CO-transfer carbonylation reactions. A catalytic pauson-khand-type reaction of enynes with aldehydes as a source of carbon monoxide

Article abstract of DOI:10.1021/ja0126881

The reaction of enynes with aldehydes in the presence of a catalytic amount of [RhCl(cod)]₂/dppp results in the Pauson-Khand-type reaction without the use of gaseous carbon monoxide to give bicyclic cyclopentenones in high yields (14 examples).

Full text of DOI:10.1021/ja0126881

Published on Web 03/21/2002
CO-Transfer Carbonylation Reactions. A Catalytic Pauson-Khand-Type
Reaction of Enynes with Aldehydes as a Source of Carbon Monoxide
Tsumoru Morimoto,* Koji Fuji, Ken Tsutsumi, and Kiyomi Kakiuchi*
Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Takayama, Ikoma,
Nara 630-0101, Japan
Received December 10, 2001
Scheme 1. Working Hypothesis for CO-Transfer Carbonylation
Transition-metal-catalyzed carbonylation has been a subject of
intense research in the area of organic synthesis and is recognized
as a powerful tool for the direct synthesis of a wide variety of
carbonyl compounds.1 However, the use of highly poisonous carbon
monoxide represents a drawback to this procedure. A carbonylation
reaction without the use of carbon monoxide would make reactions
such as these more desirable and further advance this area. Thus,
we envisioned an approach to this problem in which metal carbonyl
species, which are essential key intermediates in the reaction, could
be generated without the use of carbon monoxide.
Table 1. Catalytic Pauson-Khand-Type Reaction of Enyne 1a
with Aldehydes as a Source of COa
In transition-metal-catalyzed carbonylation reactions, the coor-
dination of carbon monoxide to the metal center results in the
generation of metal carbonyls. Decarbonylation of aldehydes,
mediated by transition metals, also represents an alternative
approach to the formation of metal carbonyls (Scheme 1a).2 If the
material to be carbonylated were introduced into the decarbonylation
system of aldehydes, it would be expected that it would react with
the metal-carbonyl species, formed by the decarbonylation, to
afford the desired carbonylated products. Herein, we wish to report
the verification of our working hypothesis. This study provides, to
our knowledge, the first example of a CO-transfer carbonylation.3
To test our hypothesis, we targeted the Pauson-Khand-type
reaction of enynes (Scheme 1b).4 Although catalytic4,5 and enan-
tioselective6 variants have been developed for this transformation,
it continues to attract considerable attention due to its use in the
preparation of bicyclic cyclopentenones. Most of the catalytic
Pauson-Khand-type reactions of enynes have been conducted under
a high pressure of carbon monoxide,7 similar to other carbonyla-
tions. This encouraged us to develop a catalytic Pauson-Khand-
type reaction of enynes using aldehydes as a carbon monoxide
source without the need for gaseous carbon monoxide.
Our initial studies examined the feasibility of the Rh-catalyzed
CO transfer from benzaldehyde to enyne 1a, because Rh complexes
are known not only to decarbonylate aldehydes2 but also to catalyze
the Pauson-Khand-type reaction of enynes.5d,e,6e,7a,b The reaction
of 1a and benzaldehyde in the presence of a catalytic amount of
[RhCl(cod)]2 and dppp in xylene at 130 °C for 24 h afforded the
desired carbonylated product 2a in 33% isolated yield, along with
65% of unreacted 1a (Table 1, entry 1). This shows that benzal-
dehyde can be used as a carbon monoxide equivalent and that its
CO moiety is incorporated into 2a. Reactions with RhCl(PPh3)3,
RhCl(CO)(PPh3)2, and [RhCl(cod)]2/dppe resulted in lower yields
of 2a, while no carbonylated product was obtained when [RhCl-
(cod)]2 and [RhCl(cod)]2/dppb were used as catalysts.
entry
R
catalyst
yield of 2ab
1
2
3
4
5
6
7
8
Ph
[RhCl(cod)]2/dpppc
33% (65%)
35% (64%)
47% (49%)
61% (38%)
33% (64%)
62% (28%)
20% (78%)
22% (70%)
p-MeO-C6H4
p-CF3-C6H4
C6F5
(E)-Ph-CHdCH
PhCH2CH2
C6F5
[IrCl(cod)]2/BINAPd
e
C6F5
Ru3(CO)12
a Conditions: 1a (0.25 mmol), aldehyde (0.50 mmol), and xylene (2 mL)
at 130 °C for 24 h under N2. b Values in parentheses are the yields of 1a
recovered. c 5 mol % [RhCl(cod)]2 and 11 mol % dppp. d 5 mol %
[IrCl(cod)]2 and 11 mol % BINAP. e 3.3 mol % Ru3(CO)12.
and it was found that the electrochemical nature of aldehydes was
responsible for the CO-transfer catalysis; aldehydes having electron-
withdrawing substituents (entries 3 and 4) donated a CO moiety
more effectively than one having electron-releasing substituents
(entry 2). This is consistent with the general tendency for alkyl
groups to migrate from acyl complexes leading to the formation of
metal-carbonyls.8 An R,â-unsaturated aldehyde could also be used
as a carbon monoxide source; however, its reactivity was lower
than that of C6F5CHO (entry 5). The reaction tolerated the use of
an aldehyde having â-hydrogen, which could serve as a source of
a formyl group3 (entry 6). Interestingly, for all aldehydes tested,
the catalyst abstracted a CO moiety from aldehydes and transferred
them to the enyne, without hydroacylating the alkene and/or the
alkyne portions of the enyne.9 Ir and Ru complexes are also known
to decarbonylate aldehydes10 and to catalyze the Pauson-Khand-
type reaction.11 When they were used as catalysts, CO transfer from
the aldehyde was observed, but the efficiency was inferior to that
found for the Rh catalyst (entries 7 and 8).12
To improve the efficiency of CO transfer, a variety of aldehydes
were examined (Table 1, entries 1-6). All the aromatic aldehydes
tested were able to serve as a carbon monoxide source (entries 1-4),
Various enynes were converted to the corresponding cyclopen-
tenones under the following conditions: enynes (0.50 mmol), C6F5-
CHO (1.0 mmol), and xylene (2 mL) in the presence of [RhCl-
(cod)]2 (0.025 mmol) and dppp (0.055 mmol) at 130 °C under N2.13
* Address correspondence to this author. E-mail: morimoto@ms.aist-nara.ac.jp.
9
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J. AM. CHEM. SOC. 2002, 124, 3806-3807
10.1021/ja0126881 CCC: $22.00 © 2002 American Chemical Society

C O M M U N I C A T I O N S
Table 2. Catalytic CO-Transfer Pauson-Khand-Type Reactionsa
carbon monoxide source without the need for gaseous carbon
monoxide. This represents the first reported example of a CO-
transfer carbonylation. Further studies to address the scope of this
new strategy for other carbonylations are also underway.
Acknowledgment. We thank Ms. Yoshiko Nishiura for as-
sistance in obtaining HRMS.
Supporting Information Available: Experimental details and
characterization data (PDF). This material is available free of charge
via the Internet at http://pubs.acs.org.
References
(1) For a general review, see: Colquhoun, H. M.; Thompson, D. J.; Twigg,
M. V. Carbonylation; Plenum Press: New York, 1991.
(2) (a) Tsuji, J. In Organic Syntheses Via Metal Carbonyls; Wender, I., Pino,
P., Eds.; Wiley: New York, 1977; Vol. 2, pp 595-654. (b) Doughty, D.
H.; Pignolet, L. H. In Homogeneous Catalysis with Metal Phosphine
Complexes; Pignolet, L. H., Ed.; Plenum Press: New York, 1983; Chapter
11, pp 343-375. (c) Beck, C. M.; Rathmill, S. E.; Park, Y. J.; Chen, J.;
Crabtree, R. H.; Liable-Sands, L. M.; Rheingold, A. L. Organometallics
1999, 18, 5311 and references therein.
(3) It has been reported that an aliphatic aldehyde having â-hydrogen provides
an alkene with the formyl moiety. (a) Kondo, T.; Akazome, M.; Tsuji,
Y.; Watanabe, Y. J. Org. Chem. 1990, 55, 1286. (b) Lenges, C. P.;
Brookhart, M. Angew. Chem., Int. Ed. Engl. 1999, 38, 3533.
(4) For recent reviews, see: (a) Chung, Y. K. Coord. Chem. ReV. 1999, 188,
297. (b) Brummond, K. M.; Kent, J. L. Tetrahedron 2000, 56, 3263.
(5) For representative recent papers, see: (a) Hicks, F. A.; Kablaoui, N. M.;
Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 5881. (b) Hayashi, M.;
Hashimoto, Y.; Yamamoto, Y.; Usuki, J.; Saigo, K. Angew. Chem., Int.
Ed. 2000, 39, 631. (c) Krafft, M. E.; Bonaga, L. V. R. Angew. Chem.,
Int. Ed. 2000, 39, 3676. (d) Jeong, N.; Seo, S. D.; Shin, J. Y. J. Am.
Chem. Soc. 2000, 122, 10220. (e) Evans, P. A.; Robinson, J. E. J. Am.
Chem. Soc. 2001, 123, 4609.
(6) (a) Hicks, F. A.; Buchwald, S. L. J. Am. Chem. Soc. 1996, 118, 11688.
(b) Hicks, F. A.; Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 7026. (c)
Sturla, S. J.; Buchwald, S. L. J. Org. Chem. 1999, 64, 5547. (d) Hiroi,
K.; Watanabe, T.; Kawagishi, R.; Abe, I. Tetrahedron Lett. 2000, 41, 891.
(e) Jeong, N.; Sung, B. K.; Choi, Y. K. J. Am. Chem. Soc. 2000, 122,
6771. (f) Shibata, T.; Takagi, K. J. Am. Chem. Soc. 2000, 122, 9852.
(7) The catalytic Pauson-Khand-type reaction of enynes has recently been
reported to proceed under carbon monoxide at atmospheric pressure. (a)
Koga, Y.; Kobayashi, T.; Narasaka, K. Chem. Lett. 1998, 249. (b) Jeong,
N.; Lee, S.; Sung, B. K. Organometallics 1998, 17, 3642. (c) Belanger,
D. B.; O’Mahony, D. J. R.; Livinghouse, T. Tetrahedron Lett. 1998, 39,
7637. (d) Belanger, D. B.; Livinghouse, T. Tetrahedron Lett. 1998, 39,
7641. (e) References 5b, 5c, 6d, and 6f.
a Conditions: enyne (0.50 mmol), C6F5CHO (1.0 mmol), [RhCl(cod)]2
(0.025 mmol), dppp (0.055 mmol), and xylene (2 mL) at 130 °C under N2.
b Isolated yield. c Benzaldehyde (5.0 mmol) was used in place of C6F5CHO.
d Diastereomeric ratios were determined by GC. e The value in parentheses
is the yield of the recovered enyne. f Single stereoisomers.
The present reaction is remarkably general and high-yielding (Table
2).14 When the reaction time was prolonged (60 h) until all of 1a
was consumed, a quantitative yield of 2a were obtained (entry 1).
Use of a large excess (10 equiv) of benzaldehyde also resulted in
the formation of 2a in excellent yield (entry 2). The reaction of
aryl-substituted acetylenes afforded the carbonylated products in
higher yields than those of alkyl-substituted acetylenes (entries 1-7,
10, and 11). The reactions of enynes having tethered heteroatoms
such as oxygen and nitrogen proceeded more smoothly than those
of enynes in which the tether consisted of only carbon (entries 1,
6, and 11). Enynes having 1,1- and 1,2-disubstituted alkene portions
reacted smoothly (entries 8 and 9). 1,7-Enynes also were applicable
for this carbonylation and were converted to bicyclo[4.3.0]nonanone
derivatives (entries 12, 14, and 15). For substrates where two groups
were positioned on contiguous carbons of a ring system, the
cyclocarbonylation proceeded diastereoselectively, resulting in the
formation of tricyclic cyclopentenones (entries 13-15).
(8) For a general review of the kinetic and mechanistic studies of the migration
of an R group from the RCO-metal complex, see: Calderazzo, F. Angew.
Chem., Int. Ed. Engl. 1977, 16, 299.
(9) For a recent review of the hydroacylation of alkenes and alkynes, see:
Kakiuchi, F.; Murai, S. In ActiVation of UnreactiVe Bonds and Organic
Synthesis; Murai, S., Ed.; Springer: Berlin, 1999; pp 65-71.
(10) For the Ir complex, see ref 2b. For the Ru complex, see: Domazetis, G.;
Tarpey, B.; Dolphin, D.; James, B. R. J. Chem. Soc., Chem. Commun.
1980, 939.
Last, the CO moiety on an aldehyde was found to transfer
efficiently to an enyne. The reaction of enyne 1a (0.500 mmol)
with 2-naphthaldehyde (1.00 mmol) afforded the carbonylated
product 2a (0.441 mmol) in 88% yield, along with the decarbo-
nylated product, naphthalene (0.517 mmol), and unreacted aldehyde
(0.414 mmol) (eq 1). The majority of the CO moiety that had been
abstracted from the aldehyde was utilized in the carbonylation step.15
This indicates that, in the present carbonylation system, a cascade
sequence involving decarbonylation and carbonylation proceeds
with negligible loss of the CO moiety, as shown in Scheme 1.
In conclusion, we report on a successful transition metal-
catalyzed Pauson-Khand-type reaction using aldehydes as the
(11) For the Ir complex, see ref 6f. For the Ru complex, see: (a) Morimoto,
T.; Chatani, N.; Fukumoto, Y.; Murai, S. J. Org. Chem. 1997, 62, 3762.
(b) Kondo, T.; Suzuki, N.; Okada, T.; Mitsudo, T. J. Am. Chem. Soc.
1997, 119, 6187.
(12) A combination of [IrCl(cod)]2 with other phosphines such as PPh3, dppe,
dppp, and dppb resulted in the formation of trace amounts of 2a.
(13) The CO-transfer reaction proceeded even at lower temperature (110 °C)
to give 33% of 1a for 24 h.
(14) All new compounds were characterized by NMR, IR, and mass spectral
data, as well as by high-resolution mass spectra. See Supporting
Information.
(15) It is unclear whether the rest of the carbonyl moiety that is abstracted
from the aldehyde is used for other transformations or removed from the
reaction system. We postulate that a portion is present on the rhodium
metal, in the form of a carbon monoxide ligand.
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