10850
J. Am. Chem. Soc. 1999, 121, 10850-10851
Palladium(0)-Catalyzed Cope Rearrangement of
Acyclic 1,5-Dienes. Bis(π-allyl)palladium(II)
Intermediate
Table 1. Palladium-Catalyzed Allylation of Activated Olefins 1
with Allyl Ethylcarbonatea
entry
1
temp (˚C)
yield (%)b
ratio of adducts ( 2:3:4 )
1c
2
3
1a
1a
1b
1c
1d
1e
1f
1g
1a
1b
1c
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
50
50
50
82 (11)
quant
quant
quant
92
85
quant
88
68:24:8
78:0:22
76:0:24
72:0:28
86:0:14
73:13:14
83:0:17
100:0:0
0:11:89
0:8:92
Hiroyuki Nakamura, Hideki Iwama, Masateru Ito, and
Yoshinori Yamamoto*
4
Department of Chemistry, Graduate School of Science
5
6
d
Tohoku UniVersity, Sendai 980-8578, Japan
7
8
9
0
1
ReceiVed June 22, 1999
76 (10)
97
75 (21)
1
1
Since the earlier examples of Pd(II)-mediated Cope rearrange-
0:16:84
1
2
ment studied by Jonassen and Heimbach, and the first Pd(II)-
3
a
catalyzed version developed by Overman, the transition metal
Unless otherwise specified, 2.5 equiv of allyl ethyl carbonate were
used for the reaction. b Isolated yield based on 1. The recovery yields
catalyzed [3,3]-sigmatropic rearrangement becomes one of the
c
4
of 1 are shown in parentheses. d One equivalent of allyl ethyl carbonate
important transformations in modern organic synthesis. Detailed
was used for this experiment. One regioisomer was obtained in each
adduct.
mechanistic studies on the Pd(II)-catalyzed rearrangements re-
vealed that the reaction proceeds via a palladium-bound six-
membered carbenium ion intermediate (route a in Scheme 1).3
,5
2
,3-dimethyl-3-phenyl-1,5-heptadiene.3b We now report the first
example for the palladium(0)-catalyzed Cope rearrangement of
certain 1,5-hexadienes, which proceeds through the bis(η -allyl)-
Scheme 1. Palladium-Catalyzed Cope Rearrangement
3
Pd(II) intermediate (route b) formed by the Pd(0) insertion into
a nonstrained C-C bond (Scheme 1).
We previously reported the palladium(0)-catalyzed alkoxyal-
10
lylation of trisubstituted activated olefins with allylic carbonates;
in these experiments the two substituents at the â-position of
1
1
activated olefins were H and aryl, or H and tert-butyl. On the
way to further development of this pronucleophile addition
reaction, an interesting C-H activation reaction was found when
we used tetra-substituted activated olefins 1 whose â-substituents
were aryl and methyl, tert-butyl and methyl, or aryl and ethyl.
The results are summarized in Table 1 and eq 1. The reaction of
As an alternative mechanism, oxidative addition of the allylic
3
IV
6
2
C-C bond to form bis(η -allyl)Pd Cl was proposed. This
proposal is very interesting from the viewpoint of the present
day importance for C-C bond activation, since the proposed
7
process involves the Pd(II) insertion into a nonstrained and
nonfunctionalized C-C bond.8 However, the proposed mecha-
nism was not operative in the Pd(II)-promoted rearrangement due
to the lack of products of [1,3]-rearrangement and to the strict
,9
2
chair topography of the PdCl -catalyzed rearrangement of (3R,5E)-
(
1) Trebellas, J. C.; Olechowski, J. R.; Jonassen, H. B. J. Organomet. Chem.
1
966, 6, 412.
(
2) Heimbach, P.; Molin, M. J. Organomet. Chem. 1973, 49, 477.
(
3) (a) Overman, L. E.; Knoll, F. M. J. Am. Chem. Soc. 1980, 102, 865.
(
b) Overman, L. E.; Jacobsen, E. J. J. Am. Chem. Soc. 1982, 104, 7225. (c)
1
a with allyl ethyl carbonate (1 equiv) proceeded very smoothly
in the presence of Pd(PPh catalyst (5 mol %) at room
temperature for 30 min, giving a 68:24:8 mixture of R-adduct
Bluthe, N.; Malacria, M.; Gore, J. Tetrahedron. Lett. 1983, 1157. (d) Overman,
L. E.; Renaldo. A. F. Tetrahedron. Lett. 1983, 2235. (e) Overman, L. E.;
Renaldo. A. F. Tetrahedron. Lett. 1983, 3757.
3 4
)
(4) (a) Schenck, T. G.; Bosnich, B. J. Am. Chem. Soc. 1985, 107, 2058.
2
a, γ-adduct 3a, and R,γ-adduct 4a in 82% yield along with the
(
b) Overman, L. E. Angew. Chem., Int. Ed. Engl. 1984, 23, 579.
recovered 1a (11%) (entry 1). The alkoxyallylation adduct, which
was the sole product in the previous cases of trisubstituted olefins,
was not obtained at all. The formation of a major product,
R-adduct 2a, can be explained by the γ-proton abstraction-enolate
formation-allylation at the R-position.12 The use of 2.5 equiv of
allyl ethyl carbonate increased the chemical yields very much to
give a 78:22 mixture of 2a and 4a in essentially quantitative yield
without formation of the γ-adduct 3a (entry 2). Under the same
(
5) Overman, L. E.; Renaldo, A. F. J. Am. Chem. Soc. 1990, 112, 3945.
6) Hamilton, R.; Mitchell, T. R. B.; Rooney, J. J. Chem. Commun. 1981,
(
4
56.
10
(7) Recent reviews: (a) Lutz, R. P. Chem. ReV. 1984, 84, 205. (b) Crabtree,
R. H Chem. ReV. 1985, 85, 245. (c) Rybtchinski, B.; Milstein, D. Angew.
Chem., Int. Ed. Engl. 1999, 38, 870.
(8) Catalytic insertion of rhodium complexes into the C-C bond activated
by the strained system: (a) Murakami, M.; Amii, H.; Ito, Y. Nature 1994,
3
70, 540. (b) Murakami, M.; Amii, H.; Shigeto, K.; Ito, Y. J. Am. Chem.
Soc. 1996, 118, 8285. (c) Murakami, M.; Takahashi, K.; Amii, H.; Ito, Y. J.
Am. Chem. Soc. 1997, 119, 9307. Activated by the adjacent carbonyl group:
(d) Jun, C.-H.; Lee, H. J. Am. Chem. Soc. 1999, 121, 880.
(10) Nakamura, H.; Sekido, M.; Ito, M.; Yamamoto, Y. J. Am. Chem. Soc.
1998, 120, 6838.
(9) Catalytic insertion of palladium complexes into the C-C bond activated
by the strained system: (a) Edelbach, B. L.; Lachicotte, R. J.; Jones, W. D.
(11) The activated olefin, whose two substituents at the â-position were H
and pentyl, underwent the proton absorption at the γ-position followed by
allylation at the R-position to give 4,4-dicyano-1,5-decadiene.
(12) (a) Tsuji, J.; Shimizu, I.; Minami, I.; Ohashi, Y. Tetrahedron Lett.
1982, 23, 4809. (b) Tsuji. J.; Shimizu, I.; Minami, I.; Ohashi, Y.; Sugiura, T.;
Takahashi, K. J. Org. Chem. 1985, 50, 1523.
J. Am. Chem. Soc. 1998, 120, 2843. Activated by the functionalized system:
(
b) Nilsson, Y. I. M.; Andersson, P. G.; B a¨ ckvall, J.-E. J. Am. Chem. Soc.
1
993, 115, 6609. (c) Vicart, N.; Gor e´ , J.; Cazes, B. SYNLETT 1996, 850. (d)
Trost, B. M.; Bunt, R. C. J. Am. Chem. Soc. 1998, 120, 70. (e) Nozaki, K.;
Sato, N.; Takaya, H. J. Org. Chem. 1994, 59, 2679.
1
0.1021/ja992117x CCC: $18.00 © 1999 American Chemical Society
Published on Web 11/09/1999