Decarbopalladation of π-allylpalladium intermediates formed from palladium-catalyzed arylations of 3-allen-1-ols

Article abstract of DOI:10.1021/ol026659m

eqution presented Unusual palladium-catalyzed arylative fragmentations of acyclic 3-allen-1-ols were observed. Oxidative addition of Pd(0) to aryl halides would form the arylpalladium halides, which added to the central carbon of allenes via carbopalladation to form the π-allylpalladium intermediates. The π-allylpalladium intermediates would be reductively eliminated via carbon-carbon cleavage to give the arylated dienes and the α-hydroxyalkylpalladium intermediates, which were further reductively eliminated to the corresponding aldehydes.

Full text of DOI:10.1021/ol026659m

ORGANIC
LETTERS
2002
Vol. 4, No. 19
3325-3327
Decarbopalladation of π-Allylpalladium
Intermediates Formed from
Palladium-Catalyzed Arylations of
3-Allen-1-ols
Chang Ho Oh,* Seung Hyun Jung, Su Youn Bang, and Dai In Park
Department of Chemistry, Hanyang UniVersity, Sungdong-Gu, Seoul 133-791, Korea
changho@hanyang.ac.kr
Received August 2, 2002
ABSTRACT
Unusual palladium-catalyzed arylative fragmentations of acyclic 3-allen-1-ols were observed. Oxidative addition of Pd(0) to aryl halides would
form the arylpalladium halides, which added to the central carbon of allenes via carbopalladation to form the π-allylpalladium intermediates.
The π-allylpalladium intermediates would be reductively eliminated via carbon−carbon cleavage to give the arylated dienes and the
r-hydroxyalkylpalladium intermediates, which were further reductively eliminated to the corresponding aldehydes.
Palladium-catalyzed reactions involving nucleophilic attack
on π-alkene- and π-allylpalladium complexes provide con-
venient and powerful tools for organic synthesis, and a large
number of selective organic transformations have been
reported.1 Compared to alkynes, olefins, and 1,3-dienes,
allenes have attracted considerable interest only in recent
years. Many examples of palladium-catalyzed carbopalla-
dations,2 carbonylations,3 dimerizations,4 oxidations,5 and
hydropalladations6 involving allenes were reported together
with a variety of intramolecular variants.7
Mechanistically, allenes are capable of undergoing 1,2-
addition under palladium catalysis with both electrophiles
and nucleophiles with opposite regioselectivities, where
electrophiles attach to the central carbon and nucleophiles
to the 1- or 3-carbon of the allene.8 In addition to these,
several transition metal catalysts associated with ruthenium,9
titanium,10 and lanthanides11 were developed to mediate a
(5) (a) Jonasson, C.; Horva´th, A.; Ba¨ckvall, J. E. J. Am. Chem. Soc. 2000,
122, 9600. (b) Xiong, H.; Hsung, R. P.; Berry, C. R.; Rameshkumar, C. J.
Am. Chem. Soc. 2001, 123, 7174.
(6) (a) Yamamoto, Y.; Radhakrishan, U. Chem. Soc. ReV. 1999, 28, 199.
(b) Meguro, M.; Yamamoto, Y. J. Org. Chem. 1999, 64, 694. (c) Trost, B.
M.; Gerusz, V. J. J. Am. Chem. Soc. 1995, 117, 5156. (d) Besson, L.; Gore´,
J.; Cazes, B. Tetrahedron Lett. 1995, 36, 3853.
(7) (a) Grigg, R.; Sridharan, V.; Xu, L.-H. J. Chem. Soc., Chem. Commun.
1995, 1903. (b) Grigg, R.; Sridharan, V.; Terrier, C. Tetraedron Lett. 1996,
37, 4221. (c) Grigg, R.; Loganathan, V.; Sridharan, V.; Stevenson, P.;
Sukirthalingam, S.; Worakun, T. Tetrahedron 1996, 52, 11479. (d) Larock,
R. C.; Zenner, J. M. J. Org. Chem. 1995, 60, 482. (e) Larock, R. C.; He,
Y.; Leong, W. W.; Han, X.; Refvik, M. D.; Jenner, J. M. J. Org. Chem.
1998, 63, 6859. (f) Zenner, J. M.; Larock, R. C. J. Org. Chem. 1999, 64,
7312.
(8) For reactions with electrophiles, see: (a) Yang, F.-Y.; Wu, M.-Y.;
Cheng, C.-H. J. Am. Chem. Soc. 2000, 122, 7122. (b) Ma, S.; Zhao, S. J.
Am. Chem. Soc. 1999, 121, 7943. (c) Huang, T.-H.; Chang, H.-M.; Wu,
M.-Y.; Cheng, C.-H. J. Org. Chem. 2002, 67, 99. For reactions with
nucleophiles, see: (d) Yamamoto, Y.; Al-Masum, M.; Fujiwara, N. Chem.
Commun. 1996, 381.
(1) (a) Tsuji, J. Palladium Reagents and Catalysts: InnoVations in
Organic Synthesis; John Wiley & Sons: Chichester, 1995. (b) Ba¨ckvall, J.
E. Metal-Catalyzed Cross Coupling Reactions; Stang, P., Diederich, F., Eds.;
VCH: Weinheim, 1998. (c) Mu¨ller, T. E.; Beller, M. Chem. ReV. 1998,
98, 675.
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(b) Cazes, B. Pure Appl. Chem. 1990, 62, 1867. (c) Gamez, P.; Ariente,
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P. W.; Engels, B. J. Am. Chem. Soc. 2001, 123, 5557.
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10.1021/ol026659m CCC: $22.00 © 2002 American Chemical Society
Published on Web 08/22/2002

variety of transformations of allenes. During our study on
Pd-catalyzed cyclization of allenynes,12 we found an unusual
carbon-carbon cleavage of π-allylpalladium intermediates
(Scheme 1).
Table 1. Palldium-Catalyzed Arylative Fragmentations of
2,2-Dimethyl-1-phenyl-3,4-pentadien-1-ol with Aryl Halides 2
and 3
Scheme 1
entry ArX
Solvents
2a toluene
2a CHCl3
temp (°C)/time (h) product % yield
1
2
reflux/24
reflux/24
reflux/6
110/6
4a
4a
4a
4a
4a
4a
4b
4c
4d
4e
4f
55
45
87
74
62
73
81
85
80
90
89
78
79
81
3
4
2a 1,4-dioxane
2a DMF
5
2a DMSO
110/6
6
2a ethanol
reflux/4
reflux/6
reflux/6
reflux/6
reflux/6
reflux/6
reflux/6
reflux/6
reflux/6
7
8
9
10
11
12
13
14
2b 1,4-dioxane
2c 1,4-dioxane
2d 1,4-dioxane
2e 1,4-dioxane
2f
1,4-dioxane
2g 1,4-dioxane
3a 1,4-dioxane
3b 1,4-dioxane
4g
4a
4b
Here we report these Pd-catalyzed carbon-carbon bond
cleavages of hydroxy-containing π-allylpalladium intermedi-
ates (A).13 It was expected that the initially formed π-allyl-
palladium intermediate might be cyclized with the internal
nucleophile, OH, to form either the oxetane or the oxane
heterocycle,14 but the π-allylpalladium intermediate (A) was
reductively eliminated to form the arylated 1,3-diene product
4 and the aldehyde 5 in excellent yields, respectively (eq 1
and Table 1). First, we examined this reaction in various
solvents using allenol 1a and iodobenzene (2a) in the
presence of K2CO3 (entries 1-6).
Among the various solvents we tested, the highest yield
of the product diene 4a (87%) and its counterpart, benz-
aldehyde (5, 82%), was obtained in refluxing 1,4-dioxane.15
Next, we carried out the Pd-catalyzed arylative fragmenta-
tions with various aryl iodides 2b-e and aryl bromides 2f,g,
3a,b in 1,4-dioxane. The allenol 1a under these conditions
were cleanly coupled separately with 4-iodoanisole (2b),
4-nitroiodobenzene (2c), 4-iodotoluene (2d), and 1-io-
donaphthalene (2e) and subsequently cleaved to the arylated
conjugated dienes 4b-e in 81%, 85%, 80%, and 90% yields,
respectively (entry 7-10). Aryl bromides such as 2-bromo-
naphthalene (2f), 2-bromotoluene (2g), bromobenzene (3a),
and 4-bromoanisole (3b) also worked well to give 4f, 4g,
4a, and 4b in 89%, 78%, 79%, and 81% yields, respectively
(entries 11-14). Note that sterically hindered 2-bromotoluene
also gave the product 4g in high yield (78%), despite its
steric hindrance (entry 12).
Structural variations of the allenol 1 were tested to see
whether the fragmentation of π-allylpalladium intermediates
A might be affected by groups attached to the OH group.
The phenyl group was replaced by H (1b), n-butyl (1c), vinyl
(1d), and alkynyl (1e) for systematic study (eq 2 and Table
2).16 All allenols possessing a hydroxyl group smoothly
underwent the present reactions with iodobenzene (2a) to
give the phenyl-substituted diene 4a and the corresponding
aldehydes. The simple allenol 1b gave a slightly lower yield
(45%) of the product 4a. Allenol 1c also underwent the
present reactions with aryl iodides 2a-d and aryl bromides
3a,b but less efficiently than the phenyl-substrate 1a to the
aryl-substituted dienes 4a-d in 71-88% yields. Allenol 1d
with iodobenzene (2a) gave the products 4a in 69% yield.
Allenol 1e bearing an alkynyl group was less efficient than
the other allenols 1a-d under these conditions to give the
expected products 4 and in some cases (6g) the cyclized
(10) Urabe, H.; Takeda, T.; Hideura, D.; Sato, F. J. Am. Chem. Soc.
1997, 119, 11295.
(11) (a) Arredondo, V. M.; McDonald, F. E.; Marks, T. J. J. Am. Chem.
Soc. 1998, 120, 4871. (b) Arrendondo, V. M.; Tian, S.; McDonald, F. E.;
Marks, T. J. J. Am. Chem. Soc. 1999, 121, 3633.
(12) (a) Oh, C. H.; Yoo, H. S.; Jung, S. H. Chem. Lett. 2001, 1288. (b)
Oh, C. H.; Jung, S. H.; Rhim, C. Y. Tetrahedron Lett. 2001, 42, 8669.
(13) For Pd-catalyzed rearrangement involving a strained carbon-carbon
bond-cleavage, see: (a) Nagao, Y.; Ueki, A.; Asano, K.; Tanaka, S.; Sano,
S.; Shiro, M. Org. Lett. 2002, 4, 455. (b) Yoshida, M.; Sugimoto, K.; Ihara,
M. Tetrahedron Lett. 2000, 41, 5089. (c) Satoh, T.; Jones, W. D.
Organometallics 2001, 20, 2916. (d) Edelbach, B. L.; Lachicotte, R. J.;
Jones, W. D. J. Am. Chem Soc. 1998, 120, 2843. (e) Nishimura, T.; Uemura,
S. J. Am. Chem. Soc. 1999, 121, 11010. (f) Suginome, M.; Matsuda, T.;
Ito, Y. J. Am. Chem. Soc. 2000, 122, 11015. For a Rh-catalyzed C-C bond
cleavage, see: (g) Jun, C.-H.; Lee, H.; Moon, C. W.; Hong, H.-S. J. Am.
Chem. Soc. 2001, 123, 8600. (h) Jun, C.-H.; Lee, H.; Lim, S.-G. J. Am.
Chem. Soc. 2001, 123, 751. (i) van der Boom, M. E.; Liou, S.-Y.; Ben-
David, Y.; Gozin, M.; Milstein, D. J. Am. Chem. Soc. 1998, 120, 13415.
(14) (a) Jonasson, C.; Horva´th, A.; Ba¨ckvall, J.-E. J. Am. Chem. Soc.
2000, 122, 9600. (b) Ma, S.; Li, L. Org. Lett. 2000, 2, 941. (c) Kuwabe,
S.-i.; Torraca, K. E.; Buchwald, S. L. J. Am. Chem. Soc. 2001, 123, 12202.
(d) Larock, R. C.; Veraprath, S.; Lau, H. H.; Fellows, C. A. J. Am. Chem.
Soc. 1984, 106, 5274. (e) Walkup, R. D.; Guan, L.; Kim, Y. S.; Kim, S.
W. Tetrahedron Lett. 1995, 36, 3805.
(15) When K2CO3 was replaced by triethylamine, the reaction did not
occur at all in toluene and 1,4-dioxane even after refluxing for 12 h and a
low conversion in DMF was obtained at 110 °C.
(16) (a) Schuster, H. F.; Coppola, G. M. Allenes in Organic Synthesis;
Wiley: New York, 1984. (b) Pasto, D. J. Tetrahedron 1984, 40, 2805. (c)
Mori, K.; Nukada, T.; Ebata, T. Tetrahedron 1981, 37, 1343.
3326
Org. Lett., Vol. 4, No. 19, 2002

Finally, the methyl substituents in both allenols 8a and
8b did not prevent the arylative fragmentations with iodo-
benzene (2a) to give 9a and 9b in 84% and 78% (an E/Z
mixture of 1:3 ratio) yields, respectively.
Table 2. Arylative Fragmentations of Allenol 1 with Aryl
Halides 2 and 3
allenol
Ar-X
temp (°C)/time (h)
product
% yield
1b
1c
1c
1c
1c
1c
1c
1d
1e
1e
1e
1e
2a
2a
2b
2c
2d
3a
3b
2a
2a
2d
2f
reflux/12
reflux/6
reflux/24
reflux/6
reflux/12
reflux/10
reflux/24
80/14
80/16
80/10
80/10
80/10
4a
4a
4b
4c
4d
4a
4b
4a
4a
4d
4f
4g, 6g
45
88
71
87
71
78
71
69
77
43
47
34, 21
A mechanistic interpretation is proposed as shown in
Scheme 1. Oxidative addition of Pd(0) to aryl halides is now
a generally accepted process to form arylpalladium halides,
whose aryl group added to the central carbon of allene 1 via
carbopalladation to form the intermediate A. The π-allyl-
palladium intermediate A might be decarbopalladated to form
the fragmentation products 4 and R-hydroxyalkylpalladium
intermediate B. The intermediate B can be â-eliminated to
form the carbonyl compound 5 and HPdX species, which
can reform Pd(0) species by reaction with a base.
2 g
In summary, we have shown highly unusual decarbopal-
ladations of π-allylpalladium intermediates formed from
acyclic 3-allen-1-ols. These new reactions involve π-al-
lylpalladium intermediates A, which were reductively elimi-
nated via carbon-carbon cleavage to the arylated dienes and
the resulting R-hydroxyalkylpalladium intermediates B,
which were further reductively eliminated to the correspond-
ing aldehydes (Scheme 1).
products along with some unidentified polymeric products.
Our attention was then paid to the simple allenol 1f. The
arylative fragmentation of the allenol 1f with iodobenzene
(2a), 4-iodoanisole (2b), 4-nitroiodobenzene (2c), and 1-io-
donaphthalene (2e) were carried out under the similar
conditions except the reaction solvent. These reactions
worked better in DMF than in 1,4-dioxane to give the
expected products 7a-e in good yields (eq 3).
Acknowledgment. We wish to acknowledge the financial
support of KOSEF (2001-1-123-001-5), Korea and Center
for Molecular Design and Synthesis (CMDS).
Supporting Information Available: Characterization
data for compounds 4a-g, 6g, 7a,b,c,e, and 9a,b. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OL026659M
Org. Lett., Vol. 4, No. 19, 2002
3327