Carboxylation of terminal alkynes with CO2 catalyzed by bis(amidate) rare-earth metal amides

Article abstract of DOI:10.1039/c4gc02200a

Three novel bis(amidate) rare-earth metal amides {LRE[N(SiMe₃)₂]·THF}₂ (H₂L = N,N′-(cyclohexane-1,2-diyl)bis(4-tert-butylbenzamide); RE = La(1), Nd(2), Y(3)), which were prepared by the treatment of the bridged amide proligand H₂L with RE[N(SiMe₃)₂]₃ in tetrahydrofuran, have been characterized by single-crystal X-ray diffraction, elemental analyses, and NMR for complexes 1 and 3. All the complexes were found, for the first time, to be efficient catalysts for the direct carboxylation of terminal alkynes with CO₂ at ambient pressure. And the Nd-based catalyst 2 showed the highest reactivity. Various propiolic acids with a good functional group tolerance were successfully synthesized in high-to-excellent yields under mild conditions. This journal is

Full text of DOI:10.1039/c4gc02200a

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ARTICLE TYPE
Carboxylation of Terminal Alkynes with Carbon Dioxide Catalyzed by
Bridged Bis(amidate) Rare-Earth Metal Amides
†
, †
, †
†
Hao Cheng, Bei Zhao,* Yingming Yao* , Chengrong Lu
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
Three novel bis(amidate) rareꢀearth metal amides {LRE[N(SiMe ) ]⋅THF} (H L= N,N'ꢀ(cyclohexaneꢀ1,2ꢀdiyl)bis(4ꢀtertꢀ
3
2
2
2
butylbenzamide); RE = La(1), Nd(2), Y(3)), which were prepared by the treatment of the bridged amide proligand H L with
2
RE[N(SiMe ) ] in tetrahydrofuran, had been characterized by singleꢀcrystal Xꢀray diffraction, elemental analyses, and NMR for
3
2 3
complexes 1 and 3. All the complexes were found as efficient catalysts for the direct carboxylation of terminal alkynes with CO at
2
1
0
ambient pressure for the first time. And the Ndꢀbased catalyst 2 showed the highest reactivity. Various propiolic acids with good
functional group tolerance were successfully synthesized in high to excellent yields under mild condition.
1
2aꢀb
12c
12d
5
6
6
7
7
5
0
5
0
5
of lactones and lactides,
amidation, and hydroamination.
Introduction
Our group also has interested in the preparation of various
amidate rareꢀearth metal amides for some time and employed
them to several significant catalytic reactions successfully, such
as the ringꢀopening polymerization of racꢀlactide,
addition of terminal alkynes to aromatic nitriles,
Carbon dioxide (CO ), as the primary part of greenhouse gas,
2
1
2
2
3
3
4
4
5
5
0
5
0
5
0
5
0
is a growing problem in climatic change. How to realize emission
reduction and comprehensive utilization are two great challenges
to our mankind. Chemical fixation of carbon dioxide has become
an effective strategy and attracted much attention because of its
1
2e
direct
and
1
2f
1
2g
hydrophosphonylation of aldehydes and unactivated ketones.
intriguing features, such as abundant, inexpensive, nonꢀtoxic and
1
Consideration of the advantages of the bridged ligand, that is, it
can afford a relative rigid and stable framework for the central
metal, easily modify the ligand of its steric and electronic
properties, and restrain the ligand redistribution, we turned to an
unmet challenge item to develop bridged bis(amidate) rareꢀearth
metal complexes. Fortunately, we obtained three novel bridged
bis(amidate) rareꢀearth metal amides {LRE[N(SiMe ) ]⋅THF}
H L = N,N'ꢀ(cyclohexaneꢀ1,2ꢀdiyl) bis(4ꢀtertꢀbutylbenzamide);
RE = La(1), Nd(2), Y(3)) via the treatment of the bridged amide
proligand H L with RE[N(SiMe ) ] . The complexes 1ꢀ3 were
found to be high efficient catalysts for the direct carboxylation by
renewable. Many chemists have applied CO , which is an
2
important C1 carbon feedstock, in synthetic chemistry
1a, 2
successfully.
Since 2010, preparation of alkynyl carboxylic
13
acids and esters, which are important synthons in synthetic and
3
medicinal chemistry, became much more easier than ever
4
before. Atom economic reactions of the direct carboxylation of
terminal alkynes with CO2 in the presence of copperꢀbased
catalysts were independently developed by Gooßen and Zhang
almost at the same time. Soon after, silver(I)ꢀcatalyzed systems
were successively raised by Lu and Gooßen, respectively, and
many functionalized propiolic acids could be obtained in good to
excellent yields. Subsequently, Zhang and his coworkers
successfully grafted silver nanoparticle to an Nꢀheterocyclic
carbene (NHC) polymer to obtain a high activity, excellent
stability and reusability catalyst in the carboxylation of terminal
3 2
2
5
6
(
2
7
8
2
3 2 3
insertion CO into terminal alkynes at ambient pressure. And the
2
Ndꢀbased catalyst 2 showed the highest reactivity. Various
propiolic acids with good functional group tolerance were
successfully synthesized in high to excellent yields under mild
condition.
9
alkynes with carbon dioxide at ambient conditions. Moreover,
mild base cesium carbonate, itself, proved to be efficient singleꢀ
1
0
component catalyst in the transformation. Though all these
methodologies gave us good outcome, harsh terms of relative
Results and Discussion
80
The bridged bis(amidate) rareꢀearth metal amides 1ꢀ3 were
o
10
high temperature (120 C) and relative high pressure (2ꢀ5 atm)
prepared by silylamine elimination reactions of proligand H L,
N,N'ꢀ(cyclohexaneꢀ1,2ꢀdiyl) bis(4ꢀtertꢀbutylbenzamide), with
2
5,7,10
were required in some catalytic systems. The types of
catalysts were still restricted to transition metals of copper and
silver and their complexes. Hence, to improve these deficiencies,
developing new series of catalysts was desirable.
appropriate rareꢀearth metal precursors RE[N(SiMe ) ] in THF at
3
2 3
o
25 C for 24 h. After workup, bridged bis(amidate) rareꢀearth
85 metal amides {LRE[N(SiMe ) ]⋅THF} ·3THF (RE = La (1), Nd
3
2
2
During the past two decades, rareꢀearth metal amides revealed
excellent catalytic activities in organic synthesis because of their
(2), Y (3)) were obtained in good to high yields (Scheme 1). All
the complexes are air and moisture sensitive, and slightly soluble
in THF.
11
unique nature and rich sources. Among these catalyst systems,
1
1aꢀb
the noncyclopentadienyl ancillary ligands, such as amidinate,
11aꢀb
guanidinate,
iminoꢀ or amidoꢀfunctionalized pyrrolyl ligands,
11cꢀe
11fꢀg
and indolyl
were well designed and widely used.
Amidates are another simple N,Oꢀchelating ligands and had
12
attracted some chemists attention in lanthanide chemistry.
Recently, Schafer and Zi independently investigated the synthesis
and applications of amidate rareꢀearth metal complexes, which
showed good to high activities in the ringꢀopening polymerization
90
Scheme 1. Synthesis of bridged bis(amidate) rareꢀearth metal
amides 1ꢀ3.
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The solid state structures of unknown complexes 1-3 were
determined by Xꢀray diffraction analysis of single crystals
smoothly via the same process. Complex 2 was first employed in
the template carboxylation reaction of phenylacetylene (4a) with
obtained from THF solution. They all crystallized in the triclinic 55 CO2 under the atmospheric pressure. As we expected, the
crystal system, Pꢀ1 space group, and have binuclear
centrosymmetric structures. Since complexes 1ꢀ3 are
isomorphous, only the molecular structure of complex 2 is
depicted in Figure 1 as a representation. It shows that complex 2
transformation was successfully accomplished using complex 2
5
0
5
0
5
0
in the presence of Cs CO (Table 1, entry 1). The yields of target
2
3
phenylpropiolic acid (5a) were unsatisfactory while using either
the catalyst precursor 6 Nd[N(TMS) ] (Table 1, entry 2) or just
2
3
is composed of two equivalent subunits, bearing a Nd(III) center 60 complex 2 itself as the catalyst (Table 1, entry 3), or just the
for each moiety. The bridged bis(amidate) group coordinated to
addition of base without rareꢀearth metal catalyst (Table 1, entry
2
o
1
1
2
2
3
each central metal adopts two bonding modes, including
N,O): ꢀO bonding mode and monodentate Oꢀbound. This unique
coordination mode is firstly observed in bridged bis(amidate)
κ
ꢀ
4). When the reaction temperature was raised to 60 C, the
(
ꢀ
increasing yield of phenylpropiolic acid was observed, varying
from 58% to 72% (Table 1, entries 1 and 5). It was found
rareꢀearth metal amides, which is not quite the same as the 65 dimethyl sulfoxide (DMSO) was the optimal solvent in this
14
bonding mode in binaphthylꢀbased amido ytterium complex.
transformation (Table 1, entries 5ꢀ7). To our delight, Laꢀbased
complex 1 and Yꢀbased complex 3 also behaved as active
catalysts in the template reaction under the same condition as for
Each cyclohexaneꢀ1,2ꢀdiyl group takes a most stable chair
conformation and the two CꢀN bonds are located approximately
along the equator of the sixꢀmembered ring. It is the bridged
complex 2 (Table 1, entries 7ꢀ9). Various bases, such as K
CO ,
2 3
2
7
7
8
8
0
5
0
5
Na CO , NaOH, EtONa, diethylamine (DEA), and CsOH were
oxygen atom in the
κ
ꢀ(N,O):
ꢀꢀO bonding amido group
2
3
screened and no desired product was detected, while addition of
triethylamine (TEA) or 1,8ꢀdiazabicyclo[5.4.0]undecꢀ7ꢀene
coordinates to a neodymium atom from the other moiety to
connect two parts of the complex. Thus, the coordination number
of each neodymium is six, that is, three oxygens from two
different bis(amidate) groups, one nitrogen from a bis(amidate)
group, one nitrogen from a silyamido group and one oxygen from
a solvated THF. The geometry around Nd(III) can be described as
a distorted octahedron, with N(3) and O(2) at the two apical
(DBU) led to very low yields of phenylpropiolic acid (Table 1,
entries 10ꢀ17). It shows Cs CO3 is the ideal additive in the
2
carboxylation reaction, which is consistent with the result in
1
0
published work.
Presumably the relative high temperature
6
o
could led to the unexpected decarboxylation process, 40 C is
proved to be the optimal temperature (Table 1, entries 18ꢀ20). The
dosage of catalyst, additive cesium carbonate and solvent DMSO,
and reaction time play important roles in the carboxylation
o
positions (O(2)ꢀNd(1)ꢀN(3) 132.68(17) ), and O(1), O(3), O(2A),
and N(2) approximately coplanar with the neodymium atom (the
o
sum of the central angles is 350.8 ).
reaction of phenylacetylene with CO as well. After carefully
The bond parameters in complexes 1 and 3 are similar to the
corresponding values in complex 2, thinking about the differences
in ionic radii.
2
investigation, this transformation produced the desired
phenylpropiolic acid up to 94% yield using 4 mol% catalyst 2 in
the presence of 2 equiv. Cs CO in 5 mL DMSO for 24 hours
2
3
under constant pressure (See SI, Table 3).
Table 1 Screening of the optimal conditions of the carboxylation
a
of phenylacetylene with CO2.
o
b
Entry
1
2
3
4
5
6
7
8
Cat.
2
6
2
ꢀ
Base
Solvent T/ C Yield/%
Cs CO3
DMF
DMF
DMF
25
25
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
40
50
80
58
13
trace
8
2
Cs CO3
2
ꢀ
Figure 1. Structure of bridged bis(amidate) neodymium amide
Cs CO3
DMF
2
2⋅3THF. Hydrogen atoms and the molecule of THF in the unit
2
2
2
1
3
2
2
2
2
2
2
2
2
2
2
2
Cs
2
Cs
2
Cs
2
Cs
2
Cs
2
CO
CO
CO
CO
CO
3
3
3
3
3
DMF
Tol
72
20
89
80
80
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
15
40
ꢀ
90
86
87
3
5
cell are omitted for clarity. Selected bond lengths (Å) and bond
angles (deg): Nd(1)ꢀN(3) 2.346(5), Nd(1)ꢀO(1) 2.223(4), Nd(1)ꢀ
N(2) 2.526(5), Nd(1)ꢀO(2) 2.593(4), Nd(1)ꢀO(2A) 2.395(4),
O(1)ꢀC(1) 1.323(8), N(1)ꢀC(1) 1.289(8), O(2)ꢀC(18) 1.322(7),
N(2)ꢀC(18) 1.295(7); O(1)ꢀNd(1)ꢀO(3) 79.46(17), O(3)ꢀNd(1)ꢀ
O(2A) 77.63(17), O(2A)ꢀNd(1)ꢀN(2) 116.76(15), N(2)ꢀNd(1)ꢀO(1)
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
9
10
11
12
K
Na
CO
CO
2
3
40
2
3
7
6.92(17), N(3)ꢀNd(1)ꢀO(2) 132.68(17).
NaOH
EtONa
DEA
TEA
DBU
1
1
1
1
1
1
1
2
3
4
5
6
7
8
9
0
Carboxylation of Terminal Alkynes with Carbon
Dioxide Catalyzed by Bridged Bis(Amidate) Rare-
Earth Metal Amides.
45
CsOH
6
7
Based on the mechanism raised by Zhang, Lu, and
Cs CO3
2
8
Gooßen, metal acetylide is one of the key intermediates in the
Cs CO3
2
carboxylation of terminal alkyne with carbon dioxide catalyzed
by metalꢀbased catalyst. Since we predicted that treatment of rare
earth metal amide with alkyne produce rareꢀearth metal acetylide,
Cs CO3
2
a
90
Reaction condition: phenylacetylene (1.0 mmol), base (3.0
50
b
mmol), catalyst (0.04 mmol), CO (balloon), solvent (10 mL).
Isolated yields.
1
2f
2
we believe that the novel bis(amidate) rareꢀearth metal amides
1
ꢀ3 can catalyze the carboxylation of terminal alkyne with CO2
2
| Journal Name, [year], [vol], 00–00
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With respect to terminal alkynes, the tolerance of substituent
groups was explored under the optimized reaction conditions.
Various substituted terminal alkynes were examined, and the
results are listed in Table 2. The electronic effect of substituent
groups on the phenyl ring affects the reactions greatly. Excellent
yields, varied from 90ꢀ99%, are achieved when the substrates are
bearing electron withdrawing groups (EWG), both weak EWG
halides (Table 2, 5b-f) and very strong EWG nitro group and
trifluoromethyl group (Table 2, 5g-i). The high yields of 80ꢀ86%
are obtained when the substrates bearing electron donating groups,
such as methyl group, tertꢀbutyl group, and phenyl group (Table 2,
Catalyzed by Bridged Bis(amidate) Rare-Earth
Metal Amides.
To gain some insights into the mechanism of the carboxylation
reaction, a stoichiometric reaction of Yꢀbased catalyst 3 with
3
4
4
5
5
0
5
0
5
phenylacetylene was carried out in d ꢀTHF in a NMR tube. The
8
ꢀ
change of chemical shifts of (SiMe ) N groups during reaction is
3
2
illustrated in Figure 2. Signals assignable to coordinating
ꢀ
(SiMe ) N groups in catalyst 3 are observed at 0.20 and 0.04
3
2
ppm, respectively (a). 30 min after the addition of
phenylacetylene, the integration of the downfield signal
significantly decreased, while a new resonance appeared at 0.05
ppm which overlaps with the original signal at 0.04 ppm (b).
After 6 h reaction, the signal at 0.20 ppm completely disappeared.
Only the new signal at 0.05 ppm remained with the integration of
1
1
2
2
0
5
0
5
5
j-m). However, the yield dramatically drops to 70% when the
substituent is a methoxy group, which may be attributes to the
poison of the catalyst by the methoxy group (Table 2, 5n). The
high efficient catalyst system also performed excellent in the case
of hetero aromatic rings and fused aromatic ring (Table 2, entries
3
6H, which can be assigned to the methyl groups of HN(SiMe3)2
that results from the aminolysis of amide with phenylacetylene
c). The identity of HN(SiMe ) was further confirmed by adding
5
o-q). Dialkynes, for example 1,3ꢀ and 1,4ꢀdiethynylbenzene also
(
3
2
give us the corresponding dicarboxylic acids in satisfactory yields
with the loading of the starting materials are reduced by half
(Table 2, 5r-s). Unfortunately, the bridged bis(amidate) rareꢀearth
metal amides are found to be unreactive towards aliphatic alkynes,
e.g. ethynyltrimethylsilane and 1ꢀhexyne, and could not afford the
desired products under the current reaction conditions.
additional HN(SiMe ) into the NMR tube.
3
2
Table 2. Substrate scope for the catalytic carboxylation of
a, b
terminal alkynes with CO2.
1
Figure 2. H NMR monitoring of the stoichiometric reaction
between Yꢀbased catalyst 3 and phenylacetylene. (a) the spectrum
of catalyst 3; (b) 30 min after the addition of phenylacetylene; (c)
5
6
6
5
0
5
6
h after the addition of phenylacetylene.
6ꢀ8
Based on this finding and some literature reports, we proposed
a possible mechanism for our catalytic system in Scheme 2. The
metal acetylide intermediate A was speculated to form after the
aminolysis of the bridged bis(amidate) rareꢀearth metal amides.
Subsequently, carbon dioxide coordinated and inserted into the
LnꢀC bond of intermediate A to generate the rareꢀearth metal
carboxylate B. In the presence of a large amount of cesium
carbonate and alkyne substrates, the transmetallation occurred
rapidly, and the formation of cesium carboxylate C and
regeneration of A was instantly completed. After the mixture was
quenched by acidic aqueous, the desired product D was achieved.
a
Reaction condition: alkyne (1.0 mmol), Cs CO (2.0 mmol),
2
3
b
catalyst 2 (0.04 mmol), CO (balloon), DMSO (5 mL). Isolated
yields. alkyne (0.5 mmol).
2
c
3
0
70
Scheme 2. A possible mechanism for the carboxylation catalyzed
A Possible Mechanism of the Carboxylation
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2
by bridged bis(amidate) rareꢀearth metal amides.
65 F . All the nonꢀhydrogen atoms were refined anisotropically.
Hydrogen atoms were all generated geometrically with assigned
appropriate isotropic thermal parameters.
Experimental
All manipulations and reactions were conducted under purified
argon or CO atmosphere by using standard Schlenk techniques.
2
5
0
5
0
5
0
Rareꢀearth metal amides RE[N(SiMe ) ] (RE = La, Nd, Y), and
3
2 3
General procedure for the synthesis of propiolic acids from
proligand
H2L
(N,N'ꢀ(cyclohexaneꢀ1,2ꢀdiyl)ꢀbis(4ꢀtertꢀ
7
7
8
8
0
5
0
5
reactions of terminal alkynes with CO by complex 2
2
15
butylbenzamide) were prepared according to literature methods.
A 15 mL Schlenk flask, equipped with a magnetic stirring bar,
was charged with the complex 2 (61.8 mg, 0.04 mmol) and
Cs CO (621 mg, 1.91 mmol). Alkyne (1.0 mmol) and anhydrous
Solvents were distilled from sodium benzophenone ketyl under
argon prior to use unless otherwise noted. Solid alkynes were
degassed before use, and liquid alkynes were distilled from
molecular sieve prior to use. The single crystal Xꢀray diffraction
2
3
1
1
2
2
3
DMSO (5 mL) were added with syringe in turn, shortly after
purging the Schlenk flask with CO2 three times. Whereafter,
carbon dioxide was introduced with a balloon at ambient pressure.
data were recorded on
diffractometer. H, C and F NMR spectra were obtained on a
a Rigaku Mercury CCD Xꢀray
1
13
19
o
The reaction mixture was stirred at 40 C for 24 h, then cooled
Unity Inovaꢀ400 spectrometer in DMSOꢀd or CDCl . Carbon,
6
3
down to room temperature. The reaction mixture was filtrated
followed by quenched with water (15 mL), then acidified with
aqueous HCl (6 N, 20 mL), and extracted with diethyl ether (4 ×
hydrogen, and nitrogen analyses were performed by direct
combustion on a CarloꢀErba EAꢀ1110 instrument. Metal analyses
were carried out by complexometric titration. Melting points
were determined in sealed Arꢀfilled capillary tubes and are
uncorrected.
1
0 mL). The combined organic layers were washed with brine,
dried over anhydrous Na SO4 and filtered. The solvent was
2
removed under vacuum to afford the target acid product. Data for
1
13
H and C NMR of acids were all conducted in CDCl3 or
General
{
procedure
LRE[N(SiMe ) ]⋅THF}
2
for
the
synthesis
of
DMSOꢀd , and consistent with the data in reported literatures.
6
3
2
To a stirred THF solution of RE[N(SiMe ) ] (1.49 mmol, 10
1
3
2 3
Phenylpropiolic acid (5a). H NMR (400 MHz, CDCl )：δ 7.62
3
mL
of
THF),
N,N'ꢀ(cyclohexaneꢀ1,2ꢀdiyl)ꢀbis(4ꢀtertꢀ
(
m, J = 8.4 Hz, 2H, ArH); 7.49 (m, J = 7.5 Hz, 1H, ArH); 7.40 (m,
butylbenzamide) (0.65 g, 1.49 mmol) in 10 mL THF was slowly
13
J = 7.5 Hz, 2H, ArH) ppm. C NMR (100 MHz, CDCl ): δ 158.1,
o
3
added. After the mixture was stirred at 25 C for 24 h, the solvent
9
0
133.4, 131.2, 128.8, 119.3, 88.8, 80.3 ppm. HRMS (ESI, m/z)
was pumped off, and the residue was recrystallized from THF at
room temperature to give pure crystals. Characterized data for
complexes 1ꢀ3 were collected as follows.
+
calcd. for C H O H : 147.0440, found: 147.0452.
9
6
2
1
2
ꢀFluorophenylpropiolic acid (5b). H NMR (400 MHz, DMSOꢀ
d )：δ 7.71 (td, J = 7.5, J = 1.7 Hz, 1H, ArH); 7.64ꢀ7.56 (m, 1H,
6
1
2
{
LLa[N(SiMe ) ]⋅THF} (1): colorless crystals. Yield: 1.02 g
3 2 2
o
9
5
ArH); 7.40 (t, J = 9.1 Hz, 1H, ArH); 7.32 (t, J = 7.6 Hz, 1H, ArH)
(85%). Mp. 294.5ꢀ296.4 C. Anal. Calcd for C H N O La Si
13
1
7
6
126
6
6
2
4
ppm. C NMR (100 MHz, DMSOꢀd ): δ 162.9 ( J = 251.0 Hz),
6
CꢀF
(
8
1606.69): C 56.70, H 7.89, N 5.22, La 17.26; Found: C 56.98, H
3
4
1
(
54.1, 134.6, 133.5 ( J = 8.0 Hz), 125.2 ( J = 3.0 Hz), 116.1
JCꢀF = 13.0 Hz), 107.6 ( J
Hz) ,77.7 ppm. F NMR (376.5 MHz, DMSOꢀd ): δ ꢀ109.0 ppm.
00 HRMS (ESI, m/z) calcd. For C H O F Na : 187.0165, found:
1
CꢀF CꢀF
.02, N 5.23, La 17.30. H NMR (THFꢀd , 400 MHz): δ 7.94 (d, J
2
2
3
8
= 15.0 Hz), 86.3 ( J
= 3.0
CꢀF
CꢀF
35
40
45
= 8.5 Hz, 1H, ArH); 7.77 (d, J = 8.3 Hz, 1H, ArH); 7.62 (d, J =
19
6
8
1
1
3
.4 Hz, 3H, ArH); 7.55ꢀ7.52 (m, 4H, ArH); 7.38 (d, J = 8.5 Hz,
H, ArH); 7.30 – 7.22 (m, 6H, ArH); 3.68 – 3.63 (m, 8H); 1.84 –
.79 (m, 8H); 1.53 – 1.18 (m, 56H); 0.27 (s, 6H); 0.08ꢀ0.05 (m,
0H) ppm.
+
1
1
1
1
9 5 2
1
87.0167.
1
4
ꢀFluorophenylpropiolic acid (5c). H NMR (400 MHz, CDCl ):
3
13
δ 7.65ꢀ7.60 (m, 2H, ArH); 7.13ꢀ7.07 (m, 2H, ArH) ppm.
05 NMR (100 MHz, CDCl ): δ 164.4 ( J = 253.0 Hz), 158.2,
35.8 ( J = 9.0 Hz), 116.5 ( J = 13.0 Hz), 115.3 ( J = 3.0
CꢀF CꢀF CꢀF
Hz), 88.1, 80.1 ppm. F NMR (376.5 MHz, CDCl ): δ ꢀ105.4
C
{
LNd[N(SiMe ) ]⋅THF} (2): blue crystals. Yield: 1.06 g (88%).
1
3
2
2
o
3
CꢀF
Mp. 293.8ꢀ295.3 C. Anal. Calcd for C H N O Nd Si
3
2
4
7
6
126
6
6
2
4
1
(1614.69): C 56.32, H 7.84, N 5.19, Nd 17.80; Found: C 56.40, H
19
3
7
.98, N 5.23, Nd 17.85.
+
ppm. HRMS (ESI, m/z) calcd. For C H O F H : 165.0346, found:
9
5
2
1
65.0347.
{
LY[N(SiMe ) ]⋅THF} (3): colorless crystals. Yield: 0.75g
3 2 2
o
10
(67%). Mp. 294.2ꢀ296.1 C. Anal. Calcd for C H N O Y Si
1
7
6
126
6
6
2
4
4
ꢀChlorophenylpropiolic acid (5d). H NMR (400 MHz, DMSOꢀ
(
8
1506.69): C 60.45, H 8.41, N 5.57, Y 11.78; Found: C 60.52, H
d ): δ 7.66 (d, J = 8.2 Hz, 2H, ArH); 7.55 (d, J = 8.4 Hz, 2H, ArH)
6
1
.48, N 5.61, Y 11.90. H NMR (THFꢀd , 400 MHz): δ 7.84 (d, J
13
8
ppm. C NMR (100 MHz, DMSOꢀd ): δ 154.1, 135.8, 134.4,
6
50
55
60
= 8.4 Hz, 3H, ArH); 7.55 – 7.49 (m, 3H, ArH); 7.39 (s, 6H, ArH);
1
29.3, 117.8, 83.1, 82.5 ppm. HRMS (ESI, m/z) calcd. For
7
8
.30 – 7.23 (m, 4H, ArH); 3.63 – 3.58 (m, 8H); 1.82 – 1.75 (m,
H); 1.37– 1.31 (m, 56H); 0.20 (s, 18H); 0.04 (s, 18H) ppm.
+
15 C H O Cl Na : 202.9870, found: 202.9876.
9
5
2
1
4
ꢀBromophenylpropiolic acid (5e). H NMR (400 MHz, DMSOꢀ
X-ray structure determination of complexes 1-3
d )：δ 7.69 (d, J = 8.2 Hz, 2H, ArH); 7.58 (d, J = 7.8 Hz, 2H,
6
Owing to their air and moisture sensitivity, suitable single
crystals of complexes 1ꢀ3 were each sealed in thinꢀwalled glass
capillaries. Intensity data were collected on a Rigaku Mercury
CCD equipped with graphiteꢀmonochromatized Mo Kα (λ =
13
ArH) ppm. C NMR (100 MHz, DMSOꢀd ): δ 154.1, 134.4,
6
1
20 132.1, 124.7, 118.2, 83.2, 82.6 ppm. HRMS (ESI, m/z) calcd. For
+
C H O Br Na : 246.9365, found: 246.9365.
9
5
2
0
.71075 Å) radiation for complexes 1-3. Details of the intensity
1
3
ꢀBromophenylpropiolic acid (5f). H NMR (400 MHz, DMSOꢀ
data collection and crystal data are given in Tables 1 and 2 in SI.
The crystal structures of these complexes were solved by direct
methods, expanded by Fourier techniques and refined by using
d6): δ 7.85 (t, J = 1.6 Hz, 1H, ArH); 7.75 (d, J = 8.1 Hz, 1H, ArH);
1
25 7.64 (d, J = 7.8 Hz, 1H, ArH); 7.42 (t, J = 7.9 Hz, 1H, ArH) ppm.
13
C NMR (100 MHz, DMSOꢀd ): δ 154.0, 134.6, 133.9, 131.6,
1
6
6
the SHELXLꢀ97 program. Atomic coordinates and thermal
parameters were refined by full matrix leastꢀsquares analysis on
1
31.1, 121.9, 121.2, 82.6, 82.4 ppm. HRMS (ESI, m/z) calcd. For
+
C H O Br Na : 246.9365, found: 246.9370.
9
5
2
4
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 5 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C4GC02200A
1
4
ꢀNitrophenylpropiolic acid (5g). H NMR (400 MHz, DMSOꢀ 65 129.9, 127.8, 117.9, 81.5, 80.3 ppm. HRMS (ESI, m/z) calcd. For
+
d ): δ 8.29 (d, J = 8.8 Hz, 2H, ArH); 7.91 (d, J = 8.8 Hz, 2H, ArH)
ppm. C NMR (100 MHz, DMSOꢀd ): δ 153.8, 148.2, 133.8,
25.6, 124.0, 85.0, 81.7 ppm. HRMS (ESI, m/z) calcd. For
C H O N Na : 214.0110, found: 214.0115.
C H O S H : 153.0005, found: 153.0010.
6
7 4 2
13
6
1
1
3ꢀ(pyrenꢀ1ꢀyl)propiolic acid (5q). H NMR (400 MHz, DMSOꢀ
+
5
9 5 4
d )：δ 8.53 – 8.37 (m, 4H, ArH); 8.37 – 8.28 (m, 3H, ArH); 8.24
6
1
3
70
(d, J = 8.9 Hz, 1H, ArH); 8.16 (t, J = 7.7 Hz, 1H) ppm. C NMR
1
4
ꢀTrifluoromethylphenylpropiolic acid (5h). H NMR (400 MHz,
DMSOꢀd ): δ 7.92 – 7.76 (m, 4H, ArH) ppm. C NMR (100
MHz, DMSOꢀd ): δ 154.4, 133.8, 130.8 ( J = 30.0 Hz), 126.3
(100 MHz, DMSOꢀd ): δ 154.9, 131.3, 131.0, 130.7, 130.2, 130.0,
6
1
3
6
127.6, 127.4, 127.1, 125.4, 123.4, 113.2, 87.6, 83.9 ppm. HRMS
2
+
6
CꢀF
(ESI, m/z) calcd. For C H O H : 271.0753, found: 271.0768.
19 10
2
3
1
1
1
2
0
5
0
( J = 4.0 Hz), 125.5, 124.1( J = 271.0 Hz), 83.9, 82.7 ppm.
CꢀF CꢀF
19
1
F NMR (376.5 MHz, DMSOꢀd ): δ ꢀ61.6 ppm. HRMS (ESI, m/z) 75 3,3'ꢀ(1,3ꢀphenylene)dipropiolic acid (5r). H NMR (400 MHz,
calcd. For C H O F H : 215.0314, found: 215.03116.
6
+
1
0
5
2
3
DMSOꢀd ): δ7.86 (s, 1H, ArH); 7.78 (dd, J = 7.8, 1.5 Hz, 2H,
ArH); 7.57 (t, J = 7.8 Hz, 1H) ppm. C NMR (100 MHz,
6
13
1
3
ꢀ(3,5ꢀbis(trifluoromethyl)phenyl)propiolic acid(5i). H NMR
(400 MHz, DMSOꢀd ): δ 8.38 (s, 2H, ArH); 8.28 (s, 1H, ArH)
ppm. C NMR (100 MHz, DMSOꢀd ): δ 154.2, 133.6 ( J = 4.0 80 237.0150.
Hz), 131.5 ( J = 33.4 Hz), 124.5, 123.2 ( J = 272.0 Hz),
22.4, 84.4, 81.0 ppm. F NMR (376.5 MHz, DMSOꢀd ): δ ꢀ61.6
ppm. HRMS (ESI, m/z) calcd. For C H O F H : 283.0188,
DMSOꢀd ): δ 154.5, 136.3, 135.1, 130.3, 120.4, 83.0, 82.9 ppm.
6
+
6
HRMS (ESI, m/z) calcd. For C H O Na : 237.0158, found:
12
6
4
13
3
6
CꢀF
2
1
CꢀF
CꢀF
1
9
1
1
3,3'ꢀ(1,4ꢀphenylene)dipropiolic acid (5s). H NMR (400 MHz,
6
+
13
11
4
2
6
DMSOꢀd ): δ 7.71 (s, 4H, ArH) ppm. C NMR (100 MHz,
6
found: 283.0191.
DMSOꢀd ): δ 154.1, 133.0, 121.2, 83.8, 83.0 ppm. HRMS (ESI,
6
+
85
m/z) calcd. For C H O Na : 237.0158, found: 237.0151.
12
6
4
1
4
ꢀMethylphenylpropiolic acid (5j).
H NMR (400 MHz,
CDCl )：δ 7.51 (d, J = 8.1 Hz, 2H, ArH); 7.20 (d, J = 8.0 Hz, 2H,
Conclusion
3
1
3
ArH); 2.39(s, 3H, CH ) ppm. C NMR (100 MHz, CDCl ): δ
In summary, three novel bridged bisamidate rare earth metal
3
3
2
5
158.4, 142.0, 133.4, 129.6, 116.1, 89.7, 79.9, 21.9 ppm. HRMS
amides {LRE[N(SiMe ) ]⋅THF} (RE = La (1), Nd (2), Y(3); H L
= N,N'ꢀ(cyclohexaneꢀ1,2ꢀdiyl)bis(4ꢀtertꢀbutylbenzamide)) had
3
2
2
2
+
(
ESI, m/z) calcd. For C H O H : 161.0597, found: 161.0596.
10 8 2
90
been prepared through the reactions of the bridged amide
proligand H L with RE[N(SiMe ) ] in good yields. Xꢀray
1
3
ꢀMethylphenylpropiolic acid (5k).
H NMR (400 MHz,
2
3 2 3
CDCl )：δ 7.46 – 7.39 (m, 2H, ArH); 7.29 (m, J = 5.7, 0.8 Hz,
structural analysis shows that compounds 1-3 are binuclear
centrosymmetric structures. It is the first time that the bridged
3
1
3
3
3
4
4
5
5
0
5
0
5
0
5
2H, ArH); 2.36 (s, 3H, CH ) ppm. C NMR (100 MHz, CDCl3):
3
δ 158.4, 138.6, 133.9, 132.2, 128.7, 119.0, 89.5, 21.3 ppm. 95 bisamidate rare earth metal amides were successfully employed
+
HRMS (ESI, m/z) calcd. For C H O Na : 183.0416, found:
in the valuable carboxylation of terminal alkynes with CO in the
2
1
0
8
2
1
83.0422.
presence of cesium carbonate under constant pressure. Especially,
complex 2 with central metal Nd performed the highest activity
among those amides and gave us high to excellent yields for
1
4ꢀtertꢀButylphenylpropiolic acid (5l). H NMR (400 MHz,
CDCl ): δ 7.56 (d, J = 8.5 Hz, 2H, ArH); 7.42 (d, J = 8.5 Hz, 2H, 100 aromatic substrates with good tolerance of substituents. It is a
3
1
3
ArH); 1.32(s, 9H, CH ) ppm. C NMR (100 MHz, CDCl ): δ
convenient access to important propiolic acid and its derivatives.
Many efforts to make clear of the catalytic mechanism and to
explore of new efficient catalysts were still in process in our lab.
3
3
1
58.5, 155.0, 133.3, 125.9, 116.1, 89.7, 79.9, 35.2, 31.1 ppm.
+
HRMS (ESI, m/z) calcd. For C H O Na : 225.0886, found:
1
3
14
2
225.0887.
Notes
1
3
ꢀ(biphenylꢀ4ꢀyl)propiolic acid (5m). H NMR (400 MHz,
a
1
05
Key Laboratory of Organic Synthesis of Jiangsu Province,
DMSOꢀd ): δ 7.90 – 7.62 (m, 6H, ArH); 7.50 (t, J = 7.5 Hz, 2H,
ArH); 7.42 (t, J = 7.3 Hz, 1H, ArH) ppm. C NMR (100 MHz,
DMSOꢀd ): δ 154.3, 142.3, 138.7, 133.3, 129.1, 128.3, 127.2,
26.8, 117.8, 84.4, 82.4 ppm. HRMS (ESI, m/z) calcd. For
6
1
3
College of Chemistry, Chemical Engineering and Materials
Science, Dushu Lake Campus, Soochow University, Suzhou
6
2
15123, People’s Republic of China. Fax: +86ꢀ512ꢀ65880305;
1
+
Tel: +86ꢀ512ꢀ65880305; Eꢀmail: zhaobei@suda.edu.cn
10 † Electronic Supplementary Information (ESI) available: General
procedures for preparations of complexes and substrates and
catalysis, characterization data, H and C NMR spectra,
crystallographic data for complexes 1ꢀ3 [CCDC: 1017174 (1),
C H O Na : 245.0573, found: 245.0569.
1
5
10
2
1
1
1
4
ꢀMethoxylphenylpropiolic acid (5n). H NMR (400 MHz,
1
13
CDCl ): δ 7.57 (d, J = 8.9 Hz, 2H, ArH); 6.90 (d, J = 8.9 Hz, 2H,
ArH); δ 3.85 (s, 3H, CH ) ppm. C NMR (100 MHz, CDCl ): δ
62.0, 158.3, 135.4, 114.5, 111.0, 90.0, 79.8, 55.6 ppm. HRMS
ESI, m/z) calcd. For C H O H : 177.0546, found: 177.0559.
3
1
3
3
3
1
017173 (2), 1017176 (3)] and figures depicting solid state
1
(
15 structures. See DOI: 10.1039/b000000x/
+
10 8 3
1
Acknowledgment
3ꢀ(thiophenꢀ2ꢀyl)propiolic acid (5o). H NMR (400 MHz,
CDCl )：δ 7.55 (dd, J = 3.7 Hz, J = 1.1 Hz, 1H, ArH); 7.52 (dd,
3
1
2
We gratefully acknowledge financial supports from the National
Natural Science Foundation of China (Grant Nos. 21172165,
21132002 and 21372172), PAPD, the Major Research Project of
J = 5.1 Hz, J = 1.1 Hz, 1H, ArH); 7.08 (dd, J = 5.1 Hz, J = 3.8
Hz, 1H, ArH) ppm. C NMR (100 MHz, CDCl ): δ 158.2, 137.5,
1
2
1
2
1
3
3
1
32.2, 127.8, 119.0, 84.6, 83.3 ppm. HRMS (ESI, m/z) calcd. For 120 the Natural Science Foundation of the Jiangsu Higher Education
+
6
0
C H O S H : 153.0005, found: 153.0010.
Institutions (Project 14KJA150007), and the Qing Lan Project.
7
4
2
1
3
ꢀ(thiophenꢀ3ꢀyl)propiolic acid (5p). H NMR (400 MHz,
References
DMSOꢀd )：δ 8.19 (s, 1H, ArH); 7.70 (s, 1H, ArH); 7.33 (s, 1H,
6
13
1 (a) T. Sakakura, J. C. Choi and H. Yasuda, Chem. Rev., 2007, 107,
ArH) ppm. C NMR (100 MHz, DMSOꢀd ): δ 154.4, 134.9,
6
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 5

Green Chemistry
Page 6 of 7
View Article Online
DOI: 10.1039/C4GC02200A
2
1
4
3
365–2387; (b) T. Sakakura and K. Kohnoa, Chem. Commun., 2009, 11,
312–1330; (c) A. Correa and R. Martín, Angew. Chem. Int. Ed., 2009, 75 8 M. Arndt, E. Risto, T. Krause and L. J. Gooßen, ChemCatChem., 2012,
8, 6201–6204; (d) S. N. Riduan and Y. G. Zhang, Dalton Trans., 2010,
9, 3347–3357; (e) M. Cokoja, C. Bruckmeier, B. Rieger, W. A.
2011, 13, 2402–2405.
4, 484–487.
9 D. Y. Yu, M. X. Tan and Y. G. Zhang, Adv. Synth. Catal., 2012, 354,
969–974.
5
0
5
0
5
0
5
0
5
0
5
0
5
0
Herrmann and F. E. Kühn, Angew. Chem. Int. Ed., 2011, 50, 8510–
8
2
2
537; (f) K. Huang, C. L. Sun and Z. J. Shi, Chem. Soc. Rev., 2011, 40,
435–2452; (g) M. Aresta, A. Dibenedetto and A. Angelini, Chem. Rev., 80 11 (a) F.T. Edelmann, Chem. Soc. Rev., 2009, 38, 2253–2268; (b) F. T.
014, 114, 1709–1742.
10 D. Y. Yu and Y. G. Zhang, Green Chem., 2011, 13, 1275–1279.
Edelmann, Chem. Soc. Rev., 2012, 41, 7657–7672; (c) S. L. Zhou, Z.
S. Wu, J. W. Rong, S. W. Wang, G. S. Yang, X. C. Zhu and L. J.
Zhang, Chem. Eur. J., 2012, 18, 2653–2659; (d) T. S. Li, J. Jenter and
P. W. Roesky, Z. Anorg. Allg. Chem., 2010, 636, 2148–2155; (e) C.
Liu, S. L. Zhou, S. W. Wang, L. J. Zhang and G. S. Yang, Dalton
Trans., 2010, 39, 8994–8999; (f) S. Yang, X. C. Zhu, S. L. Zhou, S.
W. Wang, Z. J. Feng, Y. Wei, H. Miao, L. P. Guo, F. H. Wang, G. C.
Zhang, X. X. Gua and X. L. Mu, Dalton Trans., 2014, 43, 2521–2533;
(g) X. C. Zhu, S. W. Wang, S. L. Zhou, Y. Wei, L. J. Zhang, F. H.
Wang, Z. J. Feng, L. P. Guo and X. L. Mu, Inorg. Chem., 2012, 51,
7134–7143; (h) C. AlonsoꢀMoreno, A. Antinlo, F. Carrilloꢀ
Hermosillaa and A. Oterob, Chem. Soc. Rev., 2014, 43, 3406–3425; (i)
B. Liu, T. Roisnel, J. F. Carpentier and Y. Sarazin, Chem. Eur. J.,
2013, 19, 13445 –13462; (j) W. L. Xie, H. F. Hu and C. M. Cui,
Angew. Chem. Int. Ed., 2012, 51, 11141–11144; (k) L. J. Zhang, J.
Xia, Q. H. Li, X. H. Li and S. W. Wang, Organometallics, 2011, 30,
375–378; (l) Y. Chen, H. B. Song and C. M. Cui, Angew. Chem. Int.
Ed., 2010, 49, 8958–8961; (m) Y. J. Wu, S. W. Wang, X. C. Zhu, G.
S. Yang, Y. Wei, L. J. Zhang and H. B. Song, Inorg. Chem., 2008, 47,
5503–5511; (n) M. R. Bürgstein, H. Berberich and P. W. Roesky,
Chem. Eur. J., 2001, 7, 3078–3085; (o) J. Chen, Y. B. Wang and Y. J.
Luo, Chin. J. Chem., 2013, 31, 1065–1071.
2
(a) S. Bontemps, L. Vendier and S. SaboꢀEtienne, J. Am. Chem. Soc.,
2014, 136, 4419–4425; (b) A. C. Kathalikkattil, D. W. Kim, J. Tharun,
H. G. Soek, R. Roshan and D. W. Park, Green Chem., 2014, 16, 1607–
1
1
2
2
3
3
4
4
5
5
6
6
7
1
616; (c) X. L. Meng, Y. Nie, J. Sun, W. G. Cheng, J. Q. Wang, H. Y.
85
90
95
He and S. J. Zhang, Green Chem., 2014, 16, 2771–2778; (d) Y. F. Zhao,
B. Yu, Z. Z. Yang, H. Y. Zhang, L. D. Hao, X. Gao and Z. M. Liu,
Angew. Chem. Int. Ed., 2014, 53, 5922–5925; (e) T. Ema, Y. Miyazaki,
T. Taniguchi and J. Takada, Green Chem., 2013, 15, 2485–2492; (f) S.
G. Esfahani, H. B. Song, E. Păunescu, F. D. Bobbink, H. Z. Liu, Z. F.
Fei, G. Laurenczy, M. Bagherzadeh, N. Yana and P. J. Dyson, Green
Chem., 2013, 15, 1584–1589; (g) M. Aresta, A. Dibenedetto and A.
Angelini, Chem. Rev., 2014, 114, 1709–1742; (h) Z. Z. Yang, L. N. He,
J. Gao, A. H. Liu and B. Yu, Energy Environ. Sci., 2012, 5, 6602–6639;
(
(
i) L. Q. Gu and Y.G. Zhang, J. Am. Chem. Soc., 2010, 132, 914–915;
j) T. Sakakura and K. Kohno, Chem. Commun., 2009, 1312–1330; (k)
S. N. Riduan, Y. G. Zhang and J. Y. Ying, Angew. Chem. Int. Ed.,
2009, 48, 3322–3325; (l) J. Qin, P. Wang, Q.Y. Li, Y. Zhang, D. Yuan
and Y. M. Yao, Chem. Commun., 2014, 50, 10952–10955; (m) M. R.
Reithofer, Y. N. Sum and Y. G. Zhang, Green Chem., 2013, 15, 2086– 100
2
2
Luo and X. B. Lu, Chem. Sci., 2012, 3, 2094–2102; (p) C. J. Whiteoak,
N. Kielland, V. Laserna, E. C. EscuderoꢀAdán, E. Martin and A. W.
Kleij, J. Am. Chem. Soc., 2013, 135, 1228–1231; (q) H. A. Duong, P. B. 105
Huleatt, Q. W. Tan and E. L. Shuying, Org. Lett., 2013, 15, 4034–4037;
090; (n) M. North and R. Pasquale, Angew. Chem. Int. Ed., 2009, 48,
946–2948; (o) W. M. Ren, G. P. Wu, F. Lin, J. Y. Jiang, C. Liu, Y.
12 (a) L. J. E. Stanlake, J. D. Beard and L. L. Schafer, Inorg. Chem., 2008,
47, 8062–8068; (b) Q. W. Wang, F. R. Zhang, H. B. Song and G. F.
Zi, J. Organomet. Chem., 2011, 696, 2186–2192; (c) J. A. Thomson
and L. L. Schafer, Dalton Trans., 2012, 41, 7897–7904; (d) L. J. E.
Stanlake and L. L. Schafer, Organometallics. 2009, 28, 3990–3998; (e)
X. L. Hu, C. R. Lu, B. Wu, H. Ding, B. Zhao, Y. M. Yao and Q. Shen,
J. Organomet. Chem., 2013, 732, 92–101; (f) H. Ding, C. R. Lu, X. L.
Hu, B. Wu, B. Zhao and Y. M. Yao, Synlett, 2013, 24, 1269–1274. (g)
L. Zhao, H. Ding, B. Zhao, C. R. Lu and Y. M. Yao, Polyhedron,
2014, 83, 50–59.
(
r) B. Miaoa and S. M. Ma, Chem. Commun., 2014, 50, 3285–3287; (s)
I. I. F. Boogaerts and S. P. Nolan, J. Am. Chem. Soc., 2010, 132, 8858–
859; (t) W. Z. Zhang, W. J. Li, X. Zhang, H. Zhou and X. B. Lu, Org.
8
Lett., 2010, 12, 4748–4751; (u) I. I. F. Boogaerts, G. C. Fortman, M. R. 110
L. Furst, C. S. J. Cazin and S. P. Nolan, Angew. Chem. Int. Ed., 2010,
4
Angew. Chem. Int. Ed., 2010, 49, 8670–8673; (w) X. Zhang, W. Z.
Zhang, L. L. Shi, C. X. Guo, L. L. Zhang and X. B. Lu, Chem.
Commun., 2012, 48, 6292–6294; (x) W. L. Wang, G. D. Zhang, R. 115
Lang, C. G. Xia and F. W. Li, Green Chem., 2013, 15, 635–640; (y) Z.
Z. Yang, L. N. He, S. Y. Peng and A. H. Liu, Green Chem., 2010, 12,
1850–1854;
http://dx.doi.org/10.1016/j.ccr.2014.09.002.
(a) Z. W. Zhang and X. B. Lu, Chin. J. Catal., 2012, 33, 745–756; (b) F. 120
Manjolinho, M. Arndt, K. Gooßen and L. J. Gooßen, ACS Catal., 2012,
9, 8674–8677; (v) L. Zhang, J. H. Cheng, T. Ohishi and Z. Hou,
13 (a) Wylie W. N. O, X. H. Kang, Y. J. Luo and Z. Hou,
Organometallics, 2014, 33, 1030–1043; (b) K. R. D. Johnson, B. L.
Kamenz and P. G. Hayes, Organometallics, 2014, 33, 3005–3011; (c)
L. Li, C. J. Wu, D. T. Liu, S. H. Li and D. M. Cui, Organometallics,
2013, 32, 3203−3209; (d) Z. J. Feng, X. C. Zhu, S. Y. Wang, S. W.
Wang, S. L. Zhou, Y. Wei, G. C. Zhang, B. J. Deng and X. L. Mu,
Inorg. Chem., 2013, 52, 9549–9556; (e) Z. H. Liang, X. F. Ni, X. Li
and Z. Q. Shen, Dalton Trans., 2012, 41, 2812–2819; (f) S. Yang, Z.
Du, Y. Zhang and Q. Shen, Chem. Commun., 2012, 48, 9780–9782; (g)
X. C. Zhu, S. W. Wang, S. L. Zhou, Y. Wei, L. J. Zhang, F. H. Wang,
Z. J. Feng, L. P. Guo and X. L. Mu, Inorg. Chem., 2012, 51, 7134–
7143; (h) Z. Du, Y. Zhang, Y. M. Yao and Q. Shen, Dalton Trans.,
2011, 40, 7639–7644; (i) Z. Du, H. Zhou, H. S. Yao, Y. Zhang, Y. M.
Yao and Q. Shen, Chem. Commun., 2011, 47, 3595–3597; (j) G. G.
Skvortsov, A. O. Tolpyguin, G. K. Fukin, A. V. Cherkasov and A. A.
Trifonov, Eur. J. Inorg. Chem., 2010, 1655–1662; (k) D. T. Dugah, B.
W. Skelton and E. E. Delbridge, Dalton Trans., 2009, 1436–1445; (l)
M. Konkol, M. Kondracka, P. Voth, T. P. Spaniol and J. Okuda,
Organometallics, 2008, 27, 3774–3784; (m) H. Zhou, H. D. Guo, Y.
M. Yao, L. Y. Zhou, H. M. Sun, H. T. Sheng, Y. Zhang and Q. Shen,
Inorg. Chem., 2007, 46, 958–964; (n) H. D. Guo, H. Zhou, Y. M. Yao,
Y. Zhang and Q. Shen, Dalton Trans., 2007, 3555–3561; (o) C. F. Pi,
R. T. Liu, P. Z. Zheng, Z. X. Chen and X. G. Zhou, Inorg. Chem.,
2007, 46, 5252ꢀ5259; (p) E. E. Delbridge, D. T. Dugah, C. R. Nelson,
B. W. Skelton and A. H. White, Dalton Trans., 2007, 143–153; (q) M.
Y. Deng, Y. M. Yao, Q. Shen, Y. Zhang and J. Sun, Dalton Trans.,
2004, 944–950; (r) H. Y. Ma, T. P. Spaniol and J. Okuda, Dalton
Trans., 2003, 4770–4780.
(z)
Coord.
Chem.
Rev.,
2014,
3
2
, 2014–2021; (c) A. Correa and R. Martin, Angew Chem, Int Ed., 2009,
48, 6201–6204; (d) D. Bonne, M. Dekhane and J. Zhu, Angew Chem,
Int Ed., 2007, 46, 2485–2488; (e) F. Lehmann, L. Lake, E. A. Currier,
R. Olsson, U. Hacksell and K. Luthman, Eur. J. Med. Chem., 2007, 42, 125
2
76–285; (f) B. Yu, Z. F. Diao, C. X. Guo, C. L. Zhong, L. N. He, Y. N.
Zhao, Q. W. Song, A. H. Liu and J. Q. Wang, Green Chem., 2013, 15,
2401–2407.
(a) H. Arakawa et al., Chem. Rev. 2001, 101, 953–996; (b) J. Stohrer, E.
Fritzꢀlanghals and C. Brüninghaus, U. S. Patent., 2007, 7,173,149B2; (c) 130
J. Tsuji, M. Takahashi and T. Takahashi, Tetrahedron Lett., 1980, 21,
4
8
49–850; (d) E. R. H. Jones, G. H. Whitham and M. C. Whiting, J.
Chem. Soc., 1957, 4628–4633; (e) N. Satyanarayana and H. Alper,
Organometallics, 1991, 10, 804–807; (f) J. Li, H. Jiang and M. Chen,
Synth. Commun.,2001, 31, 199–202; (g) Y. Izawa, I. Shimizu and A. 135
Yamamoto, Bull, Chem. Soc. Jpn., 2004, 77, 2033–2045; (h) T. Mizuno
and H. Alper, J. Mol. Catal. A–Chemical., 1997, 123, l–24; (i) H.
Arzoumanian, F. Cochini, D. Nuel, J. F. Petrignani and N. Rosas,
Organometallics, 1992, 11, 493–495; (j) T. Sakakura and K. Kohon,
Chem. Commun., 2009, 1312–1330; (k) T. Sakakura, J.ꢀC. Choi and H. 140
Yasuda, Chem. Rev., 2007, 107, 2365–2387; (l) N. Eghbali and C. J. Li,
Green Chem., 2007, 9, 213–215.
14 F. R. Zhang, J. X. Zhang, H. B. Song and G. F. Zi, Inorg. Chem.
Commun., 2011, 14, 72–74.
15 S. P. Anthony, K. Basavaiah and T. P. Radhakrishnan, Cryst. Growth.
Des., 2005, 5, 1663–1665.
5 L. J. Gooßen, N. Rodríguez, F. Manjolinho and P. P. Lange, Adv. Synth.
Catal., 2010, 352, 2913–2917.
6
7
D. Y. Yu and Y. G. Zhang, PNAS, 2010, 107, 20184–20189.
X. Zhang, W. Z. Zhang, X. Ren, L. L. Zhang and X. B. Lu, Org. Lett.,
145 16 G. M. Sheldrick, SHELXLꢀ97, Program for the Refinement of Crystal
Structures, University of Göttingen, Germany, 1997.
6
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Page 7 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C4GC02200A
Graphic Abstract
Carboxylation of Terminal Alkynes with Carbon Dioxide Catalyzed
by Bridged Bis(amidate) Rare-Earth Metal Amides
†
,†
†
†
Hao Cheng, Bei Zhao,* Yingming Yao , Chengrong Lu
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical
Engineering and Materials Science, Dushu Lake Campus, Soochow University, Suzhou 215123, China
†
t-Bu
O
O
N
t-Bu
(
TMS)2N
Nd
O
N
N
O
N
Nd
t-Bu
O
N(TMS)2
t-Bu
O
cat. 2
Three bis(amidate) rare-earth metal amides {LRE[N(SiMe
which were prepared by the treatment of the bridged amide proligand H2L
N,N'-(cyclohexane-1,2-diyl)bis(4-tert-butylbenzamide) with RE[N(SiMe in THF, had been
)
3 2
]⋅THF}
2
(RE = La(1), Nd(2), Y(3)),
(
3 2 3
) ]
characterized by single-crystal X-ray diffraction, elemental analyses, and NMR for complexes 1
and 3. All the complexes were found as efficient catalysts for the direct carboxylation of terminal
2
alkynes with CO at ambient pressure for the first time. A series of terminal alkynes with good
functional group tolerance were converted to the corresponding propiolic acids in high to excellent
yields using the highest reactive Nd-based catalyst 2 at 40 °C.