounds.41ꢀ42
produce this kind of formamides using CO2 to replace these
carbon resources. Recently, Kobayashi and his coꢀworkers
reported the Nꢀformylation of amines containing unsaturated
group using CO2 as the carbon resource and Ph2SiH2 as the
reducing agent, and a chelating bis(NHC) rhodium complexes
(NHC=Nꢀheterocyclic carbene) was used as the catalysts.46
It is well known that hydrogen is commonly used reducing
agent because it is abundant, economic, nonꢀtoxic, and the only
byproduct is H2O. Nꢀformylation of amine derivatives
containing unsaturated group using CO2 and H2, in which the
unsaturated group remains unreacted, is highly desirable, but is
challenging. One of the main reasons is that CO2 is
thermodynamically very stable and kinetically inert in typical
organic syntheses. So the direct reaction between H2 and CO2
usually requires hash reaction conditions, at which the
o
unsaturated group, such as carbonyl group, C=C bond, C
≡N
bond and ester group, is easily hydrogenated.
In this work, we discovered that CuꢀDMAP (1a) catalytic
system could catalyze this kind of reactions very effectively,
and the unsaturated groups (e.g. carbonyl group, C=C bond, C
≡
N bond and ester group) could be remained. As far as we
known, this is the first work for the synthesis of formamides
containing unsaturated groups by Nꢀformylation of amines
using CO2 with H2.
Results
Compared to precious metal catalysts, abundant and inꢀ
expensive firstꢀrow transition metals, especially Cu, Ni, and Co,
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Table 1. Catalyst screening for the Nꢀformylation of 1ꢀcinnamylpiperazine.[a]
are advantageous for largeꢀscale chemical processes. DMAP is
a useful nucleophilic catalyst for a variety of reactions.43 We
studied the performances of copper salts for the Nꢀformylation
reaction of 1ꢀcinnamylpiperazine
(2a) with or without
additives. Cu(OAc)2 only afforded 20% yield of 3a in the
absence of additive (Table 1, entry 1). DMAP (1a) was the best
additive among those tested and Cu(OAC)2ꢀDMAP catalytic
system could afford 91% yield of 3a in 6 h (Table 1, entry 2).
DABCO (1b, 1,4ꢀdiazabicyclo[2.2.2]octane) and N,N,N',N'ꢀ
tetramethylꢀ1,2ꢀdiaminopropane (1c) were also effective for
promoting the reaction and the yields of 3a were 46% and 38%,
respectively (Table 1, entries 3 and 4). The promoting effect of
4ꢀmethylmorpholine (1d) was poor, and the yield of 3a was
only 28% (Table1, entry 5). 4ꢀMethylpyridine(1e),
tetramethylguanidine
(
1f
)
and
TBD
(
1g
,
1,5,7ꢀ
triazabicyclo[4.4.0]decꢀ5ꢀene) suppressed the reaction and
afforded yields of 3a below 20% (Table 1, entries 6ꢀ8).
Inorganic base potassium isopropoxide
(1h) completely
suppressed the reaction (Table 1, entry 9). The other metal
complexes also exhibited high selectivity for the Nꢀformylation
reaction, while the activity was very low at the reaction
conditions (Table 1, entries 10ꢀ14). Furthermore, the
counterions of the copper salts containing oxygen led to higher
activity (Table 1, entries 2 and 10ꢀ12). Cu(OAc)2ꢀDMAP was
the most active and selective catalytic system, and the yield of
the desired product could be as high as 99% at the optimized
condition (Table 1, entry 15). The higher activity of Cu(OAc)2
attribute to the basicity of OACꢀ and it maybe help to activate
H2 by the interaction of oxygen of OACꢀ with H2. And the
reaction mechanism would be discussed below. In addition, the
yield of the product was very low when only DMAP (1a) was
used without metal catalyst (Table 1, entry 16). It can be known
from Entries 1, 15, 16 that Cu(OAc)2 and DMAP had excellent
synergistic effect for the reaction. No formic acid was detected
without amines that indicated that the Nꢀformylation reaction
catalyzed by Cu(OAc)2ꢀDMAP didn’t involve the
hydrogenation of CO2 to formic acid (Table 1, entry 17) and
this result is consistent with the result reported in the
Metal
Yield
Entry
Additive
Selectivity (%)[c]
precursor
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
CuSO4
(%)[b]
20
91
46
38
28
13
19
6
1
2
None
1a
>99
>99
>99
>99
>99
>99
>99
>99
/
3
1b
1c
4
5
6
1d
1e
7
1f
8
1g
9
1h
1a
0
10
11
12
13
14
15
16
17
18
19
57
17
3
>99
>99
>99
>99
>99
>99
>99
/
Cu(NO3)2
CuCl2
1a
1a
Ni(OAc)2
Co(OAc)2
1a
19
21
99
3
1a
[d]
Cu(OAc)2
None
1a
1a
[e]
Cu(OAc)2
None
1a
None
1a
/
0
/
[f]
Cu(OAc)2
7
>99
literature47. The reaction can
’t occur without Cu(OAc)2 and
[a] Reaction conditions: 1ꢀcinnamylpiperazine 1 mmol, PCO2 = PH2 = 40 atm, metal
precursor 10 mol% based on substrate, additive 2 mmol, THF 1.5 mL, 90 oC, 6 h.
[b] Yield of 3a was determined by GC. [c] Selectivity of 3a was determined by
GC. [d] 9 h. [e] Without amines. [f] 4 MPa CO2 were added firstly, and the
solution stirred 1h. Then discharge the CO2, while adding hydrogen 4 MPa and
stirred 6 hours.
DMAP (Table 1, entry 18). The composition of the gas after
reaction was also checked and only CO2 and H2 were detected.
We also studied the effects of temperature and solvents on the
reaction using Cu(OAc)2ꢀDMAP catalytic system for the Nꢀ
formylation reaction of 1ꢀcinnamylpiperazine (2a), and the
results were listed in Table S1. The yields of the desired
product increased with increasing temperature in the range of
o
o
70 C and 90 C. Toluene THF was the most effective among
the solvents checked.
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Table 2. Cu catalyzed Nꢀformylation of amines containing unsaturated group using CO2
and H2.[a,b,c]
(2ꢀcyanoꢀethyl)ꢀformamide was 31% in 12 h (Table 2, entry 9).
The yield of 4ꢀ(4ꢀacetylphenyl)piperazineꢀ1ꢀcarbaldehyde was
above 70% (Table 2, entries 10).
The above results indicate that Cu(OAc)2ꢀDMAP catalytic
system was highly selective and efficient for the Nꢀformylation
of various amines with unsaturated groups using H2 and CO2.
The efficiency and selectivity of the commonly used catalysts
for the Nꢀformylation reaction of saturated amines40, 48ꢀ50 were
also tested using the Nꢀformylation reaction of 1ꢀ
cinnamylpiperazine (2a) (Table 3). The conversion of 2a could
o
reach 99% at 90 C in 6 h, but almost no desired product 3a
was detected over Pd/Al2O3 (Table 3, entry 1). The similar
result was obtained over Pd/C catalyst. When PdCl2 was used
as the catalyst, the conversion of 2a was 94%, while the
selectivity for 3a was only 3% (Table 3, entry 3). For all the Pd
based catalysts checked, other byproducts such as nꢀ
proplbenzene, piperazine that were from the cleavage of CꢀN
bond were detected (Table 3, entries 1ꢀ3). The performance of
the Ru complexes were also investigated (Table 3, entries 4ꢀ6).
The conversion of 2a was 95%, and the selectivity of 3a, 3a’
and 3a’’ was only 11%, 13% and 11% respectively over
[(C6H5)3P]3Ru(CO)(Cl)H and 65% selectivity of the byproducts
from the cleavage of CꢀN bond was detected (Table 3, entry 4).
At the same reaction condition, the conversion of 2a was 75%
over Ru3(CO)12 and the selectivity of 3a was 33% (Table 3,
entry 5). Similarly, the conversion and selectivity of 3a over
RhCl3 were low (Table 3, entry 7). All the results above
indicate that the noble metal based catalysts, which are
commonly used in the Nꢀformylation reaction of saturated
amines had very poor selectivity for the Nꢀformylation of the
amine containing C=C bond.
[a] Reaction conditions: amine 1 mmol, PCO2 = PH2 = 40 atm, Cu(OAc)2 10 mol%
based on substrate, DMAP 2 mmol, THF (1.5 mL), 90 oC, 12 h. [b] Yield was
determined by GC. [c] Selectivity was determined by GC. [d] 20 h. [e] Yield was
determined by 1H NMR.
The results above indicate that Cu(OAc)2 and DMAP (1a) is an
excellent combination for the Nꢀformylation of 1ꢀ
cinnamylpiperazine. We further explored the formylation of
various amines with different unsaturated groups to examine
the versatility of the catalytic system using H2 as a reductant in
THF, and the results are listed in Table 2. The Nꢀformylation
reaction proceeded smoothly to selectively afford the
corresponding formamides in good to excellent yields, and C=C
bond, carbonyl group and ester group could be remained.
Cu(OAc)2ꢀDMAP catalytic system was effective for piperazine
derivatives. The yield of 4ꢀallylpiperazineꢀ1ꢀcarbaldehyde
could reach 95% in 12 h (Table 2, entry 1). The yield of 1ꢀ
formylꢀ4ꢀacetylpiperazine and 1ꢀBocꢀ4ꢀformylpiperazine were
all above 80% (Table 2, entries 2 and 3). 86% yield of 4ꢀ
benzoylꢀ1ꢀpiperazinecarboxaldehyde was obtained when the
reaction time prolonged to 20 h (Table 2, entry 4). The
reactivity of chain secondary amines that contains C=C bond
was lower than piperazine derivatives with C=C bond (Table 1,
entries 1 and 5ꢀ7). The yield of N,Nꢀdiallylformamide, Nꢀ(2ꢀ
Table 3 The Nꢀformylation of 1ꢀcinnamylpiperazine (2a) over different catalysts
Selectivity (%)
Entr
y
Conversi
on (%)
catalyst
3a
trace
0
3a’
36
47
22
3a’’
48
othersa
16
1
2
3
Pd/Al2O3
Pd/C
>99
>99
94
36
17
PdCl2
3
50
25
[(C6H5)3P]3Ru
(CO)(Cl)H
Ru3(CO)12
RhCl3
4
95
11
13
11
65
5
6
75
77
33
42
7
7
53
58
trace
trace
cyclohexꢀ1ꢀenylꢀethyl)ꢀformamide
and
NꢀmethylꢀNꢀallylꢀ
Reaction conditions: 2a 1 mmol, PCO2=PH2=40 atm, catalyst 10 mol%, THF 1.5
mL, 90 oC, 6 h. Conversion and selectivity was determined by GC, [a] the product
from the cleavage of CꢀN bond.
formamide were 60%, 64% and 83% in 12 h, respectively
(Table 1, entries 5ꢀ7), while 87% yield of Nꢀ(2ꢀcyclohexꢀ1ꢀ
enylꢀethyl)ꢀformamide was obtained when the reaction time
was prolonged to 20 h (Table 2, entry 6). The yield of Nꢀformyl
desloratadine was 83% (Table 2, entry 8). The yield of N,Nꢀbisꢀ
The most interesting part of this work is that Cu(OAc)2ꢀ
DMAP catalytic system was very selective and effective for the
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Table 4. Cu catalyzed Nꢀformylation of amines without unsaturated group using H2 and
CO2.[a,b]
Nꢀformylation reactions of various amines with unsaturated
bond. To investigate the reason for this interesting phenomenon,
we studied its catalytic activity for hydrogenation of a series of
compounds containing different unsaturated bonds and the
results are shown in Figure 1. The catalytic system was not
active for the hydrogenation of the unsaturated bonds ( ꢀC≡N,
C=C, C=O), which can explain reasonably the high selectivity
of Cu(OAc)2ꢀDMAP catalytic system for the Nꢀformylation
reactions. We also used PdCl2 as the catalyst for hydrogenation
of these substrates. (Figure 1) We found that these substrates
converted to the corresponding saturated compounds, which
can explain the low selectivity of noble metal catalytic system
for the Nꢀformylation reactions.
H
O
H
N
Cu(OAc)2+DMAP
H2 + CO2
+
N
R1
R2
R1
R2
Entry
1
Product
Entry
Product
Entry
11
Product
Entry
Product
O
N
H
O
O
O
6
16
N
NH
N
N
H
H
56% (72%c)
99%
99%
90%
H
O
O
H
O
H
N
12
13
17
18
2
3
7
N
N
H
N
H
O
O
72%
54% (80%c)
99%
N
0%
O
O
H
N
O
NH
H
8
N
55% (80%c)
96%
0%
25% (70c)
N
O
O2N
O
19
O
N
N
O
H
N
14
15
4
5
9
O
H
H
85%
99%
0%
90%
H
H
O
Cl
O
O
10
20
N
N
N
NH
H
N
O
H
45% (64%c)
95%
55% (99%c)
0%
[a] Reaction conditions: amine 1 mmol, PCO2 = PH2 = 40 atm, Cu(OAc)2 10 mol%
based on substrate, DMAP 2 mmol, THF 1.5 mL, 90 oC, 12 h. [b] Yield was
determined by GC. [c] 20 h.
To study the reaction mechanism, control experiment was
performed. (Table 1, entry 19) Firstly the reaction of 1ꢀ
cinnamylpiperazine and 4 MPa CO2 was allowed to proceed for
1 h in the presence of Cu(OAc)2ꢀDMAP. The CO2 was
removed and 4 MPa H2 was added and stirred for 6 h, and the
product 3a was also produced, which indicated that CO2 and 1ꢀ
cinnamylpiperazine or DMAP can form the salt51 and the salt
further reacted with hydrogen to the final product.
Figure1. Hydrogenation of the compounds containing various unsaturated bonds with
different catalysts. Reaction conditions: a reactant 1 mmol, PCO2 = PH2 = 40 atm,
Cu(OAc)2 10 mol% based on substrate, DMAP 2 mmol, THF 1.5 mL, 90 oC, 6 h. b
reactant 1 mmol, PCO2 = PH2 = 40 atm, PdCl2 10 mol% based on substrate, THF 1.5 mL,
90 oC, 6 h. Conversion of the reactant was determined by GC.
It has been reported that oxygenꢀcontaining ligands may help
to activate hydrogen.53 Similarly, we got a transition state for
Noble metal based catalysts are commonly used in the Nꢀ OAcꢀ assisted hydrogen cracking through calculation.52(Figure
formylation reaction of saturated amines.37ꢀ40, 48ꢀ50 In this work, S1 in SI) On the basis of the experimental results, the possible
we also studied the catalytic performance of the Cu(OAc)2ꢀ reaction mechanism was proposed for the reaction over
DMAP catalytic system for the Nꢀformylation reaction of Cu(OAc)2ꢀDMAP catalytic system (Figure 2). Amines can react
typical saturated amines , and the results are provided in Table with CO2 to form internal salt very easily.51 Next, the cleavage
−H bond accompanied with the formation of CꢀH bond and
4. It can be known that the catalytic system was also very of H
effective for the Nꢀformylation of saturated amines. The OꢀH bond. And finally H2O was lost and got the final product.
excellent activity of Cu(OA )2ꢀDMAP system results from In order to further illustrate the role of DMAP, the reaction
synergistic effect of Cu(OA
)2 and DMAP for Nꢀformylation solutions with and without DMAP at 50 oC were examined
reactions, as discussed above (Table 1, Entries 1, 15, 16). using UVꢀVis spectroscopy and the spectra were shown in Fig.
c
c
However, the Cu(OAC)2ꢀDMAP catalytic system
3. The absorption peak of copper acetate appears at 696 nm(a).
Without DMAP, the absorption peak was observed at around
579 nm, which are characteristic of coordinate of copper and
amine (b). For the reaction solution with DMAP, the peak shifts
to 667 nm indicated the coordination of copper and DMAP (c).
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Foundation of China (21603235, 21533011, 21321063), and
Chinese Academy of Sciences (KJCX2.YW.H30).
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19 K. Weissermel, H. J. Arpe, Industrial Organic Chemistry, 3rd
ed. Translated by C. R. Lindley, Wiley-VCH, Weinheim, 1997
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9237.
21 M. F. Ali, B. M. El Ali, J. G. Speight, Handbook of Industrial
Chemistry-Organic Chemicals, McGraw-Hill: New York, 2005.
22 A. Tlili, E. Blondiaux, X. Frogneux and T. Cantat, Green Chem.,
2015, 17, 157-168.
23 Y. H. Wang, J. Zhang, H. J. Chen, Z. X. Zhang, C. F. Zhang, M. R.
Li and F. Wang, Green Chem., DOI: 10.1039/c6gc02603f.
In summary, Cu(OAc)2ꢀDMAP catalytic system are very
selective and active for the Nꢀformylation reactions of amines
containing unsaturated groups using H2 and CO2. The
unsaturated groups in the substrates, including carbonyl group,
C=C bond and ester group, are all stable under the reaction
condition. High yields of the desired formamides can be
obtained with selectivity of >99%. However, the selectivity of
the desired product over Pd, Ru and Rh based catalysts, which
are commonly used for the Nꢀformylation reactions of saturated
amines, is very low because the catalysts are also very active
for the hydrogenation of the unsaturated bonds. We believe that
the highly selective, active, and cheaper catalytic system has
great potential of application for producing formamides with
unsaturated groups.
24 Z. G. Ke, Y. Zhang, X. J. Cui and F. Shi, Green Chem., 2016, 18
808-816.
,
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Miyaji and T. Baba, Catal. Sci. Technol., 2013, , 2392-2396.
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26 O. Jacquet, C. D. N. Gomes, M. Ephritikhine and T. Cantat, J.
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27 L. D. Hao, Y. F. Zhao, B. Yu, Z. Z. Yang, H. Y. Zhang, B. X. Han,
Acknowledgements
X. Gao and Z. M. Liu, ACS Catal., 2015, 5, 4989-4993.
This work was supported by the Recruitment Program of 28 C. D. N. Gomes, O. Jacquet, C. Villiers, P. Thuéry, M.
Ephritikhine and T. Cantat, Angew. Chem. Int. Ed., 2012, 51
187-190.
,
Global Youth Experts of China, National Natural Science
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
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ARTICLE
Journal Name
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Int. Ed., 2015, 54, 9209-9212.
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52 See the Supporting Information for the complete references.
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This journal is © The Royal Society of Chemistry 20xx
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Synthesis of Formamides Containing Unsaturated Groups
by N-Formylation of Amines using CO2 with H2
Hangyu Liu, Qingqing Mei, Qingling Xu*, Jinliang Song,
Huizhen Liu* and Buxing Han*
Table of Contents
1. Experimental section.......................................................................S2
2. Optimization of conditions…………………………….…..............S3
3. Characterization data for the Nꢀformylation products......................S4
4. Cartesian coordinate and energy of TS at the B3LYP /6ꢀ31G*
level..................................................................................................S9
5. Full citation of Gaussian program...................................................S11
6. References………………………...................................................S11
1

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1. Experimental section
Chemicals
4ꢀdimethylaminopyridine, DBACO, TMG, potassium tertꢀbutoxide,
4ꢀmethylpyridine, 4ꢀmethylmorpholine, tetramethylethylenediamine, PdCl2,
Chloroformꢀd,
1ꢀallylpiperazine,
3,3'ꢀIMinodipropionitrile,
diallylamine,
4'ꢀpiperazinoacetophenone,
1ꢀacetylpiperazine,
2ꢀ(1ꢀcyclohexenyl)ethylamine,
1ꢀBocꢀpiperazine,
Nꢀallylmethylamine,
1ꢀbenzoylpiperazine, 1,2,3,4ꢀtetrahydroisoquinoline, benzonitrile, αꢀAl2O3,
1ꢀphenylꢀ1ꢀpropyne, pyrrolidine, Nꢀethylpiperazine, butylamine, dibutylamine,
4ꢀmethylpiperidine, dihexylamine, nꢀoctylamine, cyclohexylamine, morpholine,
1ꢀmethylpiperazine, cyclohexene, styrene, nꢀdecane and tetrahydrofuran were
purchased
from
J&K
Scientific
Ltd.
Cu(OAc)2,
1,5,7ꢀtriazabicyclo[4.4.0]decꢀ5ꢀene, RhCl3, desloratadine, benzylamine,
dibenzylamine,
Nꢀmethylbenzylamine
Transꢀ1ꢀcinnamylpiperazine,
hexamethyleneimine,
Nꢀmethylbutylamine
by Energy
and
Chemical.
Pd/C,
was provided
carbonylchlorohydridotris(triphenylphosphine)ruthenium(II) and Ru3(CO)12
purchased from alfa aesar. CuSO4•5H2O, Cu(NO3)2•3H2O, CuCl2•2H2O,
Ni(OAc)2•4H2O, Co(OAc)2•4H2O, nitrobenzene, cyclohexanone and sodium
tetrahydroborate was provided by Sinopharm Chemical Reagent Co., Ltd. The
CO2 (99.99%), H2 (99.99%) and N2 (99.99%) were provided by Beijing
Analytical Instrument Company.
Characterization
1H and 13C Nuclear Magnetic Resonance (NMR) spectra were recorded on a
1
Bruker Avance III HD 400 MHz NMR spectrometer (400 MHz for H and 100
MHz for 13C) at ambient temperature in CDCl3. GC/MS analysis was conducted
on Agilent 7890B GC+ 5977 MSD. Sample analysis was operated on an
Agilent 6820 gas chromatography equipped with a flame ionization detector
(FID) and a HPꢀ5 capillary column (30 m × 0.25 mm × 0.25 ꢁm), Agilent
Technologies Singapore (Sales) Pte Ltd., Singapore.
N-Formylation of amines using H2 and CO2
The reaction was carried out in a Teflonꢀlined stainlessꢀsteel reactor of 10 mL in
capacity with a magnetic stirrer. The pressure was determined by a pressure
transducer (FOXBORO/ICT, Model 93), which could be accurate to ±0.025
MPa. In a typical experiment, 0.1 mmol of Cu(OAc)2 and 2 mmol of
4ꢀdimethylaminopyridine (DMAP) were loaded into the reactor. 1 mmol of
substrate and 1.5 mL solvent (e.g. THF) were added. The reactor was sealed
and purged with H2 to remove the air at ambient temperature. The reactor was
placed in an air bath at desired temperature. H2 of 40 atm was added, and then
CO2 was charged until the total pressure reached 80 atm, and then the stirrer
was started at 500 rpm. After reaction the reactor was placed in ice water and
the gas was released. The reaction mixture was analyzed by GCꢀMS and GC
with decane as an internal standard, or purified by flash column
2

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chromatography on silica gel to afford the desired product was characterized by
1H NMR and 13C NMR.
Prepare of Pd/Al2O3
Suitable amount of H2PdCl4 (8 mg) were added into 50 mL distilled water and
400 mg αꢀAl2O3 was added to the solution under stirring. A freshly prepared
solution of NaBH4 (0.1 M, 20 mL) was then added under stirring to form a dark
o
solution. After the mixture was further stirred for 3 h at 30 C, it was
centrifuged and washed by water, dried at 120 oC for 4 h and calcined at 350 oC
for 4 h in air. A grey solid sample was obtained.s1
Compution
The geometrical optimizations TS were performed at the 6ꢀ31G* level. All
calculations were performed with the Gaussian 09 programs. Frequencies were
calculated at the same level to confirm each stationary point to be either a
minimum (no imaginary frequency) or a saddle point (unique imaginary
frequency).
2. Optimization of reaction conditions
Table S1 Optimization of condition for the catalytic Nꢀformylation reaction of
1ꢀcinnamylpiperazinea
T
Cu(OAc)2
(mol%)b
Entry
Solvent
DMAP (equiv)b
Yield (%)c
(oC)
1
2
3
4
5
6
7
8
70
80
90
90
90
THF
THF
10
10
10
10
10
10
10
10
2
2
2
2
2
2
2
2
2
51
91
0
THF
water
toluene
85
61
53
83
90 cyclohexane
90 acetonitrile
90 1,4ꢀdioxane
3

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9
90
90
90
90
90
ethanol
THF
10
5
2
2
3
10
11
12
13
67
33
25
16
THF
2
2
THF
10
10
1
THF
0.5
aReaction conditions: transꢀ1ꢀcinnamylpiperazine (1 mmol), PCO2=PH2= 40 atm,
b
solvent (1.5 mL), 6 h. The amount based on the substrate, cYield of 3a was
determined by GC.
3. Characterization data for the N-formylation products
1
4ꢀcinnamylpiperazineꢀ1ꢀcarbaldehyde: H NMR (CDCl3, 400 MHz) δ 8.02 (s, 1H),
7.38ꢀ7.21 (m, 5H), 6.56ꢀ6.51 (m, 1H), 6.27ꢀ6.20 (m, 1H), 3.59ꢀ3.56 (t, J =5.1 Hz, 2H),
3.40ꢀ3.37 (t, J =5.1 Hz, 2H), 3.18ꢀ3.16 (m, 2H), 2.51ꢀ2.45 (m, 4H). 13C NMR (CDCl3,
100 MHz) δ160.52, 136.47, 133.33, 128.42, 127.49, 126.15, 125.65, 60.70, 53.28,
52.17 45.44, 39.77.
1
4ꢀallylpiperazineꢀ1ꢀcarbaldehyde: H NMR (CDCl3, 400 MHz) δ 8.03 (s, 1H),
5.89ꢀ5.79 (m, 1H), 5.23ꢀ5.17 (m, 2H), 3.59ꢀ3.56 (t, J =5.1 Hz, 2H), 3.40ꢀ3.38 (t, J
=5.1 Hz, 2H), 3.04ꢀ3.01 (t, J =5.5 Hz, 2H), 2.47ꢀ2.44 (t, J = 5.1 Hz, 2H), 2.43ꢀ2.41 (t,
J = 5.2 Hz, 2H). 13C NMR (CDCl3, 100 MHz) δ160.67, 134.35, 118.45, 61.53, 53.33,
52.20, 45.60, 39.93.
N,Nꢀdiallylcarboxamide:1H NMR (CDCl3,400 MHz) δ 8.13 (s, 1H), 5.79ꢀ5.66 (m,
2H), 5.26ꢀ5.14 (m, 4H), 3.95ꢀ3.94 (m, 2H), 3.83ꢀ3.81 (m, 2H). 13C NMR (CDCl3,100
MHz) δ162.51, 133.10, 132.12, 118.55, 118.08, 58.44, 49.25, 44.32.
4

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Nꢀ(2ꢀcyclohexꢀ1ꢀenylꢀethyl)ꢀformamide:1H NMR (CDCl3,400 MHz) δ 8.16 (s, 0.79H),
8.06ꢀ7.97 (m, 0.21H), 5.49 (s, 1.72H), 5.30 (s, 0.24H), 3.40ꢀ3.27 (m, 2H),2.17ꢀ2.13 (s,
2H), 2.01ꢀ2.00 (s, 2H), 1.93ꢀ1.91 (m, 2H), 1.66ꢀ1.52 (m, 4H). 13C NMR (CDCl3,100
MHz) δ164.35, 161.07, 134.23, 133.20, 124.63, 123.64, 37.35, 35.72, 28.00, 27.75,
25.12, 25.08, 22.69, 22.66, 22.22, 22.15.
1
NꢀmethylꢀNꢀallylꢀformamide: H NMR (CDCl3,400 MHz) δ 8.08 (s, 1H), 5.79ꢀ5.69
(m, 1H), 5.30ꢀ5.18 (m, 2H), 3.96ꢀ3.94 (d, J= 6.0Hz, 1H), 3.84ꢀ3.82(d, J= 5.7Hz, 1H),
2.91(s, 1H), 2.84 (s, 2H). 13C NMR (CDCl3, 100 MHz) δ162.67, 132.87, 131.86,
118.45, 118.06, 51.98, 46.61, 33.96, 29.45.
Nꢀformyl desloratadine: 1H NMR (CDCl3,400 MHz) δ8.39ꢀ8.36 (m, 1H), 8.06 (s, 1H),
7.42 (s, 1H),7.16ꢀ7.0 (m, 4H),3.35ꢀ3.20 (m, 2H),3.1ꢀ3.0 (m, 2H),2.9ꢀ2.6 (m,
4H),2.3ꢀ2.4 (m, 4H).
1
4ꢀbenzoylꢀ1ꢀpiperazinecarboxaldehyde: H NMR (CDCl3, 400 MHz) δ 8.08 (s, 1H),
7.41 (m, 5H), 3.73ꢀ3.40 (m, 8H).13C NMR (CDCl3, 100 MHz) δ 169.24, 159.82,
134.03, 128.87, 127.43, 125.85, 44.20, 38.69.
1
1ꢀformylꢀ4ꢀacetylpiperazine: H NMR (CDCl3, 400 MHz) δ 8.09 (s, 1H), 3.63ꢀ3.36
(m, 8H), 2.13 (s, 3H). 13C NMR (CDCl3, 100 MHz) δ168.542, 160.37, 160.29, 46.13,
44.99, 44.89, 44.47, 41.23, 40.07, 39.37, 20.70.
5

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1ꢀBocꢀ4ꢀformylpiperazine: 1HNMR (CDCl3, 400 MHz) δ8.08 (s, 1H), 3.53ꢀ3.35 (m, 8
H), 1.48 (s, 9H). 13C NMR (CDCl3,100 MHz) δ160.69, 154.20, 80.25, 45.24, 39.75,
28.17.
1
4ꢀ(4ꢀacetylphenyl)piperazineꢀ1ꢀcarbaldehyde: H NMR (CDCl3, 400 MHz) δ 8.10 (s,
1H), 7.84 (d, J = 8.70 Hz, 2H), 6.86 (d, J =8.70 Hz, 2H), 3.64 (t, J = 5.04 Hz, 2H),
3.49 (t, J = 5.52, 2H), 3.30 (dt, J = 17.06, 5.21 Hz, 4H), 2.48 (s, 3H). 13C NMR
(CDCl3, 100 MHz) δ 195.91, 160.55, 153.40, 129.99, 127.80, 113.85, 48.01, 46.77,
44.56, 39.16, 25.84.
1
N,Nꢀbisꢀ(2ꢀcyanoꢀethyl)ꢀformamide: HNMR (CDCl3, 400 MHz) δ8.23 (s, 1H),
3.72ꢀ3.66 (m, 4 H), 2.78ꢀ2.68 (m, 4H). 13C NMR (CDCl3, 100 MHz) δ163.07, 117.90,
117.39, 44.33, 43.66, 15.96.
N,Nꢀdibenzylformamide:1H NMR (CDCl3, 400 MHz) δ 8.54 (s, 1H), 7.43ꢀ7.26 (m,
10H), 4.51 (s, 2H), 4.33 (s, 2H). 13C NMR (CDCl3, 100 MHz) δ 161.24, 134.60,
134.31, 127.27, 127.08, 126.73, 126.62, 126.17, 125.99,48.51, 42.93.
1
Nꢀbenzylformamide: H NMR (400 MHz, CDCl3)δ8.23 (s, 1H), 8.15 (d, J = 11.9 Hz,
1H), 7.21ꢀ7.40 (m, 5H), 6.07 (s, 1H), 4.46 (d, J = 5.9 Hz, 2H), 4.39 (d, J = 6.5 Hz,
2H).13C NMR (100 MHz, CDCl3) δ 161.07, 160.83 , 137.71, 128.8, 128.6, 127.6,
127.5, 127.0, 45.7, 41.9
6

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1
NꢀbenzylꢀNꢀmethylformamide: H NMR (400 MHz, CDCl3)δ 8.29ꢀ8.16 (m, 1H),
7.39ꢀ7.19 (m, 5H), 4.51ꢀ4.37 (m, 2H), 2.82ꢀ2.76 (m, 3H).13C NMR (100 MHz,CDCl3)
δ 161.55, 161.40, 135.02,134.84, 127.68, 127.50, 127.40, 126.98, 126.82, 126.40,
126.31, 52.12, 46.44, 32.83, 28.15.
3,4ꢀdihydroꢀ2(1H)ꢀisoquinolinecarbaldehyde: 1H NMR (CDCl3, 400 MHz) δ 8.21 and
8.16 (m,1H), 7.16ꢀ7.08 (d,J=30.8 Hz, 4H), 4.63ꢀ4.48(m,2H), 3.73ꢀ3.59 (m, 2H), 2.85
(s, 2H). 13C NMR (CDCl3, 100 MHz) δ160.83, 160.33, 133.55, 132.86, 131.58,
130.96, 128.32, 128.18, 126.25, 125.87, 125.75, 125.69, 125.16, 46.43, 42.38, 41.44,
37.16, 28.90, 27.13.
1
Nꢀformylpyrrolidine: H NMR (400 MHz, CDCl3) δ 8.22 (s, 1H),3.46ꢀ3.38 (d, J =
13
30.2 Hz,4H), 2.00ꢀ1.88 (m, 4H); CNMR (100 MHz, CDCl3) δ 159.97, 45.19, 42.28,
24.10, 23.42.
1
1ꢀ(formyl)ꢀhexahydroꢀ1Hꢀazepine: H NMR (400 MHz, CDCl3) δ 8.05 (s, 1H),
3.41ꢀ3.33 (d, J = 31.3 Hz, 4H), 1.68 (s, 4H), 1.53 (s, 4H).13C NMR (100 MHz, CDCl3)
δ 161.49, 46.36, 42.05, 28.99, 26.72, 25.64, 25.59.
1
4ꢀmethylꢀ1ꢀformylpiperidine: H NMR (400 MHz, CDCl3) δ 7.99 (s, 1H), 4.33ꢀ4.30
(m, 1H),3.57ꢀ3.54 (m, 1H), 3.01 (s, 1H),2.59 (s, 1H), 1.65ꢀ1.62 (m, 3H), 1.18ꢀ1.03 (m,
2H), 0.93 (s, 3H).13C NMR (100 MHz, CDCl3) δ159.41, 44.78, 38.54, 33.42, 32.03,
29.93, 20.44.
7

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Nꢀformylmorpholine: 1H NMR (400 MHz, CDCl3) δ8.05 (s, 1H), 3.70ꢀ3.68 (t, J = 4.9
Hz, 2H), 3.66ꢀ3.64 (t, J = 4.9 Hz, 2H), 3.57ꢀ3.54 (t, J = 4.9Hz, 2H), 3.43ꢀ3.40 (t, J =
4.9 Hz, 2H).13C NMR (100 MHz,CDCl3) δ 160.31, 66.68, 65.84,45.22, 40.02.
1
4ꢀformylꢀ1ꢀmethylpiperazine: H NMR (400 MHz, CDCl3) δ 7.99 (s, 1H), 3.54 (s,
2H), 3.36 (s, 2H), 2.44 – 2.35 (m, 7H). 13C NMR (100 MHz, CDCl3) δ 159.90, 52.43,
51.47, 44.84, 43.72, 39.17.
4ꢀethylꢀ1ꢀformylpiperazine: 1H NMR (400 MHz, CDCl3) δ 8.01 (s, 1H), 3.52 (s, 2H),
3.36 (s, 2H), 2.39ꢀ2.35 (m, 6H), 1.06 (m, 3H).13C NMR (100 MHz, CDCl3) δ 159.24,
51.77, 50.77, 50.58, 44.12, 38.45, 10.57.
1
N,Nꢀdibutylformamide: H NMR (400 MHz,CDCl3) δ 8.04 (s, 1H)3.29ꢀ3.27 (t, J =
5.8 Hz, 2H), 3.20ꢀ3.18 (t, J = 5.8 Hz, 2H),1.51 (s, 4H),1.32ꢀ1.29 (m, 4H), 0.94ꢀ0.92
(m, 6H). 13C NMR (100 MHz, CDCl3) δ161.76, 46.26, 40.94, 29.85, 28.52, 19.26,
18.74, 12.93, 12.77.
N,Nꢀdihexylformamide:1H NMR (400 MHz, CDCl3) δ 8.03 (s, 1H), 3.28 (t, J=6.4 Hz,
2H), 3.18 (t, J=6.9 Hz, 2H), 1.52 (s, 4H), 1.29 (s, 12H), 0.89 (m, 6H).13C NMR (100
MHz, CDCl3) δ 162.7, 47.4, 42.1, 31.5, 31.4, 28.6, 27.3, 26.6, 26.1, 22.6, 22.5, 14.0,
14.0.
1
NꢀbutylꢀNꢀmethylformamide: H NMR (400 MHz,CDCl3) δ 8.03 (s, 1H),3.33ꢀ3.29(t,
8

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DOI: 10.1039/C6GC02243J
J = 6.0 Hz, 0.55H), 3.23ꢀ3.19 (t, J = 6.0 Hz,1.22H),2.91 (s, 1.0H), 2.83 (s, 2H),
1.52ꢀ1.50(m,2H), 1.29ꢀ1.26 (m, 2H), 0.94ꢀ0.91 (t, J = 5.8 Hz, 3H).13C NMR (100
MHz,CDCl3) δ161.71, 161.58, 48.38, 42.95, 33.65, 29.17, 27.88, 18.62, 17.87, 12.97,
12.81.
H
O
NH
1
Nꢀbutylformamide: H NMR (400 MHz, CDCl3) δ 8.30ꢀ7.91 (m, 1H), 5.78 (s, 1H),
3.44ꢀ3.07 (m, 2H), 1.59ꢀ1.45 (m, 2H), 1.43ꢀ1.28 (m, 2H), 0.94 (m, 3H).13C NMR (100
MHz, CDCl3) δ 160.77, 46.17, 39.94, 34.71, 33.27, 31.36, 21.72.
H
O
NH
Nꢀoctylformamide:1H NMR (400 MHz, CDCl3) δ 8.30ꢀ7.91 (m, 1H), 5.53 (d, J =
149.5 Hz, 1H), 3.25 (m, 2H), 1.49 (m, 2H), 1.29 (d, J = 10.8 Hz, 9H), 0.88 (t, J = 6.6
Hz, 3H). 13C NMR (100 MHz, CDCl3) δ 164.57, 161.13, 77.35, 77.03, 76.71, 41.75,
38.20, 31.70, 31.65, 31.24, 29.52, 28.88, 28.78, 26.79, 26.34, 22.54, 14.01.
H
O
HN
1
Nꢀcyclohexylformamide: H NMR (400 MHz, CDCl3) δ 8.09(s, 1H),5.54 (br, 1H),
5.89ꢀ5.29 (m, 1H), 3.96ꢀ2.75 (m, 1H), 1.99ꢀ1.85 (m, 2H), 1.80ꢀ1.57 (m, 3H), 1.44
ꢀ1.25 (m, 3H), 1.24ꢀ1.09 (m, 2H). 13C NMR (100 MHz, CDCl3) δ 163.50, 160.26,
50.93, 47.09, 34.71, 33.05, 25.43, 25.04, 24.73.
4. Cartesian coordinate and energy of transition state at the
B3LYP /6-31G* level
Figure S1. transition state for OAcꢀ assisted hydrogen cracking
9

Green Chemistry
Page 16 of 17
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DOI: 10.1039/C6GC02243J
transition state:
Standard orientation:
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
Center
Number
Atomic
Number
Atomic
Type
Coordinates (Angstroms)
X
Y
Z
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
1
2
3
4
5
6
7
8
9
29
6
6
6
1
6
1
6
1
1
7
7
6
1
1
1
6
1
1
1
8
8
6
6
8
8
6
1
1
1
6
1
1
1
8
6
8
6
ꢀ0.000001973
0.000001992
0.000001368
ꢀ0.000000197
0.000000133
ꢀ0.000001612
ꢀ0.000001339
ꢀ0.000000846
0.000000720
ꢀ0.000002099
ꢀ0.000002182
ꢀ0.000000838
ꢀ0.000001081
ꢀ0.000000856
ꢀ0.000004655
ꢀ0.000003318
ꢀ0.000004350
ꢀ0.000003232
ꢀ0.000002581
ꢀ0.000002360
ꢀ0.000002261
ꢀ0.000002808
0.000004730
0.000002118
0.000002708
0.000003388
0.000000449
0.000001940
0.000003548
0.000003233
0.000003629
0.000003882
0.000002519
0.000004657
0.000002472
0.000004299
ꢀ0.000001457
ꢀ0.000000551
ꢀ0.000000449
ꢀ0.000000399
0.000000099 ꢀ0.000000167
0.000000135 ꢀ0.000000061
0.000000000 ꢀ0.000000759
0.000000181 ꢀ0.000000981
0.000000058 ꢀ0.000000270
0.000000015
0.000000237
ꢀ0.000000012 ꢀ0.000001221
ꢀ0.000000004 ꢀ0.000000963
ꢀ0.000000042 ꢀ0.000000183
0.000000407
0.000000170
ꢀ0.000000324 ꢀ0.000001761
ꢀ0.000000610 ꢀ0.000000791
ꢀ0.000000352 ꢀ0.000001494
0.000000693 ꢀ0.000001890
ꢀ0.000000338 ꢀ0.000000788
ꢀ0.000000306 ꢀ0.000000312
0.000000130 ꢀ0.000000903
ꢀ0.000000222 ꢀ0.000000717
ꢀ0.000000090
0.000001619 ꢀ0.000000227
ꢀ0.000000292 ꢀ0.000001767
ꢀ0.000000951
ꢀ0.000000487 ꢀ0.000001105
0.000000759 0.000001016
0.000001677 ꢀ0.000001432
0.000001739 ꢀ0.000002061
0.000001679 ꢀ0.000001587
0.000001467 ꢀ0.000001405
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
ꢀ0.000000615
0.000000338
0.000000809
0.000001360
ꢀ0.000000211
0.000001133
0.000000402
ꢀ0.000000606
0.000000231
ꢀ0.000002127 ꢀ0.000000186
0.000001384 ꢀ0.000002630
ꢀ0.000000679
0.000001208
0.000000214
0.000001723
0.000002043
0.000000408
0.000001421
10

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Green Chemistry
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DOI: 10.1039/C6GC02243J
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
6
6
1
6
1
1
1
7
8
1
1
1
1
1
1
0.000000250 ꢀ0.000000334
ꢀ0.000000501
ꢀ0.000000903
ꢀ0.000000593
ꢀ0.000000353
0.000001866
0.000001367
0.000000298
ꢀ0.000001095
0.000000549
ꢀ0.000001671
ꢀ0.000001057
ꢀ0.000001693
ꢀ0.000001898
0.000000585
ꢀ0.000001379
ꢀ0.000000780
0.000000083
ꢀ0.000000260
ꢀ0.000002246
0.000003684
0.000001354
0.000000130 ꢀ0.000000626
ꢀ0.000001199
ꢀ0.000000393
ꢀ0.000002332
ꢀ0.000000836
ꢀ0.000001306
ꢀ0.000000854
0.000001993
0.000000046
0.000001254
0.000001411
0.000002587
0.000001973
ꢀ0.000000025 ꢀ0.000000200
ꢀ0.000000610 0.000000440
ꢀ0.000001034 ꢀ0.000003186
0.000005707 0.000004617
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
SCFꢀ Energy:B3LYP (PCM, THF)/6ꢀ31G* = ꢀ2956.149565 (a.u.)
5. Full citation of Gaussian program (Reference 44 details)
Gaussian 09, Revision A.1, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson,
H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida,
T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E.
Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N.
Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S.
S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B.
Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V.
G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels,
Ö. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian, Inc.,
Wallingford CT, 2009.
6. References
S1
.
X. J. Cui, Y. Zhang, Y. Q. Deng and F. Shi, Chem. Commun., 2014, 50,
189ꢀ191.
S2. M. Cossi, G. Scalmani, N. Rega, V. Barone, J. Chem. Phys., 2002, 117, 43ꢀ54.
11