Cobalt-rhodium heterobimetallic nanoparticle-catalyzed synthesis of α,β-unsaturated amides from internal alkynes, amines, and carbon monoxide

Article abstract of DOI:10.1021/ol0706760

The first example of cobalt-rhodium heterobimetallic nanoparticle-catalyzed synthesis of alkenyl amides from alkynes, amines, and carbon monoxide is described.

Full text of DOI:10.1021/ol0706760

ORGANIC
LETTERS
2007
Vol. 9, No. 13
2465-2468
Cobalt
Nanoparticle-Catalyzed Synthesis of
-Unsaturated Amides from Internal
−Rhodium Heterobimetallic
r,â
Alkynes, Amines, and Carbon Monoxide
Ji Hoon Park, Sun Young Kim, Soo Min Kim, and Young Keun Chung*
Intelligent Textile System Research Center, Department of Chemistry, College of
Natural Sciences, Seoul National UniVersity, Seoul 151-747, Korea
ykchung@snu.ac.kr
Received March 20, 2007
ABSTRACT
The first example of cobalt
monoxide is described.
−rhodium heterobimetallic nanoparticle-catalyzed synthesis of alkenyl amides from alkynes, amines, and carbon
R,â-Unsaturated amides are an important class of compounds
because of their biological and insecticidal activities,1 their
presence in the structure of natural products,2 and their role
as a reaction partner in many useful reactions.3 However,
the preparation of R,â-unsaturated amides has scarcely been
reported.4 Only a handful of stoichiometric reactions and a
few catalytic reactions have been disclosed. The most
desirable method for preparing R,â-unsaturated amides would
be a direct carbonylation of alkynes in the presence of
amines, i.e., aminocarbonylation. Many palladium-catalyzed
aminocarbonylation reactions have been reported.5 However,
they use aryl bromides and iodides to generate primary
aromatic amides.6 Very recently, Alper et al. reported7 the
Pd(OAc)2/dppp-catalyzed aminocarbonylation of alkynes
with amines in ionic liquid [bmim][Tf2N] under mild
conditions. However, their catalytic system is effective in
the presence of relatively high CO pressure (200 psi) and is
(4) For a catalytic reaction, see: (a) El Ali, B.; Tijani, J. Appl. Organomet.
Chem. 2003, 17, 921. (b) El Ali, B.; Tijani, J.; El-Ghanam, A. M. J. Mol.
Catal. A: Chem. 2002, 187, 17. For a stoichiometric reaction, see: (c)
Hernandez-Fernandez, E.; Fernandez-Zertuche, M.; Garcia-Barradas, O.;
Munoz-Muniz, O.; Ordonez, M. Synlett 2006, 440. (d) Feuillet, F. J. P.;
Cheeseman, M.; Mahon, M. F.; Bull, S. D. Org. Biomol. Chem. 2005, 3,
2976. (e) Kojima, S.; Hidaka, T.; Ohba, Y. Heteroatom Chem. 2004, 15,
515. (f) Kim, S.; Lim, C. J. Angew. Chem., Int. Ed. 2004, 43, 5378. (g)
Concello´n, J. M.; Bardales, E. Eur. J. Org. Chem. 2004, 1523. (h) Concello´n,
J. M.; Bardales, E. J. Org. Chem. 2003, 68, 9492. (i) Chiacchio, U.;
Rescifina, A.; Chiacchio, M. A.; Romeo, G.; Romeo, R. J. Org. Chem.
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(5) (a) Okura, K.; Kai, H.; Alper, H. Tetrahedron: Asymmetry 1997, 8,
2307. (b) Coperet, C.; Sugihara, T.; Negishi, E.-i. Tetrahedron Lett. 1995,
36, 1771. (c) Trieu, N. D.; Elsevier, C. J.; Vrieze, K. J. Organomet. Chem.
1987, 325, 23. (d) Torri, S.; Okumoto, H.; Sadakane, M.; Xu, L. H. Chem.
Lett. 1991, 1673. (e) Matteoli, U.; Scrivanti, A.; Beghetto, V. J. Mol. Catal.
A: Chem. 2004, 213, 183.
(1) (a) Putt, K. S.; Nesterenko, V.; Dothager, R. S.; Hergenrother, P. J.
ChemBioChem 2006, 7, 1916. (b) Schultz, T. W.; Yarbrough, J. W.; Koss,
S. K. Cell Biol. Toxicol. 2006, 22, 339. (c) Marrano, C.; de Macedo, P.;
Keillor, J. W. Bioorg. Med. Chem. 2001, 9, 1923.
(2) (a) Davies, I. R.; Cheeseman, M.; Niyadurupola, G.; Bull, S. D.
Tetrahedron Lett. 2005, 46, 5547. (b) Moses, J. E.; Baldwin, J. E.; Marquez,
R.; Adlington, R. M.; Cowley, A. R. Org. Lett. 2002, 4, 3731. (c) Toshima,
K.; Arita, T.; Kato, K.; Tanaka, D.; Matsumura, S. Tetrahedron Lett. 2001,
42, 8873. (d) Andersen, R. J.; Coleman, J. E.; Piers, E.; Wallace, D. J.
Tetrahedron Lett. 1997, 38, 317.
(3) (a) Nahm, M. R.; Potnick, J. R.; White, P. S.; Johnson, J. S. J. Am.
Chem. Soc. 2006, 128, 2751. (b) Okitsu, T.; Saito, M.; Tamura, O.; Ishibashi,
H. Tetrahedron 2006, 61, 9180. (c) Shintani, R.; Kitamura, T.; Hayashi, T.
Chem. Commun. 2005, 3213. (d) Takasu, K.; Nishida, N.; Tomimura, A.;
Ihara, M. J. Org. Chem. 2005, 70, 3957. (e) Koltunov, K. Y.; Walspurger,
S.; Sommer, J. Eur. J. Org. Chem. 2004, 4039. (f) Tosaki, S.-y.; Horiuchi,
Y.; Nemoto, T.; Oshima, T.; Shibasaki, M. Chem. Eur. J. 2004, 10, 1527.
(g) Riber, D.; Skrydstrup, T. Org. Lett. 2003, 5, 229.
(6) (a) Wu, X. Y.; Wannberg, J.; Larhed, M. Tetrahedron 2006, 62, 4665.
(b) Wu, X. Y.; Ekegren, J. K.; Larhed, M. Organometallics 2006, 25, 1434.
(c) Takacs, E.; Skoda-Foldes, R.; Acs, P.; Muller, E.; Kokotos, G.; Kollar,
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10.1021/ol0706760 CCC: $37.00
© 2007 American Chemical Society
Published on Web 05/23/2007

ineffective for the aminocarbonylation of internal alkynes.
El Ali et al. reported4a,b a catalytic synthesis of amides by
carbonylation of alkyl alkynes with aniline derivatives by
Pd(OAc)2/dppb under syngas. They also used a high pressure
of CO and used hydrogen gas to generate palladium-hydride
species. Recently, Ryu et al. reported8 the radical-catalyzed
aminocarbonylation of alkynes. Thus, development of a direct
and clean catalytic synthesis of trans-R,â-unsaturated amides
from readily available starting materials is needed. So far,
very limited work4a,b has been done toward carbonylative
coupling of primary and secondary amines with internal
alkynes. Furthermore, heterogeneous catalysts for the amino-
carbonylation are still scarce.9 Thus, the study of amino-
carbonylation of internal alkynes via new heterogeneous
catalysts under relatively low CO pressure is still of interest.
mg) in the presence of a catalytic amount of Co2Rh2 (5 mol
%, 90 mg) in 4 mL of toluene, under 5 atm of CO at 100 °C
for 18 h, gave an amide 3a and a cyclohydrocarbonylated
product 4a in 45% and 7% yields (based on 1a used),
respectively (eq 1). The catalytic cyclohydrocarbonylation
of acetylenes in the presence of Co2Rh2 has already been
reported by us.16d Initially, a furanone, a double carbonylation
product, was always present in the product mixture. However,
addition of molecular sieves to the reaction mixture practi-
cally eliminated this problem. Encouraged by this result, we
screened various reaction conditions, including the CO
pressure, the reaction temperature, the reaction time, and a
catalyst for the aminocarbonylation of 1a and 2a. The result
is summarized in Table 1. A trimerization product, an
Recently, the chemistry of transition-metal nanoparticles
has been rapidly developed10 and their use has widened to
include many catalytic reactions, such as oxidation,11 hy-
drogenation,12 coupling reactions,9b,13 the PKR,14 and some
photocatalytic reactions.15 We found that cobalt/rhodium
nanoparticles (Co2Rh2) derived from Co2Rh2(CO)12 were
quite useful catalysts in PKR-type reactions and related
carbocyclizations.16 In the context of our studies on the use
of transition metal nanoparticles in organic reactions, we
recently found that Co2Rh2 was quite effective for the
aminocarbonylation reaction of disubstituted alkynes in the
presence of amines and carbon monoxide. The catalytic
reaction could be carried out under relatively low CO
pressure (5 atm) and the catalytic system did not require any
additives or promoters such as phosphines or ionic liquids.
This is the first use of transition metal nanoparticles as
catalysts in the aminocarbonylation of alkynes.
Table 1. Optimization of the Co2Rh2-Catalyzed
Aminocarbonylation of 1a with 2aa
entry
catalyst
CO (atm) T (°C) time (h) yieldb (%)
1
2
3
4
5
6
7
8
Co2Rh2 (5 mol %)
Co2Rh2 (5 mol %)
Co2Rh2 (5 mol %)
Co2Rh2 (5 mol %)
Co2Rh2 (5 mol %)
Rh4 (5 mol %)c
Co2 (10 mol %)c
Co2 (5 mol %) +
Rh4 (2.5 mol %)c
10
20
3
5
5
5
5
5
100
130
130
130
130
130
130
130
18
18
18
18
24
24
24
24
53
42
60
69
79
12
N.R.d
trace
a 1.5 mmol of alkyne and 1.0 mmol of amine were used in 4 mL of
toluene. b Based on amine employed. c Rhodium and cobalt nanoparticles
drived from Rh4(CO)12 and Co2(CO)8, respectively. d Reactant recovered.
aromatic compound, was sometimes obtained as a side
product. Thus, the yields in Table 1 were based on the
butylamine used.
Aminocarbonylation was studied using diphenyl acetylene
1a as a model substrate and Co2Rh2 as a catalyst. Treatment
of 1a (1 mmol, 174 mg) with butyl amine 1b (1 mmol, 73
As Table 1 shows, the effect of the CO pressure and the
reaction temperature was noticeable (entries 1-4). Interest-
ingly, there was an optimum CO pressure. An increase of
the reaction time from 18 to 24 h (entry 4 vs 5) also resulted
in a noticeable increase in the yield. For reference purposes,
other relevant transition metal nanoparticles such as Rh and
Co nanoparticles, and a mixture of the two were used as
catalysts (entries 6-8). When the Rh nanoparticles were used
as catalysts (entry 6), the expected product was obtained in
12% yield. However, neither Co nor the Co/Rh mixture was
effective for the aminocarbonylation. Thus, it seemed that
(8) Uenoyama, Y.; Fukuyama, T.; Nobuta, O.; Matsubara, H.; Ryu, I.
Angew. Chem., Int. Ed. 2005, 44, 1075.
(9) Lee, S. I.; Son, S. U.; Chung, Y. K. Chem. Commun. 2002, 1310.
(10) (a) Cushing, B. L.; Kolesnichenko, V. L.; O’Connor, C. J. Chem.
ReV. 2004, 104, 3893. (b) Moreno-Man˜as, M.; Pleixats, R. Acc. Chem. Res.
2003, 36, 638. (c) Zhao, D.; Fei, Z.; Ang, W.-H.; Dyson, P. J. Small 2006,
2, 879.
(11) (a) Wang, S. R.; Huang, J.; Zhao, Y. Q.; Wang, S. P.; Wu, S. H.;
Zhang, S. M.; Hunag, W. P. Mater. Lett. 2006, 60, 1706. (b) Yagi, M.;
Tomita, E.; Sakita, S.; Kuwabara, T.; Nagai, K. J. Phys. Chem. B 2005,
109, 21489.
(12) (a) Fonseca, G. S.; Silveira, E. T.; Gelesky, M. A.; Dupont, J. AdV.
Synth. Catal. 2005, 347, 847.
(15) (a) Yu, H. G.; Yu, J. G.; Cheng, B. J. Mol. Catal. A: Chem. 2006,
253, 99. (b) Cho, J.; Denes, F. S.; Timmons, R. B. Chem. Mater. 2006, 18,
2989.
(16) (a) Park, K. H.; Jung, I. G.; Kim, S.-Y.; Chung, Y. K. Org. Lett.
2003, 5, 4967. (b) Park, K. H.; Chung, Y. K. Synlett 2005, 545. (c) Park,
K. H.; Chung, Y. K. AdV. Synth. Catal. 2005, 347, 854. (d) Park, K. H.;
Kim, S.-Y.; Chung, Y. K. Org. Biomol. Chem. 2005, 3, 395. (e) Park, K.
H.; Jung, I. G.; Chung, Y. K. Synlett 2004, 2541. (f) Park, K. H.; Jung, I.
G.; Chung, Y. K. Org. Lett. 2004, 6, 1183.
(13) Li, Y.; El-Sayed, M. A. J. Phys. Chem. B, 2001, 105, 8938.
(14) (a) Kim, S.-W.; Son, S. U.; Chung, Y. K.; Hyeon, T. Chem.
Commun. 2001, 2212. (b) Son, S. U.; Lee, S. I.; Chung, Y. K.; Kim, S.-
W.; Hyeon, T. Org. Lett. 2002, 4, 277. (c) Son, S. U.; Park, K. H.; Chung,
Y. K. Org. Lett. 2002, 4, 3983. (d) Park, K. H.; Son, S. U.; Chung, Y. K.
Org. Lett., 2002, 4, 4361. (e) Park, K. H.; Son, S. U.; Chung, Y. K. Chem.
Commun. 2003, 1898. (f) Park, J. H.; Kim, S. Y.; Kim, S. M.; Lee, S. I.;
Chung, Y. K. Synlett 2007, 453.
2466
Org. Lett., Vol. 9, No. 13, 2007

some synergistic effects arose between cobalt and rhodium
nanoparticles in the Co2Rh2 nanoparticles. We do not have
a plausible explanation for the exact nature of the synergistic
effects. A similar sygnergistic phenomenon was observed
other heterobimetallic nanoparticle systems.17 Thus, the
optimized reaction conditions were established as follows:
5 mol % of Co2Rh2, alkyne (1.5 mmol), amine (1.0 mmol),
5 atm of CO, 4 mL of toluene, 130 °C, and 24 h.
Table 3. Co2Rh2-Catalyzed Aminocarbonylation of Alkynes
and Aminesa
The recyclability of the Co2Rh2 heterobimetallic nanopar-
ticle catalyst system for the aminocarbonylation of alkynes
was investigated in toluene. Reuse of the catalyst was
performed without any significant loss of its catalytic activity
after six runs.
With optimal conditions in hand, we next investigated the
aminocarbonylation of various alkynes in the presence of a
variety of amines (Table 3). Disubstituted alkynes with
Table 2. Reuse of Co2Rh2 Catalyst for Aminocarbonylation
Reaction of 1a with 2aa
a 1.5 mmol of 1a, 1.0 mmol of 2a, and 5 mol % of Co2Rh2 catalyst
were used at 130 °C for 24 h in 4 mL of toluene.
dialkyl, alkyl aryl, and diaryl termini were good substrates.
When dialkyl-substituted symmetric alkynes (entry 1 and 2)
were used, the expected products were isolated in 85% and
64% yields, respectively. Treatment of unsymmetric alkynes
led to isolation of two isomeric amides in a ratio of 1.2:1-
1.5:1 depending upon the substituents (entries 3-6). The
overall yields varied greatly depending upon the substituents.
In cases of alkyl,aryl-disubstituted alkynes (entries 3 and 4),
the yields were relatively high (75% and 81% yields,
respectively). However, a relatively lower yield (48%,
respectively) was obtained for diaryl-substituted alkyne with
an electron-donating group (entry 5). In the case of entry 5,
increasing the reaction time to 36 h increased the yield up
to 56%.
a 1.5 mmol of alkyne, 1.0 mmol of amine, and 5 mol % of Co2Rh2
catalyst were used at 130 °C for 24 h in 4 mL of toluene. b Isolated yield.
1
c Product ratio is determined by H NMR spectroscopy. d Reaction time:
36 h.
However, a terminal alkyne such as 1-octyne was not a
good substrate under our reaction conditions (eq 2).
When the aminocarbonylation of dipropylacetylene was
compared to those of diphenylacetylene, relatively high yields
were observed for the aminocarbonylation of dipropyl-
acetylene. Reasonably high yields (50-77%) were obtained
for all primary amines used (entries 6-14). However, a
relatively low yield (24%) was observed for the secondary
amine (entry 15).
In order to obtain insights into the reaction mechanism,
we carried out the following experiments. Treatment of
diphenylacetylene with acetamide or N-methylformamide
yielded no reaction. However, a reaction of benzylamine with
carbon monoxide under our reaction conditions led to
isolation of N-benzylacetamide in 76% yield (eq 3). These
(17) (a) Sinfelt, J. H. Bimetallic catalysts: DiscoVeries, Concepts and
Applications (Exxon Monograph); Wiley: New York, 1983. (b) Yoshikai,
N.; Yamanaka, M.; Ojima, I.; Morokuma, K.; Nakamura, E. Organometallics
2006, 25, 3867. (c) Scott, R. W.; Datye, A. K.; Crooks, R. M. J. Am. Chem.
Soc. 2003, 125, 3708. (d) Chung, Y. M.; Rhee, H. K. Catal. Lett. 2003, 85,
159. (e) David, R. J.; Boudert, M. J. Phys. Chem. 1994, 98, 5471.
Org. Lett., Vol. 9, No. 13, 2007
2467

observations suggested that metal carbonyl species might
react with an amine prior to an alkyne substrate on the
reaction cycle.
the stepwise details for this aminocarbonylation process are
still open to debate and remain subject to investigate in our
lab.18
In conclusion, we have demonstrated that the amino-
carbonylation of alkynes was readily accomplished by
Co2Rh2 heterobimetallic nanoparticles in the presence of 5
atm of CO and amines. Internal alkynes with substituents
such as an alkyl and an aryl were efficiently aminocar-
bonylated, giving the R,â-Unsaturated amides in moderate-
to-high yields. Neither a toxic phosphine/phosphite nor a
corrosive acid was needed for our process. Furthermore, the
Co2Rh2 catalyst is recyclable, and no cyclohydrocarbonylated
byproduct was obtained.
A general mechanistic view has so far remained elusive.
However, a plausible reaction mechanism is shown in
Scheme 1.
Acknowledgment. This work was supported by Grant
No. R01-2005-000-10548-0 from the Basic Research Pro-
gram of the Korea Science & Engineering Foundation
(KOSEF) and by Grant No. R11-2005-065 through the SRC/
ERC Program of MOST/KOSEF We thank Dr. K. H. Park
for his initial study of this project.
Scheme 1. Proposed Reaction Mechanism
Supporting Information Available: Experimental pro-
cedures and spectroscopic data for all new compounds. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OL0706760
(18) Formation of a byproduct 4a suggested that another reaction
mechanism might operate in the catalytic cycle (see below). For general
discussions on the mechanism of aminocarbonylation, see: (a) Joh, T.;
Doyama, K.; Onitsuka, K.; Shiohara, T.; Takahashi, S. Organometallics
1991, 10, 2493. (b) Scrivanti, A.; Beghetto, V.; Campagna, E.; Zanato, M.;
Matteoli, U. Organometallics 1998, 17, 630.
Coordination of carbon monoxide to Co2Rh2 generates I
as an intermediate. Initially, it was expected that CO would
compete with either the alkyne or amine for coordination to
the active metal center in the catalytic cycle. However, the
dependence of the yield upon the CO pressure implied an
initial CO coordination. Insertion of an amine into the metal-
carbon monoxide in I generates intermediate II. Insertion
of alkyne followed by a reductive elimination leads to the
generation of aminocarbonylated product, III, and intermedi-
ate I. While we proposed a plausible reaction mechanism,
2468
Org. Lett., Vol. 9, No. 13, 2007