Zinc Powder Catalysed Formylation and Urealation of Amines Using CO2 as a C1 Building Block?

Article abstract of DOI:10.1002/cjoc.202000072

Transformation of CO₂ into valuable organic compounds catalysed by cheap and biocompatible metal catalysts is one of important topics of current organic synthesis and catalysis. Herein, we report the zinc powder catalysed formylation and urealation of amines with CO₂ and (EtO)₃SiH under solvent free condition. Using 2 molpercent zinc powder as the catalyst, a series of secondary amines, both the aromatic ones and the aliphatic ones, can be formylated into formamides. When primary aromatic amines were used as the substrates, the reactions produce urea derivatives. The electronic and steric effects from the substrates on the formylation and urealation reactions were observed and discussed. The recovery and reusability of zinc powder were investigated, showing the zinc powder can be reused in the formylation reaction without loss of catalytic activity. The analysis on the reactants/products mixture after filtering out the zinc powder showed the zinc concentration in the mixture is low to 1 ppm. The pathways for the formylation and urealation of amines with this catalytic system were also investigated, and related to the different substrates.

Full text of DOI:10.1002/cjoc.202000072

Chinese Journal
of Chemistry
CJC
中 国 化 学 - An International Journal
Accepted Article
Title: Zinc Powder Catalysed Formylation and Urealation of Amines using CO2 as C1
Building Block
Authors: Chongyang Du, and Yaofeng Chen*
This manuscript has been accepted and appears as an Accepted Article online.
This work may now be cited as: Chin. J. Chem. 2020, 38, 10.1002/cjoc.202000072.
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Chinese Journal
of Chemistry
Amine, Carbon Dioxide, Formylation, Urealation, Zinc
Report
CJC
中
国 化 学 - An International Journal
Zinc Powder Catalysed Formylation and Urealation of Amines using CO2
as C1 Building Block
Chongyang Du, and Yaofeng Chen*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy
of Sciences, 345 Lingling Road, Shanghai 200032, P. R. China
Cite this paper:Chin. J. Chem.2019,37, XXX—XXX.DOI: 10.1002/cjoc.201900XXX
Summary of main observation and conclusion Transformation of CO2 into valuable organic compounds catalysed by cheap and biocompatible metal
catalysts is one of important topics of current organic synthesis and catalysis. Herein, we report the zinc powder catalysed formylation and urealation of
amines with CO2 and (EtO)3SiH under solvent free condition. Using 2mol% zinc powder as the catalyst, a series of secondary amines, both the
aromaticones and the aliphatic ones, can be formylated into formamides. When primary aromatic amines used as the substrates, the reactions produce
urea derivatives. The electronic and steric effects from the substrates on the formylation and urealation reactions were observed and discussed. The
recovery and reusability of zinc powder were investigated, showing the zinc powder can be reused in the formylation reaction without loss of catalytic
activity. The analysis on the mixture of reactants and products after the reaction showed the zinc concentration is low to 1 ppm. The pathways for the
formylation and urealation of amines with this catalytic system were also investigated, and related to the different substrates.
conditions.[24] However, silylamines are less accessible compared
to primary amines, and actuallysilylamines are generally
synthesised from primary amines with n-BuLi and Me3SiCl.
Background and Originality Content
Due to its abundance, availability, nontoxicity and recyclability,
the use of CO2 as one-carbon (C1) building block in organic
Polymer-immobilized gold nanoparticle catalysts are able to
synthesis has received a great attentions.[1] In the last decade,
catalyse the urealation of cyclohexylamine and benzylamine with
many procedures have been developed for the CO2 chemical
CO2 in good yields under high CO2 pressure (50 atm) and at high
fixation via the construction of C-C, C-O or C-N bonds.[2]
N-formylation of CO2 and amines plays an important role in the
CO2 fixation, as the reaction products, formamides, have many
applications in organic synthesis.[3] Hence, researchers have
devoted many efforts to develop efficient catalytic catalysts for
such transformation, and various metal catalysts including Cu,[4]
Pd,[5] Ru,[6] Fe,[7] Co,[8] Rh,[9] Ni,[10] Au,[11] and alkali-metal
complexes (or salts),[12] have been used in the N-formylation of
CO2 and amines. Some metal-free catalysts such as carbenes,[13]
ionic liquids,[14] tetrabutylammonium fluoride (TBAF) and glycine
betaine (GB),[15] dimethyl sulfoxide (DMSO),[16] (BH3NH3),[17] and
temperature (180 °C).[25] CsOH in ionic liquids[26] and Cs2CO3 or
CeO2 in N-metylpyrrolidone[27] also catalyse the urealation of
aliphatic amines with CO2 to produce the corresponding urea
derivatives in good yields, but when aromatic amines are used as
the substrates, the yields of the products are very low or even no
products are formed. A combination of CeO2 with 2-cyanopyridine
can increase the catalytic activity to aniline, but no other aromatic
amines were investigated.[27b] Very recently, [Fe3(CO)12] catalysed
urealation of amine with CO2 in the presence of PhSiH3 was
reported, but only one substrate, benzylamine, was
investigated.[28]
1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]-pyrimidine
(TBD)[18]
As an abundant, biocompatible and environmentally friendly
metal, zinc complexes (or salts) have been utilized in many
interesting and important stoichiometric and catalytic reactions.[29]
In recent years, the groups of Wehmschulte, Parkin, Okuda,
Dagorne and us found that zinc complexes are able to catalyse
CO2 hydrosilylation, providing silylformate, bis-(silylacetal),
methoxysilane or methane.[30] Meanwhile, Cantat and co-workers
reported the first example of zinc complexes catalysed
methylation of amines with CO2 and hydrosilanes.[31] By using
N-heterocyclic carbene (NHC)-supported ZnCl2 as the catalyst and
PhSiH3 as the reductant, a variety of primary and secondary
aromatic amines are methylated. Later, Ji and co-workers
developed the cooperative catalytic systems composed of
Zn(salen) catalysts and quaternary ammonium salts or the
were also reported for the N-formylation of CO2 and amines.
Urea derivatives have the important applications in polymer
synthesis, chemical analysis and biological studiesas well as in
pharmaceuticals and agrochemicals.[1,19] Synthesis of urea
derivatives from CO2 and amines is of interests. It has been
reported that reactions of primary amines with CO2 give urea
derivatives, but the reactions require harsh conditions[20] or the
presence of stoichiometric amounts of bases such as NEt3,[21]
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU),[22] and pyridine.[23] In
addition, due to the thermodynamic equilibrium of the reactions,
large
amounts
of
dehydrating
agents,
such
as
and
dicyclohexylcarbodiimide,[21]
Me3NSO3,[22]
diphenylphosphite,[23] are needed. Reactions of silylamines with
CO2 provide a way to synthesise urea derivatives under mild
bifunctional
Zn(salen)
complexes
containing
two
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imidazolium-based ionic-liquid units at the 3,3’-position of salen
ligand, which catalyse the formylation of amines with CO2 and
PhSiH3 under mild conditions.[32] Herein, we reported the
formylation and urealation of amines with CO2 and inexpensive
(EtO)3SiH catalysed by the cheap and reusable zinc powder.
7
8
1.5
1.5
1.5
1.5
1.5
120
120
120
120
120
18
12
24
24
24
88
82
79
75
73
-
84
80
75
-
9c
10d
11e
Results and Discussion
The formylation of N-methylaniline (1a) with CO2 using
(EtO)3SiH as the reductant under different reaction conditions
was investigated (Table 1). Firstly, the reactions were carried out
with 2.4 equivalents of (EtO)3SiH under 1.5 MPa pressure of CO2
using 2 mol% of Zn powder (Aladdin company, 99.99% purity, 600
mesh) as the catalyst for 24 h, and no solvent was used. At 30 oC,
no formylation of N-methylaniline occurs (entry 1), and narrowly
the disproportionation of (EtO)3SiH. When the reaction
temperature rises to 100 oC (entry 2), the formylation of
N-methylaniline occurs, the conversion of 1a reaches 77% and the
yield of N-methyl-N-phenylformamide (2a) is 70%. The conversion
of 1a and the yield of 2a are improved to 92% and 86%
a Reaction conditions: 1a (5 mmol), (EtO)3SiH (12 mmol), Zn powder (0.1
b
mmol). Determined by quantitative 1H NMR using mesitylene as an
e
internal standard. c 0.05 mmol Zn powder. d 0.025 mmol Zn powder.
Without Zn powder.
The reactions of N-methylaniline (1a) catalysed by Zn powders
from other companies and with different sizes were also
investigated (Table 2, entries 1-3). Under same reaction
conditions, all the reactions provide the formylation product
N-methyl-N-phenylformamide (2a) in high yields. We also used 2
mol% of copper or iron power instead of zinc power. For the
reaction with copper powder, no formylation occurs; for the
reaction with iron powder, the yield of 2a is about 24% (entries 4
and 5). The reaction in the presence of ZnCl2 or ZnO was also
studied. When 2 mol% of ZnCl2 is used, the conversion of 1a is
57%, the yield of 2a is only 19% (entry 6), the main product is N,
N-dimethylaniline. This is similar to the literature result.[31] When
2 mol% of ZnO is used, the yield of 2a is 11% (entry 7). A small
amount of Zn powders is formed during the reaction, this newly
formed Zn powders may catalyse the formylation of 1a. Therefore,
the reaction solution is carefully removed, and the reactants are
added to this ZnO/Zn mixture for the next run under the same
reaction conditions. As expected, the yield of 2a increases. The
yields of 2a for the 2nd and 3rd runs are 50% and 73%,
respectively (entries 8 and 9). This is in consistent with an
increasing of Zn powder for the 2nd and 3rd runs.
o
respectively when the reaction temperature increases to 120 C
o
(entry 3). Further increasing the reaction temperature to 140 C,
the conversion of 1a is same, but the yield of 2a decreases to 74%
o
(entry 4). The lower yield of 2a at 140 C is due to the further
reduction of 2a into N, N-dimethylamine (6%, observed from the
quantitative 1H NMR spectrum). The reaction is also influenced by
the CO2 pressure. At 120 oC, the conversion of 1a and the yield of
2a both decrease when decreasing the CO2 pressure. The reaction
under 1 MPa CO2 provides 87% conversion of 1a and 78% yield of
2a, and the reaction under 0.5 MPa CO2 provides 80% conversion
of 1a and 69% yield of 2a. It should be noted that the by-product,
N, N-dimethylamine, increases when decreasing the CO2 pressure.
The effects of the reaction time were also studied. The
conversions of 1a decrease to 88% and 84% for 18 and 12 h,
respectively, and accordingly the yields of 2a are 82% and 79%.
Reducing the Zn powder loading to 1 mol% or 0.5 mol%, the
reaction still occurs, but the conversion of 1a and the yield of 2a
become lower (entries 9 and 10). Without Zn powder as the
catalyst, the formylation does not occur (entry 11). When
polymethylhydrosiloxane(PMHS) or H2 is used as the reductant
instead of (EtO)3SiH, the formylation does not occur.
Table 2 Formylation of N-methylaniline (1a) with CO2 and (EtO)3SiH
catalyzed by metal powder, ZnCl2 or ZnO.a
Purity
(%)
Gram.
(mesh)
Conv. of
1ab (%)
Yield of
2ab (%)
Entry
Cat.
Source
1
2
3
Zn
Zn
Zn
Aladdin
Alfa Aesar
Aldrich
99.99
99.9
> 98
600
100
92
86
88
86
83
84
Table 1 Formylation of N-methylaniline (1a) with CO2 and (EtO)3SiH
catalysed by Zn powder.a
1340
Energy
Chemical
CO2 pres.
(MPa)
Temp.
(oC)
Time
(h)
Conv. of
Yield of
Entry
4
Cu
99
300
0
0
1ab (%)
2ab (%)
5
6
Fe
Aladdin
TCI
AR
100
-
24
57
24
19
1
2
3
4
5
6
1.5
1.5
1.5
1.5
1.0
0.5
30
24
24
24
24
24
24
-
-
ZnCl2
> 98
100
120
140
120
120
77
92
92
87
80
70
86
74
78
69
7
ZnO
Alfa Aesar
99
-
11 (1st)
11
8
9
ZnO
ZnO
Alfa Aesar
Alfa Aesar
99
99
-
-
50 (2nd)
75 (3rd)
50
73
a Reaction conditions: 1a (5 mmol), (EtO)3SiH (12 mmol), metal powder or
metal salt (0.1 mmol), 1.5 MPa CO2, 120 oC, 24 h. Determined by
b
quantitative 1H NMR using mesitylene as an internal standard.
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Running title
Chin. J. Chem.
Under the reaction conditions of 2.4 equivalents (EtO)3SiH,
1.5 MPa CO2, 2 mol% of Zn powder and 120 C, the scope of
powder (0.1 mmol), 120 oC, 24 h, solvent free, isolated yield. b The NMR
spectrum showed no consumption of N-methyl (p-nitroaniline). c Reaction
for 48 h.
o
amines was subsequently investigated. A series of N-methyl
aromatic amines were formylated for 24 h, the corresponding
formamides were isolated in moderate to high yields (Table 3).
For N-methylaniline (1a), and the product (2a) is isolated in 80%
yield (the NMR yield is 86%). For the N-methylanilines with the
electron-donating -OMe or -Me substituent in para-position, the
isolated yields of the products (2b and 2c) are up to 96% and 87%.
It is interesting that the reaction with the -F substituted substrate
also provides the corresponding product (2d) in 87% yield. When
the N-methylanilines with electron-withdrawing groups such as Cl,
Br and CF3 are used as the substrates, the yields of the products
(2e-2g) decrease to 60%~27%. No formylation occurs when
N-methyl (p-nitroaniline) is used. The isolated yields of the
products are in the order of OMe > Me ≈ F > H > Cl ≈ Br > CF3 >
NO2, which is generally in contrast with the order of their
Hammett constants NO2 (0.78) > CF3 (0.54) > Cl (0.23) ≈ Br (0.23) >
F (0.06) ≈ H (0.00) > Me (-0.17) > OMe (-0.27).[33] The reactions of
N-methylanilines with different substituents in ortho-position
were also investigated. For the -OMe, -Me or -F substituted
substrates, the isolated yields of the products (2i, 2j and 2k) are
87%, 70% and 54%, respectively. N-isopropylaniline can also be
formylated, but the reaction is much slower. The reaction for 48 h
provides the product, N-isopropylformanilide (2l), in 54 % isolated
yield. This formylation also works for the substrate which contains
heteroaryl group. The reaction of 2-(N-methylamino)pyridine
gives N-methyl-N-(2-pyridyl)-formamide (2m) in 69% yield, and
Table 4 Substrate scope for the formylation of secondary aliphatic
amines.a
O
H
2 mol% Zn
H
N
powder
+
+
H2
+
+
2
SiH
(EtO)3
Si]2O
CO2
[(EtO)3
N
R
R'
O
solvent free
R
R'
3
4
O
H
O
H
H
O
H
N
N
N
N
C6H13
C6H13
Me3Si
SiMe3
,
,
,
,
b
n.d.
4a 95
4b 57
4c 44
4d
%
%
%
O
H
O
H
N
O
H
N
N
,
,
,
4e 51
4f 78
4g 47
%
%
%
N
N
H
N
N
H
O
H
O
O
H
O
,
,
,
,
4h 91 %
4i 84 %
4j 76 %
4k 77 %
O
H
N
O
N
O
N
H
N
O
H
O
H
,
,
,
4l 23
4m 53
4n 60
%
%
%
that
of
3-(N-butylamino)thiophene
gives
a Reaction conditions: 3 (5mmol), (EtO)3SiH (12 mmo), 1.5 MPa CO2, Zn
powder (0.1 mmol), 120 oC, 24 h, solvent free, isolated yield. b The NMR
spectrum showed nearly no consumption of hexamethyldisiazane.
N-butyl-N-(3-thiophenyl)-formamide (2n) in 62% isolated yield.
Table 3 Substrate scope for the formylation of N-methyHlaniline derivates.a
O
H
N
N
2 mol% Zn
powder
+
3Si]2O
[(EtO)
+
H2
R'
R'
+
+
CO2
2
SiH
(EtO)3
solvent free
Secondary aliphatic amines can also be formylated with this
protocol (Table 4). The formylation of dihexylamine gives the
product, dihexylamide (4a), in 95% isolated yield. When using
diisopropylamine and dicyclohexylamine as the substrates, the
yields of the products decrease, providing 4b in 57% yield and 4c
in 44% yield, respectively. This indicates that the yields of the
products are sensitive to the steric hindrance of the substrates.
No formylation product is formed when hexamethyldisilazane is
used as the substrate, and nearly no consumption of
hexamethyldisiazane. For the reaction of N-isoprpylmethylamine,
the isolated yield (51%) of the product (4e) is somewhat low, this
is due to a loss during the isolation of the product as the boiling
point of 4e is low. The formylation of N-methylbenzylamine and
dibenzylamine gives the products 4f and 4g in 78% and 47% yields,
respectively. The low yield of 4g once again indicates the steric
effect of the substrate, the steric hindrance decreases the yield of
the product. The reactions of secondary cyclic amines were also
studied. Piperidine, pyrrolidine, 1,2,3,4-tetrahydroquinoline and
indoline can be formylated into the corresponding products 4h-4k
in 76 ~ 91% yields. The reaction of 2,2,6,6-tetramethylpiperidine
gives the product 4l in much low yield (23% yield), due to the
steric congestion of the substrate. Morpholine is formylated into
R
R
1
2
O
H
O
H
O
H
O
H
N
N
N
N
MeO
F
Me
,
,
,
,
2a 80
2b 96
2c 87
2d 87
%
%
%
%
O
H
O
H
O
H
O
H
N
N
N
N
O2N
Cl
F3C
Br
,
,
,
,
b
n.d.
2e 60
2f 59
2g 27
2h
%
%
%
O
N
H
O
H
O
H
O
H
N
N
N
OMe
Me
F
c
,
,
,
,
2l 54%
2i 87
2j 70
2k 54
%
%
%
O
N
H
O
N
H
C4H9
N
S
,
,
2n 62
2m 69
%
%
the
product
4m
in
53%
yield.
When
N,
a Reaction conditions: 1 (5 mmol), (EtO)3SiH (12 mmol), 1.5 MPa CO2, Zn
N'-dimethyl-1,2-ethanediamine is used, the formylation occurs on
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First authoret al.
Report
the both amino groups, providing the product 4n in 60% yield.
Table 5 Urealation of primary amines with CO2 and (EtO)3SiH catalysed by
5). For the primary aromatic amines with the
electron-withdrawing -NO2, -Cl, -Br or -CF3 substituent in
para-position, the isolated yields of the ureas (6b ~ 6e) are from
68% to 86%. The lower isolated yield of the product (6e) (68%) is
due to a loss during the isolation of the product, the NMR
spectrum of the product mixture shows that 6e is formed in ~ 85 %
yield (See the ESI, Fig. S105). For the primary aromatic amines
with the alkyl substituents such -Me, -Bu or -tBu in para-position,
the yields of the products (6f ~ 6h) are from 47% to 58%. When
an electron-donating -OMe group is introduced to the substrate,
the yield of the product 6i becomes low (43%). Therefore,
introducing electron-donating group in the para-position of
primary aromatic amine is not benefit for the urealation reaction,
this is in contrast to that observed in the formylation of N-methyl
aromatic amines, where the electron-donating group in the
para-position promotes the reaction.
Zn powder.a
O
2 mol% Zn
powder
R
R
+
+
2
SiH
(EtO)3
2RNH2
CO2
+
+
2H2
Si]2O
N
H
N
H
[(EtO)3
solvent free
5
6
H
N
H
N
H
N
H
N
H
H
N
N
O
O
O
N
Br
Br
O2
NO2
,
,
,
6a 54 %
6b 86 %
6c 86 %
H
H
N
H
N
H
N
H
N
H
N
N
O
O
O
Cl
Cl
CF3
CF3
Me
Me
,
,
,
6f 58 %
6d 81 %
6e 68 %
H
H
N
H
N
H
N
H
N
H
N
N
The reactions of the primary aromatic amines with different
substituents in ortho-position were also investigated. When using
2-floroaniline, 2-chloroaniline, 2-bromoaniline and 2-iodoaniline
as the substrates, the yields of the ureas (6j-6m) are from 44% to
76%. The reaction of 2-methylaniline provides the product 6n in
77% isolated yield. The ortho-substituent can also be -CF3, in this
case, the urea 6o is obtained in 57% yield. When the
ortho-substituent is -OMe, the yield of urea 6p is low (43%). The
reaction also works for the 2,6-substituted primary aromatic
amines. For the -F, -Cl or -Br substituted ones, the yields of the
products (6q-6s) are from 61% to 82%; for the -Me or -iPr
substituted ones, the yields of the products (6t and 6u) are 93%
and 73%, respectively. 2,4,6-Trimethylaniline is also used as the
O
O
O
nBu
nBu
tBu
Bu
t
MeO
OMe
,
,
,
6i 43 %
6g 47 %
6h 50 %
Cl
Cl
Br
Br
F
F
H
N
H
N
H
N
H
N
H
N
H
N
O
O
O
,
,
,
6l 44 %
6j 69 %
6k 59 %
I
I
CF3
CF3
Me
Me
H
H
N
H
N
H
N
H
N
H
N
N
O
O
O
,
,
,
6m 76 %
6n 77 %
6o 57 %
F
F
Cl
Cl
OMe
OMe
H
N
H
N
H
N
H
N
H
N
H
N
substrate,
the
reaction
provides
O
O
N,N'-di(2,4,6-trimethylphenyl)urea (6v) in 92% yield. The reaction
of 3,5-bis(trifluoromethyl)aniline provides the product 6w in 49%
yield. The primary aliphatic amine, cyclohexylamine, can also
convert in the corresponding urea under the same reaction
conditions, but the yield of the product 6x is low (28%), as this
substrate also undergoes the formylation reaction and produces
42% of N-cyclohexylforamide. On the other hand, when
2-aminopyridine or 3-aminothiophene is the substrate, the
reaction gives a complicated mixture.
O
F
F
Cl
Cl
,
,
,
6p 43 %b
6q 61 %
6r 67 %
iPr
iPr
Br
Br
H
N
H
N
H
N
H
N
H
N
H
N
O
O
O
iPr
Br
Br
iPr
,
,
,
6s 82 %
6t 93 %
6u 73 %
H
H
CF3
N
H
N
N
H
CF3
H
H
N
N
N
O
O
O
CF3
CF3
,
,
,
6v 92 %
6w 49 %
6x 28 %
Table 6 Recycling of Zn powder for the formylation of 1a with CO2 and
(EtO)3SiH.a
H
O
a Reaction conditions: 5 (5 mmol), (EtO)3SiH (12 mmol), 1.5 MPa CO2, Zn
2 mol% Zn
H
N
powder
+
+
2
+
+
CO2
SiH
H2
Si]2O
b
powder (0.1 mmol), 120 oC, 24 h, solvent free, isolated yield. NMR
(EtO)3
[
(EtO)3
N
Ph
solvent free
Ph
yield(we had the difficulty in purifying this product, therefore the yield is
1a
2a
determined by 1H NMR of the mixture).
1H NMR Yields of 2a (%)b
Entry
Interestingly, under the same reaction conditions, when
primary amine, aniline, is used as the substrate, the reaction
provides 1,3-diphenylurea 6a in 54% isolated yield. For the
reaction without zinc powder, no urealation product is observed
under same reaction conditions. If the reaction temperature is
increased to 150 oC, the urealation product is formed in 21% yield
(determined from the NMR spectrum of the reaction mixture).
Twenty-three other primary amines are subsequently tested at
1st
87
91
2nd
83
87
3rd
83
83
4th
5th
88
92
1
2
86
86
a Reaction conditions: 1a (5 mmol), (EtO)3SiH (12 mmol), Zn powder (0.1
mmol). Determined by quantitative 1H NMR using mesitylene as an
b
internal standard.
The recovery and reusability of Zn catalyst were investigated.
After the formylation of N-methylaniline (1a) with CO2 and
(EtO)3SiH, the reaction solution was carefully removed, and the
o
120 C in the presence of 2 mol% Zn powder, and most of them
convert into the urea derivatives in moderate to high yields (Table
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Running title
Chin. J. Chem.
reactants were added for the next run under the same reaction
conditions. This experiment was carried out for twice. As shown
in Table 5, the Zn powder was reused for 5 times in the
formylation reaction without loss of catalytic activity. The
mixtures of reactants and products of the 1st and 5th runs were
collected after the reaction and analysed by the Atomic
Absorption Spectroscopy. The concentrations of zinc in the
mixtures of the 1st and 5th runs are 27 and 1 ppm, respectively.
The zinc concentration in the 1st run is much higher than that in
the 5th run, this is due to the Zn powder used contains a small
amount of soluble Zn salts. After the several runs, these soluble
Zn salts leach out, and therefore the zinc concentration in the 5th
run is very low. The reaction solution of the 1st run was also
analysed by ICP-MS, which indicated the concentrations of other
metals are as the following: Ca, 4.4 ppm; Mg, 0.75 ppm; Na, 1.6
ppm. The catalytic reaction in the presence of MgCl2 or CaI2 but
without Zn powder was investigated. When 2 mol% of MgCl2 was
used, no product was observed; while 2 mol% of CaI2 was used,
no N-methyl-N-phenylformamide was observed and about 5% of
N-methylaniline (1a) was converted into N,N-dimethylamine. We
also added the reactants to the reaction solution containing
soluble zinc species for the catalytic reaction (the zinc powder
was removed by the filtration). Under same reaction conditions,
instead of silylformate, and then the silylcarbamate reacts with
hydrosilane to produce the formamide.
We firstly investigated the reaction of (EtO)3SiH with CO2 (1.5
MPa) at 120 oC in the presence of 2 mol% Zn powder, but without
amine. No silylformate is formed, therefore the pathway 1 can be
excluded. A reaction of 1a with 2.4 equivalents of (EtO)3SiH and
CO2 (1.5 MPa) at 120 oC using 2 mol% of Zn powder as the catalyst
for 24 h gives N-methyl-N-phenylformamide (2a) in 86% yield
(determined by quantitative 1H NMR). But when with 1.0
equivalent of (EtO)3SiH, the reaction gives 2a in 40% yield. The
side product is [(EtO)3Si]2O, and nearly no (EtO)3SiOH is detected.
These results imply that 2a is likely formed through the
silylcarbamate intermediate, which subsequently reacts with one
equivalent of (EtO)3SiH to produce 2a and [(EtO)3Si]2O (pathway
3). Therefore, two equivalents of (EtO)3SiH are necessary for this
N-formylation of amine with CO2. N-formylation in pathway 3 also
explains that the yields of the formylation products decrease
when introducing the electron-withdrawing groups in the
para-position of the N-methylanilines (Table 2). The
electron-withdrawing groups, which make the N-methylanilines
less nucleophilic, are favourable for the reaction in pathway 2 but
not for the reaction in pathway 3.[34b] On the other hand, more
methylation and aminalation products (N,N-dimethylaniline
the
conversion
of
1a
and
the
yield
of
derivatives
+
N,N’-dimethyl-N,N’-diarylmethanediamine
N-methyl-N-phenylformamide (2a) are 14% and 12%, respectively, derivatives) are formed. For examples, for the reactions with 1b,
which are much lower than those in the presence of the zinc
powder.
1a, 1c, 1e, 1f and 1g, the yields of the methylation and
aminalation products are 1.5% + 0, 2.5% + 0, 2.5% + 0, 3% + 6.5%,
6.6% + 8.3%, 14.6% + 0.6%, respectively (determined by
quantitative 1H NMR, see the ESI, Fig. S106-S112). The
experiments on the reactions of formamides (2a, 2f and 2g) with
1.0 equivalent of (EtO)3SiH in the presence of Zn powder at 120 oC
revealed the reactions produce some methylation products but
no aminalation products are formed (see the ESI, Fig. S113-S115).
Therefore, the aminals are formed through the silylformate and
bis(triethoxysiloxy)methane intermediates rather than the
formamides (Scheme 1, pathway 4). This result also indicated that
the reactions generate the silylformate intermediate when the
N-methylanilines with electron-withdrawing groups in
para-position are used as the substrates. Therefore, overall for
the N-methylanilines with hydrogen or electron-donating groups
in para-position, the formylation proceeds in pathway 3; for the
N-methylanilines with electron-withdrawing groups in
para-position, the formylation proceeds in pathway 2 can’t be
excluded as there are silylformate intermediates formed; the
electron-donating groups in the para-position of the
N-methylanilines are benefit for the formylation reaction. During
the catalytic reaction, the surface of zinc powder may activate the
Si-H bond of (EtO)3SiH, therefore being benefit for the reaction of
(EtO)3SiH with carbamate which provides silylcarbamate or
silylformate.
Scheme 1 Pathways for the formylation and aminalation of amines with
CO2 and hydrosilane.
Three possible pathways were suggested for the
N-formylation of amine with CO2 and hydrosilane by other
researchers (Scheme 1).[34] Pathway 1 involves a direct reduction
of CO2 by hydrosilane to give a silylformate, which subsequently
reacts with amine to provide formamide. Pathway 2 is similar to
pathway 1, but the formation of silylformate needs the presence
of amine. CO2 and amine forms carbamate firstly, and then reacts
with hydrosilane to give the silylformate. In the pathway 3, the
carbamate reacts with hydrosilane to afford silylcarbamate
Scheme 2 Suggested pathway for the urealation of primary amines with
CO2 and (EtO)3SiH.
O
O
-
SiOH
RNH2
(EtO)3
RN
C
O
RHN
OSi(OEt)3
RHN
NHR
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First authoret al.
Report
the products. When primary aromatic amines are used as the
substrates, the reactions prefer to produce urea derivatives
instead of formamides. In contrast to that observed in the
formylation reaction, introducing electron-drawing group in the
para-position of primary aromatic amine increases the yields of
the urealation products. The Zn powder can be reused for 5 times
in the formylation reaction without loss of catalytic activity, and
the concentration of zinc in the mixture of reactants and products
We also investigated the pathway for the formation of urea
derivatives. The recent reports showed that the reactions of
silylamines with CO2 provide urea derivatives by Stephan and
co-workers,24 therefore we carried out a reaction of (EtO)3SiH
with N-methylaniline (1a) at 120 oC in the presence of Zn powder.
No silylamine forms, indicating the urealation of amine does not
proceed through a silylamine intermediate. For this catalytic
system, only the primary amines undergo the urealation reactions, of the 5th run is extremely low (~ 1 ppm). For the N-methylanilines
this leads us to suggest that the silylcarbamate intermediates
RN(H)COOSi(OEt)3 lose (EtO)3SiOH to give isocyanates RNCO,
which then react with another primary amine molecule to provide
the urealation products (Scheme 2).[35] The reaction solution of
aniline (5a) and that of para-CF3 substituted aniline (5e) were
analysed by GC-MS, which indicated the formation of the
isocyanates (See the ESI, Fig. S122-S123). When the secondary
amines R2NH are used as the substrates, the reactions generate
the silylcarbamate intermediates R2NCOOSi(OEt)3, which are
unable to lose (EtO)3SiOH to form isocyanates RNCO, therefore
the urealation reactions do not occur. If the urealation reactions
proceed as suggested, when a mixture of primary amine RNH2
and secondary amine R'N(H)Me is used, an unsymmetricurea
derivative RN(H)CON(Me)R' should be formed via the isocyanate
intermediate RNCO. Therefore, we carried out a reaction with the
(p-Br(C6H4)NH2/(C6H5)N(H)Me mixture, and indeed the
unsymmetricurealation product p-Br(C6H4)N(H)CON(Me)C6H5 was
produced in ~ 75 % yield (See the ESI, Fig. S116). The yields of the
urealation products are also in line with this reaction pathway.
The electron-withdrawing groups in the para-position of the
anilines promote the (EtO)3SiOH elimination, when the substrates
with such groups are used, the yields of the products are high
(Table 4, 6b-6d). In the reactions of the anilines containing
electron-donating groups, the yields of the products are low
(Table 4, 6f-6i), and some amounts of formamidines were
observed (See the ESI, Fig. S118), which are formed from the
reactions of the formamides with anilines.[36] The formamides are
generated from the reactions of the silylcarbamates with
hydrosilane, which are competitive with the (EtO)3SiOH
elimination reactions of the silylcarbamates. The reaction of urea
derivative {C6H5N(H)}2CO with one equivalent of (EtO)3SiH in the
presence of 2 mol% Zn powder was also investigated, no
formamidine was observed, indicating the formamidine is not
from the urea.
with hydrogen or electron-donating groups in para-position, the
formylation proceeds through a silylcarbamate intermediate,
while for those with electron-withdrawing groups the formylation
involves the silylformate intermediate can’t be excluded. The
urealation of primary aromatic amines with this catalytic system
likely proceeds through the isocyanate intermediates, and in line
with this mechanism no urealation occurs for the secondary
aromatic amines.
Experimental
General Procedures
All manipulations were performed under air condition.
(EtO)3SiH, Zn powder, mesitylene and CO2 (99.9 %) were used as
received. Solid amines were used without purification, while
liquid amines were dried with CaH2 for 24 h, and then distilled
under vacuum. 1H and 13C NMR spectra were recorded on a
Varian 400 MHz, an Agilent 400 MHz, or a Bruker 400 MHz
spectrometer. All chemical shifts were reported in δ units with
references to the residual solvent resonance of the deuterated
solvents or the SiMe4 internal standard.
Typical procedure for the formylation of secondary amines
with CO2and (EtO)3SiH.
Zn powder (0.1 mmol), secondary amine (5 mmol) and
(EtO)3SiH (12 mmol), mesitylene (1 mmol) and a stir bar were
added to a 100 mL stainless-steel autoclave under air at room
temperature, and then the autoclave was sealed. The atmosphere
of this autoclave was replaced by 0.5 MPa CO2 for three times,
and then the CO2 pressure was increased to 1.5 MPa. The
o
autoclave was sealed and placed in a 120 C oil bath for 24 h,
after that the autoclave was taken out of the oil bath and cooled
to room temperature by water. The CO2 and H2 were released
slowly, and a small drop of the mixture of reactants and products
1
was analysed by H NMR. The remaining mixture was purified by
Conclusions
column chromatography on silica gel (eluent: petroleum
ether/ethyl acetate), and the product was collected.
Zn powder is able to catalyse the formylation and urealation
of amines with CO2 and (EtO)3SiH.
Under the reaction
Typical procedure for the urealation of secondary amines
with CO2and (EtO)3SiH.
conditions of 2.4 equivalents (EtO)3SiH, 1.5 MPa CO2, 2 mol% of
o
Zn powder and 120 C, a series of secondary amines, both the
aromatic ones and the aliphatic ones, can be formylated into
formamides. In the formylation of N-methylanilines with different
substituents in para-position, the electronic effects of
substituents were clearly observed. The isolated yields of the
formylation products are in the order of OMe > Me ≈ F > H > Cl ≈
Br > CF3> NO2, which is generally in contrast with the order of
their Hammett constants. It was also observed that the bulky
substituent on the amine nitrogen atom decreases the yields of
Zn powder (0.1 mmol), primary amine (5 mmol) and (EtO)3SiH
(12 mmol) and a stir bar were added to a 100 mL stainless-steel
autoclave under air at room temperature, and then the autoclave
was sealed. The atmosphere of this autoclave was replaced by 0.5
MPa CO2 for three times, and then the CO2 pressure was
increased to 1.5 MPa. The autoclave was sealed and placed in a
120 oC oil bath for 24 h, after that the autoclave was taken out of
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Chin. J. Chem. 2019,37, XXX－XXX
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Running title
Chin. J. Chem.
the oil bath and cooled to room temperature by water. The CO2
and H2 were were released slowly, and then 30 ml petroleum
ether was added to the mixture of reactants and products under
the stirring. The white precipitates formed were collected by the
filtration, washed with 2 x 10 ml petroleum ether, and dried
under vacuum. Some products were further purified by
recrystallization in acetone or column chromatography on silica
gel.
Huang, Y.; Zhang, J.-P.; Zhang, X.-P.; Zhang, S.-J. Fixation of CO2 into
Cyclic Carbonates Catalyzed by Ionic liquids: a Multi-Scale Approach.
Green Chem. 2015, 17, 108-122. (h) Liu, X. -F.; Li, X. -Y.; Qiao, C.; He, L.
-N.
Transition-Metal-Free
Catalysis
for
the
Reductive
Functionalization of CO2 with Amines. Synlett. 2018, 29, 548-555. (i)
Cao, Y.; He, X.; Wang, N.; Li, R. -H.; He, L. -N. Photochemical and
Electrochemical Carbon Dioxide Utilization with Organic Compounds.
Chin. J. Chem. 2018, 36, 644-659. (j) Xu, P.; Wang, S. -Y.; Fang, Y.; Ji, S.
-J. Research Progress on the Reaction of Carbon Dioxide with
Nucleophiles. Chin. J. Org. Chem. 2018, 38, 1626-1637.
(a) Olah, G. A.; Ohannesian, L.; Arvanaghi, M. Formylating Agents.
Chem. Rev. 1987, 87, 671-686. (b) Weissermel, K.; Arpe H.-J.
Industrial Organic Chemistry, 3rd Edition; Wiley−VCH: Weinheim,
Germany, 1997 (translated by Lindley, C. R.). (c) Peter. G. M. Wuts.
Greene’s Protective Groups in Organic Synthesis, 5th
edition;Wiley−VCH: Weinheim, 2014.
Procedure for reusing of Zn powder in the formylation of
N-methyl-aniline with CO2 and (EtO)3SiH.
Zn powder (0.1 mmol), N-methyl-aniline (5 mmol) and
(EtO)3SiH (12 mmol), mesitylene (1 mmol) and a stir bar were
added to a 100 mL stainless-steel autoclave under air at room
temperature, and then the autoclave was sealed. The atmosphere
of this autoclave was replaced by 0.5 MPa CO2 for three times,
and then the CO2 pressure was increased to 1.5 MPa. The
(a) Motokura, K.; Takahashi, N.; Kashiwame, D.; Yamaguchi, S.; Miyaji,
A.; Baba, T. Copper-Diphosphine Complex Catalysts for
N-Formylation of Amines under 1 Atm of Carbon Dioxide with
Polymethylhydrosiloxane. Catal. Sci. Technol. 2013, 3, 2392-2396. (b)
Santoro, O.; Lazreg, F.; Minenkov, Y.; Cavallo, L.; Cazin, C. S. J.
N-Heterocyclic Carbene Copper(I) Catalysed N-Methylation of
Amines Using CO2. Dalton Trans., 2015, 44, 18138-18144. (c) Zhang,
S.; Mei, Q.-Q.; Liu, H.-Y.; Liu, H.-Z.; Zhang, Z.-P.; Han, B.-X.
Copper-Catalyzed N-Formylation of amines with CO2 under ambient
conditions. RSC Adv., 2016, 6, 32370-32373. (d) Li, R.-P.; Zhao, Y.-F.;
Li, Z.-Y.; Wu, Y.-Y.; Wang, J.-J.; Liu, Z.-M. Choline-based Ionic liquids
for CO2 Capture and Conversion. Sci China Chem. 2019, 62, 256-261.
(a) Molla, R. A.; Bhanja, P.; Ghosh, K.; Islam, S. S.; Bhaumik, A.; Islam,
S. M. Pd Nanoparticles Decorated on Hypercrosslinked Microporous
Polymer: A Highly Efficient Catalyst for the Formylation of Amines
through Carbon Dioxide Fixation. ChemCatChem. 2017, 9, 1939-1946.
(b) Cui, X.-J.; Zhang, Y.; Deng, Y.-Q,; Shi, F. N-Methylation of amine
and nitro compounds with CO2/H2 catalyzed by Pd/CuZrOx under
mild reaction conditions. Chem. Commun. 2014, 50, 13521-13524. (c)
Luo, X.-Y.; Zhang, H.-Y.; Ke, Z.-G.; Wu, C.-L.; Guo, S.-E.; Wu, Y.-Y.; Yu,
B.; Liu, Z.-M. N-doped Carbon Supported Pd Catalysts for
N-Formylation of Amines with CO2/H2. Sci. China Chem. 2018, 61,
725-731.
(a) Kröcher, O.; Köppel, R. A.; Baiker, A. Highly Active Ruthenium
Complexes with Bidentate Phosphine Ligands for the Solvent-free
Catalytic Synthesis of N,N-Dimethylformamide and Methyl Formate.
Chem. Commun. 1997, 453-454. (b) Jessop, P. G.; Hsiao, Y.; Ikariya, T.;
Noyori, R. Catalytic Production of Dimethylformamide from
Supercritical Carbon Dioxide. J. Am. Chem. Soc. 1994, 116, 8851-8852.
(c) Jessop, P. G.; Hsiao, Y.; Ikariya, T.; Noyori, R. Homogeneous
Catalysis in Supercritical Fluids:ꢀ Hydrogenation of Supercritical
Carbon Dioxide to Formic Acid, Alkyl Formates, and Formamides. J.
Am. Chem. Soc. 1996, 118, 344-355. (d) Schmid, L.; Canonica, A.;
Baiker, A. Ruthenium-Catalysed Formylation of Amines with Dense
Carbon Dioxide as C1-Source. Appl.Catal.A. 2003, 255, 23-33. (e)
Munshi, P.; Heldebrant，D. J.; McKoon，E. P.; Kelly，P. A.; Tai，C.-C.
Jessop, P. G. Formanilide and Carbanilide from Aniline and Carbon
Dioxide. Tetrahedron Lett. 2003, 44, 2725-2727. (f) Zhang, L.; Han, Z.;
Zhao, X.; Wang, Z.; Ding, K.-L. Highly Efficient Ruthenium-Catalyzed
N-Formylation of Amines with H2 and CO2 Angew. Chem. Int. Ed.
o
autoclave was sealed and placed in a 120 C oil bath for 24 h,
after that the autoclave was taken out of the oil bath and cooled
to room temperature by water. The CO2 and H2 were released
slowly, and then the solution composed of reactants and products
was removed carefully. The mixture of N-methyl-aniline (5 mmol),
(EtO)3SiH (12 mmol) and mesitylene (1 mmol) was added to the
autoclave for the next run.
Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2018xxxxx.
Acknowledgement
We acknowledge financial support from the National Natural
Science Foundation of China (21732007 and 21821002), the
Strategic Priority Research Program of the Chinese Academy of
Sciences (Grant No. XDB20000000), and Fujian Institute of
Innovation, Chinese Academy of Sciences.
References
Quaranta, E.; Aresta, M. Carbon Dioxide as Chemical Feedstock;
Wiley-VCH: Weinheim, 2010.
(a) Sekine, K.; Yamada, T. Silver-Catalyzed Carboxylation. Chem. Soc.
Rev. 2016, 45, 4524-4532. (b) Banerjee, A.; Dick, G. R.; Yoshino, T.;
Kanan, M. W. Carbon Dioxide Utilization via Carbonate-Promoted
C–H Carboxylation. Nature 2016, 531, 215-219. (c) Wang, M.-Y.;
Wang, N.; Liu, X.-F.; Qiao, C.; He, L.-N. Tungstate Catalysis:
Pressure-switched 2- and 6-electron Reductive Functionalization of
CO2 with Amines and Phenylsilane. Green Chem. 2018, 20, 1564-1570.
(d) Li, Y.; Cui, X.; Dong, K.; Junge, K.; Beller, M. Utilization of CO2 as a
C1 Building Block for Catalytic Methylation Reactions. ACS Catal.
2017, 7, 1077-1086. (e) Yang, Z.-Z.; Yu, B.; Zhang, H.-Y.; Zhao, Y.-F.; Ji,
G.-P.; Ma, Z.-S.; Gao, X.; Liu, Z.-M. B(C6F5)3-Catalyzed Methylation of
Amines Using CO2 as a C1 Building Block. Green Chem. 2015, 17,
4189-4193. (f) Rintjema, J.; Epping, R.; Fiorani, G.; Martin, E.;
Escudero-Adán, E. C.; Kleij, A. W. Substrate-Controlled Product
Divergence: Conversion of CO2 into Heterocyclic Products. Angew.
Chem. Int. Ed. 2016, 55, 3972-3976. (g) Xu, B.-H.; Wang, J.-Q.; Sun, J.;
Chin. J. Chem. 2019,37, XXX－XXX
© 2019SIOC, CAS, Shanghai, & WILEY-VCHVerlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.

First authoret al.
Report
2015, 54, 6186-6189. (g) Zhang, F.-H.; Liu, C.; Li, W.; Tian, G.-L.; Xie,
Chem. Commun. 2016, 52, 2497-2500.
J.-H.; Zhou, Q.-L. An Efficient Ruthenium Catalyst Bearing
Tetradentate Ligand for Hydrogenations of Carbon Dioxide. Chin. J.
Chem. 2018, 36, 1000-1002.
(a) Hao, L.-D.; Zhao, Y.-F.; Yu, B.; Yang, Z.-Z.; Zhang, H.-Y.; Han, B.-X.;
Gao, X.; Liu, Z.-M. Imidazolium-Based Ionic Liquids Catalyzed
Formylation of Amines Using Carbon Dioxide and Phenylsilane at
Room Temperature. ACS Catal. 2015, 5, 4989-4993. (b) Hulla, M.;
Ortiz, D.; Katsyuba, S.; Vasilyev, D.; Dyson, P. J. Delineation of the
Critical Parameters of Salt Catalysts in the N-Formylation of Amines
with CO2. Chem. Eur. J. 2019, 25, 11074-11079. (c) Zhao, W.-F.; Chi,
X.-P.; Li, H.; He, J.; Long, J.-X.; Xu Y.-F.; Yang, S. Eco-Friendly
Acetylcholine-Carboxylate Bio-Ionic liquids for Controllable
N-Methylation and N-Formylation using Ambient CO2 at Low
Temperatures. Green Chem. 2019, 21, 567-577.
(a) Liu, X.-F.; Ma, R.; Qiao, C.; Cao H.; He, L.-N. Fluoride-Catalyzed
Methylation of Amines by Reductive Functionalization of CO2 with
Hydrosilanes. Chem. Eur. J. 2016, 22, 16489-16493. (b) Liu, X.-F.; Li, X.
-Y.; Qiao, C.; Fu, H. -C.; He, L.-N. Betaine Catalysis for Hierarchical
Reduction of CO2 with Amines and Hydrosilane to Form Formamides,
Aminals, and Methylamines. Angew. Chem. Int. Ed. 2017, 56,
7425-7429.
(a) Federsel, C.; Boddien, A.; Jackstell, R.; Jennerjahn, R.; Dyson, P. J.;
Scopelliti, R.; Laurenczy G.; Beller, M. A Well-Defined Iron Catalyst
for the Reduction of Bicarbonates and Carbon Dioxide to Formates,
Alkyl Formates, and Formamides. Angew. Chem. Int. Ed., 2010, 49,
9777-9780. (b) Frogneux, X.; Jacquet O.; Cantat, T. Iron-Catalyzed
Hydrosilylation of CO2: CO2 Conversion to Formamides and
Methylamines. Catal. Sci. Technol. 2014, 4, 1529-1533. (c) Jayarathne,
U.; Hazariand, N.; Bernskoetter, W. H. Selective Iron-Catalyzed
N-Formylation of Amines using Dihydrogen and Carbon Dioxide. ACS
Catal. 2018, 8, 1338-1345.
(a) Daw, P.; Chakraborty, S.; Leitus, G.; Diskin-Posner, Y.; BenDavid, Y.;
Milstein, D. Selective N-Formylation of Amines with H2 and CO2
Catalyzed by Cobalt Pincer Complexes. ACS Catal. 2017, 7, 2500-2504.
(b) Ke, Z.-G.; Yang, Z.-Z.; Liu, Z.-H.; Yu, B.; Zhao, Y.-F.; Guo, S.-E.; Wu,
Y.-Y.; Liu, Z.-M. Cobalt-Catalyzed Synthesis of Unsymmetrically
N,N-Disubstituted Formamides via Reductive Coupling of Primary
Amines and Aldehydes with CO2 and H2. Org. Lett. 2018, 20,
6622-6626.
Lv, H.; Xing, Q.; Yue, C.-T.; Lei Z.-Q.; Li, F.-W. Solvent-promoted
Catalyst-free N-formylation of Amines using Carbon Dioxide under
Ambient Conditions. Chem. Commun. 2016, 52, 6545-6548.
(a) Itagaki, S.; Yamaguchi, K.; Mizuno, N. Catalytic Synthesis of Silyl
Formates with 1 Atm of CO2 and Their Utilization for Synthesis of
Formyl Compounds and Formic Acid. J. Mol. Catal. A: Chem. 2013,
366, 347-352. (b) Nguyen, T. V. Q.; Yoo, W.-J.; Kobayashi, S. Effective
Formylation of Amines with Carbon Dioxide and Diphenylsilane
Catalyzed by Chelating bis(tzNHC) Rhodium Complexes. Angew.
Chem. Int. Ed. 2015, 54, 9209-9212. (c) Lam, R. H.; McQueen, C. M. A.;
Pernik, I.; McBurney, R. T.; Hill, A. F.; Messerle, B. A. Selective
Formylation or Methylation of Amines Using Carbon Dioxide
Catalysed by a Rhodium Perimidine-Based NHC Complex. Green
Chem. 2019, 21, 538-549.
Zhao, T.-X.; Zhai, G.-W.; Liang, J.; Li, P.; Hu X.-B.; Wu, Y.-T.
Catalyst-free N-formylation of Amines using BH3NH3 and CO2 under
Mild Conditions. Chem. Commun. 2017, 53, 8046-8049.
Gomes, C. D. N.; Jacquet, O.; Villiers, C.; Thuéry, P.; Ephritikhine, M.;
Cantat, T. A Diagonal Approach to Chemical Recycling of Carbon
Dioxide: Organocatalytic Transformation for the Reductive
Functionalization of CO2. Angew. Chem. Int. Ed. 2012, 51, 187-190.
(a) Ochoa, J. L.; Porath, J.; Kempf, J.; Egly, J. M. Electron
Donor-Acceptor Properties of Urea and Its Role in Charge-Transfer
Chromatography. J. Chromatogr. A 1980, 188, 257-261. (b) Zhou, Y.;
Zhang, J. F.; Yoon, J. Fluorescence and Colorimetric Chemosensors
for Fluoride-Ion Detection. Chem. Rev. 2014, 114, 5511-5571. (c)
Adams, P.; Baron, F. A. Esters of Carbamic Acid. Chem. Rev. 1965, 65,
567-602. (d) Basch, A.; Zvilichovsky, B.; Hirshman B.; Lewin, M. The
Chemistry of THPC-Urea Polymers and Relationship to Flame
Retardance on Wool and Wool-Polyester Blends. I. Chemistry of
THPC-Urea Polymers. J. Polym. Sci. A 1979, 17, 27-37. (e) Lam, P.;
Jadhav, P.; Eyermann, C.; Hodge, C.; Ru, Y.; Bacheler, L.; Meek, J.;
Otto, M.; Rayner, M.; Wong, Y. Rational Design of Potent,
Bioavailable, Nonpeptide Cyclic Ureas as HIV Protease Inhibitors.
Science. 1994, 263, 380-384. (f) Todorov, T. I.; Yamaguchi, Y.; Morris,
M. D. Effect of Urea on the Polymer Buffer Solutions Used for the
Electrophoretic Separations of Nucleic Acids. Anal. Chem. 2003, 75,
1837-1843. (g) Jayakumar, R.; Nanjundan, S.; Prabaharan, M.
González-Sebastián, L.; Flores-Alamo, M.; García, M. Selective
N-Methylation of Aliphatic Amines with CO2 and Hydrosilanes Using
Nickel-Phosphine Catalysts. Organometallics. 2015, 34, 763-769.
(a) Mitsudome, T.; Urayama, T.; Fujita, S.; Maeno, Z.; Mizugaki, T.;
Jitsukawa, K.; Kaneda, K.
A Titanium Dioxide Supported Gold
Nanoparticle Catalyst for the Selective N ‐ Formylation of
Functionalized Amines with Carbon Dioxide and Hydrogen.
ChemCatChem. 2017, 9, 3632-3636. (b) Tang, G.; Bao, H.-L.; Jin, C.;
Zhong, X.-H.; Du, X.-L.; Direct Methylation of N-Methylaniline with
CO2/H2 Catalyzed by Gold Nanoparticles Supported on Alumina. RSC
Adv. 2015, 5, 99678-99687.
(a) Fang, C.; Lu, C.-L.; Liu, M.-H.; Zhu, Y.-L.; Fu, Y.; Lin, B.-L. Selective
Formylation and Methylation of Amines using Carbon Dioxide and
Hydrosilane Catalyzed by Alkali-Metal Carbonates. ACS Catal. 2016, 6,
7876-7881. (b) Nale D. B.; Bhanage, B. M. An Efficient Protocol for
Formylation of Amines Using Carbon Dioxide and PMHS under
Transition-Metal-Free Conditions. Synlett. 2016, 27, 1413-1417.
(a) Jacquet, O.; Das Neves Gomes, C.; Ephritikhine, M.; Cantat, T.
Recycling of Carbon and Silicon Wastes: Room Temperature
Formylation of N–H Bonds Using Carbon Dioxide and
Polymethylhydrosiloxane. J. Am. Chem. Soc. 2012, 134, 2934-2937.
(b) Das, S.; Bobbink, F. D.; Bulut, S.; Soudani, M.; Dyson, P. J.
Thiazolium Carbene Catalysts for the Fixation of CO2 onto Amines.
Metal-Containing
Polyurethanes,
Poly(urethane–urea)s
and
Poly(urethane–ether)s: A review. React. Funct. Polym. 2006, 66,
299-314.
(a) Nomura, R.; Hasegawa, Y.; Ishimoto, M.; Toyosaki, T.; Matsuda, H.
Carbonylation of Amines by Carbon Dioxide in the Presence of an
Organoantimony Catalyst. J. Org. Chem. 1992, 57, 7339-7342. (b)
Bhanage, B. M.; Fujita, S.; Ikushima, Y.; Arai, M. Synthesis of Cyclic
Ureas and Urethanes from Alkylene Diamines and Amino Alcohols
with Pressurized Carbon Dioxide in the Absence of Catalysts. Green
Chem. 2003, 5, 340-342.
www.cjc.wiley-vch.de
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Running title
Chin. J. Chem.
Ogura, H.; Takeda, K.; Tokue, R.; Kobayashi, T. A Convenient Direct
Synthesis of Ureas from Carbon Dioxide and Amines. Synthesis. 1978,
394-396.
Cooper, C. F.; Falcone, S. J. A Simple One-Pot Procedure for Preparing
Symmetrical Diarylureas from Carbon Dioxide and Aromatic Amines.
Synth. Commun. 1995, 25, 2467-2474.
Yamazaki, N.; Higashi, F.; Iguchi, T. Carbonylation of Amines with
Carbon Dioxide under Atmospheric Conditions. Tetrahedron Lett.
1974, 13, 1191-1194.
(a) Xu, M. T.; Jupp, A. R.; Stephan, D. W. Stoichiometric Reactions of
CO2 and Indium-Silylamides and Catalytic Synthesis of Ureas. Angew.
Chem. Int. Ed. 2017, 56, 14277-14281. (b) Xu, M. T.; Jupp, A. R.; Ong,
M. S. E.; Burton, K. I.; Chitnis, S. S.; Stephan, D. W. Synthesis of Urea
Derivatives from CO2 and Silylamines. Angew. Chem. Int. Ed. 2019,
58, 5707-5711.
CO2 Hydrosilylation. Chem. - Eur. J. 2017, 23, 15908-15912. (e) Feng,
G.-Q.; Du, C.-Y.; Xiang, L.; Rosal, I.D.; Li, G.-Y.; Leng, X.-B.; E. Y. Chen;
Maron L.; Chen, Y.-F. Side Arm Twist on Zn-Catalyzed Hydrosilylative
Reduction of CO2 to Formate and Methanol Equivalents with High
Selectivity and Activity. ACS Catal. 2018, 8, 4710-4718. (f) Tüchler, M.;
Gärtner, L.; Fischer, S.; Boese, A. D.; Belaj, F.; Mösch-Zanetti, N. C.
Efficient CO2 Insertion and Reduction Catalyzed by a Terminal Zinc
Hydride Complex. Angew. Chem. Int. Ed. 2018, 57, 6906 -6909.
Jacquet, O.; Frogneux, X.; Das Neves Gomes, C.; Cantat, T. CO2 as a
C1-Building Block for the Catalytic Methylation of Amines. Chem. Sci.
2013, 4, 2127-2131.
Luo, R.-C.; Lin, X.-W.; Chen, Y.-J.; Zhang, W.-Y.; Zhou, X.-T.; Ji, H.-B.
Cooperative Catalytic Activation of Si-H Bonds: CO2-Based Synthesis
of Formamides from Amines and Hydrosilanes under Mild Conditions.
ChemSusChem. 2017, 10, 1224-1232.
Shi, F.; Zhang, Q.-H.; Ma, Y.-B.; He, Y.; Deng, Y.-Q. From CO Oxidation
to CO2 Activation:ꢀ An Unexpected Catalytic Activity of
Polymer-Supported Nanogold. J. Am. Chem. Soc. 2005, 127,
4182-4183.
Shi, F.; Deng, Y.-Q.; SiMa, T.-L.; Peng, J.-J.; Gu, Y.-L.; Qiao, B.-T.
Alternatives to Phosgene and Carbon Monoxide: Synthesis of
Symmetric Urea Derivatives with Carbon Dioxide in Ionic Liquids.
Angew. Chem. Int. Ed. 2003, 42, 3257-3260.
(a) Ion, A.; Parvulescu, V.; Jacobs, P.; Vos, D. D. Synthesis of
Symmetrical or Asymmetrical Urea Compounds from CO2 via Base
Catalysis. Green Chem. 2007, 9, 158-161. (b) Tamura, M.; Ito, K.;
Nakagawa, Y.; Tomishige, K. CeO2-Catalyzed Direct Synthesis of
Dialkylureas from CO2 and Amines. J. Catal. 2016, 343, 75-85.
Jurado-Vazquez, T.; García, J. J. Iron Catalyzed CO2 Activation with
Organosilanes. Catal. Lett. 2018, 148, 1162-1168.
Hansch, C.; Leo, A.; Taft, R. W. A Survey of Hammett Substituent
Constants and Resonance and Field Parameters. Chem. Rev. 1991, 91,
165-195.
(a) Nicholls, R. L.; McManus, J. A.; Rayner, C. M.; Morales-Serna, J. A.;
White, A. J.; Nguyen, B. N. Guanidine-Catalyzed Reductive Amination
of Carbon Dioxide with Silanes: Switching between Pathways and
Suppressing Catalyst Deactivation. ACS Catal. 2018, 8, 3678-3687. (b)
Hulla, M.; Laurenczy, G.; Dyson, P. J. Mechanistic Study of the
N-Formylation of Amines with Carbon Dioxide and Hydrosilanes. ACS
Catal. 2018, 8, 10619-10630.
(a) Etter, M. C.; Urbanczyk-Lipkowska, Z.; Zia-Ebrahimi, M.; Panunto,
T. W. Hydrogen Bond-Directed Co-crystallization and Molecular
Recognition Properties of Diarylureas. J. Am. Chem. Soc. 1990, 112,
8415-8426. (b) Zhang, Z.; Liao, L.-L.; Yan, S. -C.; Wang, L.; He, Y. -Q.;
Ye, J. -H.; Li, J.; Zhi, Y. -G.; Yu, D. -G. Lactamization of sp2 C-H Bonds
with CO2: Transition-Metal-Free and Redox-Neutral. Angew. Chem.
Int. Ed. 2016, 55, 7068-7072. (c) Wang, S.; Shao, P.; Du, G. -X.; Xi, C. -J.
MeOTf- and TBD-Mediated Carbonylation of ortho-Arylanilines with
CO2 Leading to Phenanthridinones. J. Org. Chem. 2016, 81,
6672−6676.
Enthaler, S.; Wu, X.-F. Zinc Catalysis: Applications in Organic
Synthesis, Wiley-VCH: Weinheim, 2015.
(a) Sattler W.; Parkin, G. Zinc Catalysts for On-Demand Hydrogen
Generation and Carbon Dioxide Functionalization. J. Am. Chem. Soc.
2012, 134, 17462-17465. (b) Rit, A.; Zanardi, A.; Spaniol, T. P.; Maron,
L.; Okuda, J. A Cationic Zinc Hydride Cluster Stabilized by an
N-Heterocyclic Carbene: Synthesis, Reactivity, and Hydrosilylation
Catalysis. Angew. Chem. Int. Ed. 2014, 53, 13273-13277. (c) Specklin,
D.; Fliedel, C.; Gourlaouen, C.; Bruyere, J.-C.; Avilés, T.; Boudon, C.;
Ruhlmann, L.; Dagorne, S. N-Heterocyclic Carbene Based
Tri-organyl-Zn-Alkyl Cations: Synthesis, Structures, and Use in CO2
Functionalization. Chem. -Eur. J. 2017, 23, 5509-5519. (d) Specklin, D.;
Hild, F.; Fliedel, C.; Gourlaouen, C.; Veiros, L. F.; Dagorne, S.
Accessing Two-Coordinate ZnII Organocations by NHC Coordination:
Synthesis, Structure, and Use as π-Lewis Acids in Alkene, Alkyne, and
Mandel, H. G.; Hill, A. J. The Conversion of Formamides into
Formamidines. J. Am. Chem. Soc. 1954, 76, 3978-3982.
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Manuscript revised: XXXX, 2019
Manuscript accepted: XXXX, 2019
Accepted manuscript online: XXXX, 2019
Version of record online: XXXX, 2019
Chin. J. Chem. 2019,37, XXX－XXX
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Zn powder (2mol%) is able to catalyse formylation and urealation of amines with CO2 and
(EtO)3SiH: reactions of secondary amines give formamides while those of primary aromatic amines
provide urea derivatives.
Zinc Powder Catalysed Formylation and
Urealation of Amines using CO2 as C1 Building
Block
Chongyang Du, Yaofeng Chen*
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© 2019SIOC, CAS, Shanghai, & WILEY-VCHVerlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019,37, XXX－XXX
This article is protected by copyright. All rights reserved.