Rhodium-Catalyzed Coupling Reaction of Salicyl Aldehydes with Alkynes via Cleavage of the Aldehyde C-H Bond

Full text of DOI:10.1021/jo9709458

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J . Org. Chem. 1997, 62, 4564-4565
regarded as a hydroacylation reaction.7,8 We report
herein our new findings that the latter route can be
realized with high efficiency by using a rhodium-based
catalyst system.
Rh od iu m -Ca ta lyzed Cou p lin g Rea ction of
Sa licyl Ald eh yd es w ith Alk yn es via
Clea va ge of th e Ald eh yd e C-H Bon d
The reaction of salicyl aldehyde (1a ) with 4-octyne (2a )
was first examined in the presence of [RhCl(cod)]2 and a
variety of ligands in toluene (5 mL) under nitrogen
(monitored by GLC), the relative amount of 1a , 2a , [RhCl-
(cod)]2 being 2:2:0.01 (in mmol) (eq 1). It was found that,
Ken Kokubo, Kenji Matsumasa,
Masahiro Miura,* and Masakatsu Nomura
Department of Applied Chemistry, Faculty of Engineering,
Osaka University, Suita, Osaka 565, J apan
Received May 29, 1997
The activation of C-H bonds in organic compounds by
transition-metal complexes is currently one of the most
significant subjects in both organic and organometallic
chemistry. An effective strategy to regioselectively ac-
tivate a C-H bond in a given molecule has been known
to introduce a functional group having ligating ability
at an appropriate position of it.1 Recently, a number of
catalytic coupling reactions of aromatic or vinylic com-
pounds bearing carbonyl- or nitrogen-containing groups
with alkenes and/or alkynes involving such a C-H bond
activation mode as the key step have been developed,
especially by using ruthenium and rhodium complexes.2,3
The reaction of acylarenes has also been minutely
described by Murai et al.2b,c
Meanwhile, we have recently reported that salicyl
aldehydes smoothly react with aryl iodides in the pres-
ence of a palladium catalyst and a base to give 2-aroylphe-
nols, demonstrating that the phenolic function can act
as a good anchor for the catalytic intermolecular C-C
coupling via cleavage of the aldehyde C-H bond.4 It was
expected that, if vinyl halides could be used in place of
aryl iodides, 2-alkenoylphenols could also be obtained in
one step: The phenolic compounds are valuable precur-
sors of chromanones and chromones,5,6 whose skeletons
are widely found in naturally occurring compounds, and
a number of them exhibit interesting biological activities.5
However, the reaction using vinyl halides was less
efficient. One of the other possible routes to prepare
2-alkenoylphenols using salicyl aldehydes via the C-H
cleavage is their coupling with alkynes, which may be
by using dppf (0.02 mmol) as ligand and refluxing the
solvent for 24 h, the expected product, (E)-1-(2-hydroxy-
phenyl)-2-propyl-2-hexen-1-one (3), was produced in an
almost quantitative yield, no isomer being accompanied.9
Addition of an inorganic carbonate, Na2CO3 (0.1 mmol),
was also found to significantly enhance the rate of the
reaction, so that it was completed within 0.5 h, while a
tertiary amine, NEt(i-Pr)2, which is effective for the
rhodium-catalyzed hydroacylation of alkenes with acid
anhydrides and molecular hydrogen,10 showed no mean-
ingful effect. Although other bidentate phosphine ligands,
dppe, dppp, and dppb, as well as monodentate ones, PPh3
and tricyclohexylphosphine, could be used in place of
dppf, they were much less effective.9
The reaction of 1a with 2a using the catalyst system
of [RhCl(cod)]2/dppf/Na2CO3 could also be completed in
refluxing benzene in a period of 2.5 h (eq 2); product 3
(99%) also was cleanly isolated by means of flash chro-
(1) For reviews, see: (a) Newkome, G. R.; Puckett, W. E.; Gupta, V.
K.; Kiefer, G. E. Chem. Rev. 1986, 86, 451. (b) Ryabov, A. D. Chem.
Rev. 1990, 90, 403.
(7) While Rh-catalyzed hydroacylation of alkenes with aldehydes has
been well studied, only the intermolecular cases have generally been
efficient,8 and the reaction with alkynes7j,8e has been little known: (a)
Sakai, K.; Ide, J .; Oda, O.; Nakamura, N. Tetrahedron Lett. 1972, 13,
1287. (b) Larock, R. C.; Oertle, K.; Potter, G. F. J . Am. Chem. Soc.
1980, 102, 190. (c) Vora, K. P.; Lochow, C. F.; Miller, R. G. J .
Organomet. Chem. 1980, 192, 257. (d) Okano, T.; Kobayashi, T.;
Konishi, H.; Kiji, J . Tetrahedron Lett. 1982, 23, 4967. (e) Rode, E.;
Davis, M. E.; Hanson, B. E. J . Chem. Soc., Chem. Commun. 1985, 716.
(f) Marder, T. B.; Roe, D. C.; Milstein, D. Organometallics 1988, 7,
1451. (g) Fairlie, D. P.; Bosnich, B. Organometallics 1988, 7, 946. (h)
Wu, X.-M.; Funakoshi, K.; Sakai, K. Tetrahedron Lett. 1992, 33, 6331.
(i) Barnhart, R. W.; Wang, X.; Noheda, P.; Bergens, S. H.; Whelan, J .;
Bosnich, B. J . Am. Chem. Soc. 1994, 116, 1821. (j) Lee, H.; J un, C.-H.
Bull. Korean Chem. Soc. 1995, 16, 1135; Chem. Abstr. 1996, 124,
202420b.
(8) Rh-catalyzed reaction of aldimines with alkenes: (a) Suggs, J .
W. J . Am. Chem. Soc. 1979, 101, 489. (b) J un, C.-H.; Lee, H.; Hong,
J .-B. J . Org. Chem. 1997, 62, 1200. Ru-catalyzed hydroacylation of
alkenes: (c) Isnard, P.; Denise, B.; Sneeden, R. P. A.; Congnion, J . M.;
Durual, P. J . Organomet. Chem. 1982, 240, 285. (d) Kondo, T.;
Akazome, M.; Tsuji, Y.; Watanabe, Y. J . Org. Chem. 1990, 55, 1286.
Ni-catalyzed hydroacylation of alkynes: (e) Tsuda, T.; Kiyoi, T.;
Saegusa, T. J . Org. Chem. 1990, 55, 2554. Very recently, efficient Co-
catalyzed hydroacylation of alkenes has also been reported: (f) Lenges,
C. P.; Brookhart, M. J . Am. Chem. Soc. 1997, 119, 3165.
(2) Carbonyl-directed catalytic reactions: (a) Murai, S.; Kakiuchi,
F.; Sekine, S.; Tanaka, Y.; Kamatani, A.; Sonoda, M.; Chatani, N.
Nature (London) 1993, 366, 529. (b) Murai, S. J . Synth. Org. Chem.
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A.; Sonoda, M.; Chatani, N.; Murai, S. Bull. Chem. Soc. J pn. 1995,
68, 62. (d) Kakiuchi, F.; Tanaka, Y.; Sato, T.; Chatani, N.; Murai, S.
Chem. Lett. 1995, 679. (e) Kakiuchi, F.; Yamamoto, Y.; Chatani, N.;
Murai, S. Chem. Lett. 1995, 681. (f) Sonoda, M.; Kakiuchi, F.;
Kamatani, A.; Chatani, N.; Murai, S. Chem. Lett. 1996, 109. (g) Trost,
B. M.; Imi, K. Davies, I. W. J . Am. Chem. Soc. 1995, 117, 5371.
(3) Nitrogen-directed catalytic reactions: (a) Moore, E. J .; Pretzer,
W. R.; O’Connell, T. J .; Harris, J .; LaBounty, L.; Chou, L.; Grimmer,
S. S. J . Am. Chem. Soc. 1992, 114, 5888. (b) Lim, Y.-G.; Kang, J .-B.;
Kim, Y. H. J . Chem. Soc., Perkin Trans. 1 1996, 2201. (c) Aulwurm,
U. R.; Melchinger, J . U.; Kisch, H. Organometallics 1995, 14, 3385.
(d) Kakiuchi, F.; Yamauchi, M.; Chatani, N.; Murai, S. Chem. Lett.
1996, 111. (e) Chatani, N.; Fukuyama, T.; Kakiuchi, F.; Murai, S. J .
Am. Chem. Soc. 1996, 118, 493.
(4) Satoh, T.; Itaya, T.; Miura, M.; Nomura, M. Chem. Lett. 1996,
823.
(5) For example: (a) Coffey, S. Rodd’s Chemistry of Carbon Com-
pounds, 2nd Ed.; Elsevier: Amsterdam, 1977; Vol. IV, Part E. (b)
Katritzky, A.; Rees, C. W. In Comprehensive Heterocyclic Chemistry;
Boulton, A. J ., Mckillop, A., Eds.; Pergamon Press: Oxford, 1984; Vol.
3, pp 573-883.
(6) (a) Kasahara, A.; Izumi, T.; Ooshima, M. Bull. Chem. Soc. J pn.
1974, 47, 2526. (b) Cullen, W. P.; Donnelly, D. M. X.; Keenan, A. K.;
Keenan, P. J .; Ramdas, K. J . Chem. Soc., Perkin Trans. 1 1975, 1671.
(c) Furlong, J . J . P.; Nudelman, N. S. J . Chem. Soc., Perkin Trans. 2
1988, 1213.
(9) Abbreviations: dppf ) 1,1′-bis(diphenylphosphino)ferrocene,
dppe ) 1,2-bis(diphenylphosphino)ethane, dppp ) 1,3-bis(diphenylphos-
phino)propane, dppb ) 1,4-bis(diphenylphosphino)butane.
(10) Kokubo, K.; Miura, M.; Nomura, M. Organometallics 1995, 14,
4521.
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Communications
J . Org. Chem., Vol. 62, No. 14, 1997 4565
matography on silica gel. Similarly, 3-methoxy- and
5-chlorosalicyl aldehydes 1b and 1c quantitatively re-
acted with 2a to give the corresponding alkenoylphenols
4 and 5, respectively. Note that the reaction using 20
mmol of each of 1b and 2a in refluxing toluene quanti-
tatively proceeded within 2 h, the turnover rate being
approximately estimated to be as high as 500 h-1. The
reaction of 1a with 1,2-diphenylacetylene (2b) also gave
product 6. In contrast to other catalytic C-H/alkyne
coupling reactions,2e,g,3c terminal alkynes, 1-octyne (2c)
and 1-phenylacetylene (2d ), could smoothly react with
1a , giving pairs of regioisomers 7/7′ and 8/8′ in compa-
rable amounts (eq 3). Styrene, however, did not react
with 1a . Good regioselectivities were observed in the
reactions with propargyl alcohols 2e and 2f (eq 4). The
regioisomers of 7-10 and 7′-10′ could be also separated
by column chromatography on silica gel. The reaction
of 1a with 3-acetoxy-1-octyne (2g) predominantly afforded
compound 11 along with minor amounts of some uni-
dentified products (eq 5).
The present reaction may involve initial coordination
of 1 to a chlororhodium(I) species complexed by dppf to
form a 2-formylphenolate complex accompanied by lib-
eration of HCl and then oxidative addition of the alde-
hyde C-H bond to the metal center to give an (aroylhy-
drido)rhodium(III) as the key steps.4,11,12 It should be
noted that 4-hydroxybenzaldehyde and 2-methoxybenz-
aldehyde as well as benzaldehyde itself could not be used
in place of 1a , supporting the above consideration that
coordination of the phenolic oxygen to the metal center
plays a significant role. It was confirmed that addition
of AgOTf or AgClO4 in place of Na2CO3 to the reaction of
1a with 2a , which may generate a cationic rhodium(I)
species, could not enhance the reaction. Thus, the
insoluble solid base seems to effectively remove initially
formed HCl, which could be a poison for the catalysis.
The origin of high efficiency of dppf as ligand, however,
is not definitive at the present stage.
In summary, we have shown that salicyl aldehydes can
readily react with alkynes accompanied by cleavage of
the aldehyde C-H bond in the presence of a catalytic
amount of a rhodium(I) complex to produce synthetically
useful 2-alkenoylphenols.
Ack n ow led gm en t. This work was partly supported
by a Grant-in-Aid for Scientific Research from the
Ministry of Education, Science, Sports, and Culture,
J apan.
(11) Stoichiometric cyclometalation of salicyl aldehydes with Pd, Pt,
and Ni is known: (a) Bryndza, H. E.; Tam, W. Chem. Rev. 1988, 88,
1163. (b) Klein, H.-F.; Bickelhaupt, A.; Lemke, M.; Sun, H.; Brand,
A.; J ung, T.; Ro¨hr, C.; Flo¨rke, U.; Haupt, H.-J . Organometallics 1997,
16, 668.
(12) Rhodium-catalyzed reaction of aroyl chlorides with alkynes that
may involve alkyne insertion to arylchlorhodium(III) species: Kokubo,
K.; Matsumasa, K.; Miura, M.; Nomura, M. J . Org. Chem. 1996, 61,
6941.
Su p p or tin g In for m a tion Ava ila ble: Typical experimen-
tal procedure and characterization data of the new compounds
3-5, 7, 9-11, and 8′-10′ (3 pages).
J O9709458