J. Am. Chem. Soc. 1997, 119, 10549 10550 Catalytic Pauson Khand Reaction in Super Critical
the homogeneous reaction media after completion of the
reaction. The reaction with water soluble ligand bound catalystsin organic/aqueous phase process8 and with perfluorinatedligands bound catalysts in the conventional organic solvent and
Nakcheol Jeong,*,† Sung Hee Hwang,† Youn Woo Lee,‡ and
perfluorinated solvent system are devised for the operational
Meantime, the use of supercritical fluids (Scfs) as reaction
Hanhyo Institutes of Technology 461-6 Chonmingdong
media is becoming an alternative for the reactions in which the
Korea Institute of Science and Technology
previously described options are not suitable. The projected
P.O. Box 131, Cheongryangri, Seoul, 130-650, Korea
advantages of the reactions in supercritical fluids are theincreased reaction rates and selectivities resulting from the high
solubility of reactant gases, rapid diffusion of solutes, weakening
of the solvation around reacting species, and the local clustering
Cocyclization of alkynes with alkenes and carbon monoxide
of reactants or solvents.10 It is also interesting to note, in a
by cobalt leading to cyclopentenones (known as Pauson Khand
practical sense, that those fluids are easily recycled and allow
reaction) has been accepted as one of the most powerful tools
the separation of dissolved compounds by a gradual release of
in the synthesis of cyclopentenones.1 Recent developments in
pressure. Sequential and selective precipitations of the catalyst
Pauson Khand reaction, especially in the 1990s, have been
quite impressive. These include findings of promoters such as
Several recent reports have shown that supercritical CO2 (sc
silica gel,2 tertiary amine N-oxide,3 and DMSO4 for the
CO2) can replace the conventional organic solvents in various
stoichiometric reaction, enantioselective reactions,5 and catalytic
transformations such as radical reactions,11 Diels Alder reac-
versions of the reaction.6 Many variations employing other
tion,12 polymerization,13 homogeneous catalytic hydrocarboxy-
metals are also reported.7 Despite the successful progress and
lation,14 and asymmetric hydrogenations.15
potential implications as an industrial process of this reaction,
Herein, we would like to report our preliminary study of the
the use of this remarkable reaction has been limited only to the
first catalytic Pauson Khand reaction in supercritical fluids.
The catalytic process by dicobalt octacarbonyl had been well
This limitation is mainly attributed to the rather low turnover
conceived since the discovery of the reaction, but it was in quite
number and turnover frequency of the catalytic reaction. More
recent years before it was realized.16 To our experiences in
severe limitations are associated with the practical operational
this field, the control of aggregation status of the catalytic active
difficulties such as removal of the catalyst and solvents from
species played a critical role. We hoped that the catalytic metals
should be well dispersed in Scfs and the chances of the
‡ Korea Institute of Science and Technology.
aggregation of metals would be reduced substantially.
(1) (a) Khand, I. U.; Knox, G. R.; Pauson, P. L.; Watts, W. E.; Foreman,
Our initial studies using dicobalt octacarbonyl as a catalyst
M. I. J. Chem. Soc., Perkin Trans. 1 1973, 977. (b) Pauson, P. L.; Khand,
were mainly focused in sc CO2 since there was a report dealing
I. U. Ann. N. Y. Acad. Sci. 1977, 295, 2. (c) Pauson, P. L. Tetrahedron 1985, 41, 5855. (c) Schore, N. E. Chem. Re . 1988, 88, 1081. (d) Schore,
with a hydroformylation of olefin with a catalytic amount of
N. E. Org. React. 1991, 41, 1. (e) Schore, N. E. In Comprehensi e Organic Synthesis; Trost, B. M., Ed.; Pergamon: Oxford, 1991; Vol. 5, p 1037. (f)
Catalytic intramolecular Pauson Khand reactions were per-
Schore, N. E. In Comprehesi e Organometallic Chemistry II; Hegedus, L.
S., Ed.; Pergamon: Oxford, Exeter, UK, 1995; Vol. 12, pp 703 739.
formed first in sc CO2 by charging a cylindrical stainless steel
(2) (a) Smit, W. A.; Simonyan, S. O.; Tarasov, G. S.; Mikaelian, G. S.;
reactor (80 mL capacity) with a catalyst and enynes followed
Gybin, A. S.; Ibragimov, I. I.; Caple, R.; Froen, O.; Kraeger, A. Synthesis
by pressurization properly with carbon monoxide and carbon
1989, 472. (b) Smit, W. A.; Gybin, A. S.; Shaskov, A. S.; Strychkov, Y.
dioxide. A red homogeneous supercritical phase was obtained
T.; Kyzmina, L. G.; Mikaelian, G. S.; Caple, R.; Swanson, E. D. Tetrahedron Lett. 1986, 27, 1241. (c) Simonian, S. O.; Smit, W. A.; Gybin, A. S.;
upon warming the mixture to 40 °C, and the reaction mixture
Shashkov, A. S.; Mikaelian, G. S.; Tarasov, V. A.; Ibragimov, I. I.; Caple,
was further heated up to an appropriate temperature, and the
R.; Froen, D. E. Tetrahedron Lett. 1986, 27, 1241.
(3) (a) Shambayati, S.; Crowe, W. E.; Schreiber, S. L. Tetrahedron Lett. 1990, 31, 5289. (b) Jeong, N.; Chung, Y. K.; Lee, B. Y.; Lee, S. H.; Yoo,
After much trial experimentations, the range of the required
S.-e. Synlett 1991, 204.
minimal amount of the catalyst and various parameters of the
(4) Chung, Y. K.; Lee, B. Y.; Jeong, N.; Hudecek, M.; Pauson, P. L.
reaction were roughly defined. Table 1 lists the trials to
Organometallics 1993, 12, 220.
(5) (a) Hay, A. M.; Kerr, W. J.; Kirk, G. G.; Middlemiss, D. Organo-
optimize the reaction condition. The required amount of catalyst
metallics 1995, 14, 4986. Bladon, P.; Pauson, P. L.; Brunner, H.; Eder, R.
is about 2 5 mol %6 but it has not been fully optimized. The
J. Organomet. Chem. 1988, 355, 449. Brunner, H.; Niederhuber, A.
reactions under rather low carbon monoxide pressure (1 5 atm)
Tetrahedron; Asymmetry 1990, 1, 711. (b) Park, H.-J.; Lee, B. Y.; Kang, Y. K.; Chung, Y. K. Organometallics 1995, 14, 3104. (c) Stolle, A.; Becker,
frequently led to incompletion of the reaction or low chemical
H.; Salaun, J.; de Meijere, A. Tetrahedron Lett. 1994, 35, 3521. (d) Castro, J.; Soerensen, H.; Riera, A.; Morin, C.; Moyano, A.; Pericas, M. A.; Greene,
(8) Wan, K. T.; Davis, M. E. Nature 1994, 370, 449.
A. E. J. Am. Chem. Soc. 1990, 112, 9388. Poch, M.; Valenti, E.; Moyano,
(9) Horbath, I. T.; Rabai, J. Science 1994, 266, 72.
A.; Pericas, M. A.; Castro, J.; DeNicola, A.; Greene, A. E. Tetrahedron
(10) McHugh, M.; Krukonis, U. Supercritical Fluid Extraction; Butter-
Lett. 1990, 31, 7505. Verdaguer, X.; Moyano, A.; Pericas, M. A.; Riera,
A.; Bernardes, V.; Greene, A. E.; Alvarez-Larena, A.; Piniella, J. F. J. Am.
(11) Kaupp, G. Angew. Chem., Int. Ed. Engl. 1994, 34, 1452. Tanko, J. Chem. Soc. 1994, 116, 2153. Bernardes, V.; Kann, N.; Riera, A.; Moyano,
M.; Blackert, J. F. Science 1994, 263, 203.
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W. J.; Kirk, G. G.; Middlemiss, D. Synlett 1995, 1085. 1994, 67, 1734. Ikushima, Y. J. Phys. Chem. 1992, 96, 2293. Paulatis,
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M. E.; Alexander, G. C. Pure Appl. Chem. 1987, 59, 61. Chem., Int. Ed. Engl. 1990, 29, 1413. (b) Jeong, N.; Hwang, S. H.; Lee,
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L.; Livinghouse, T. J. Am. Chem. Soc. 1996, 118, 2285. Macromolecules 1993, 26, 2663. DeSimone, J. M.; Guan, Z.; Elsbernd,
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10550 J. Am. Chem. Soc., Vol. 119, No. 43, 1997
Trials To Optimize the PKR Condition in Supercritical CO2
Intramolecular Catalytic PKR in Supercritical CO2
Intermolecular Catalytic PKR in Supercritical CO2
also served as a good substrate albeit an eliminated product wasobtained together with the desired one in the presence of aleaving group (entry 3, Table 2).6
Allyl propargyl ether also produced the corresponding product
in excellent yield (entry 4, Table 2), but tosyl and cbz protectedallyl propargyl amine, which were among the best substratesin the conventional catalytic reaction,6b,c remained unreactedunder this condition since they are not reasonably soluble in scCO2 (entry 5, Table 2).
An intermolecular reaction also worked well under this
condition. Phenyl acetylene can couple with norbonadiene
yield (entries 1, 2, and 4, Table 1). Higher reaction temperature
(excess of) to give the bicyclic compound in 87% (entry 1, Table
(90 100 °C) beyond critical temperature (31 °C at 72.9 atm)
3). Biscocyclization of diyne proceeded nicely to furnish the
is necessary for the completion in a reasonable reaction time
bis(bicyclicpentenone) in high yield (entry 2, Table 3).
( 24 h). This reaction mixture requires higher carbon monoxide
These preliminary studies demonstrate the feasibility of
pressure (15 30 atm) to make the catalytic metal species as
conducting transition metal mediated transformations with high
intact as possible. Otherwise, the metal catalyst was deactivated
by that forming of an unidentified white precipitate.
carbonyl under carbon monoxide pressure will be perfectly fit
The scope of the reaction in terms of the substrates was
in this special phase due to their favorable solubility profiles.
determined by employing a standard condition as follows: 2.5
We are further optimizing the related reactions in SCFs to define
mol % dicobalt octacarbonyl along with 30 atm of CO (at 23
the potential of these novel media and devise environmentally
°C) in CO2 (final pressure is 110 120 atm at 36 9 °C) was
heated at 90 95 °C for 24 h, and the results are summarized in
Supporting Information Available: Representative procedures and
The reaction proceeded pretty well regardless of the substitu-
schematic diagram of equipment (3 pages). See any current mastheadpage for ordering and Internet acess instructions.
tion pattern of acetylene. Disubstituted acetylene gave a littlebetter chemical yield (entry 2, Table 2). 1,1′-Disubstituted olefin
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