Coordination modes and catalytic carbonylative [4 + 1] cycloaddition of vinylallenes

Article abstract of DOI:10.1021/om990028n

(Vinylallene)rhodium complexes with three kinds of coordination modes, that is, η²-coordination of the terminal π-bond of the allenyl group, η⁴-coordination of the conjugated diene skeleton, and planar σ²-coordination, were synthesized by ligand substitution of RhCl-(PPh₃)₃ with vinylallenes of specific substitution patterns. Their structures were determined by X-ray crystallography. Coordination preferences can be explained in terms of spatial interactions between the vinylallene substituents and the phosphine ligands as well as effective delocalization of the π-electrons of the endo- and exocyclic double bonds. The structural studies were extended to the development of the rhodium-catalyzed carbonylative [4 + 1] cycloaddition reaction of vinylallenes, affording five-membered carbocycles. With a nonsymmetrical vinylallene, face-selective η⁴-coordination from the less hindered side of the allenyl group was observed. The achievement of [4 + 1] carbonylation can be attributed to (i) the substantial facility of substituted vinylallenes for η⁴-coordination and (ii) the significant contribution of a metallacyclo-3-pentene resonance form to the intermediate complex. A platinum(O) complex also catalyzed the [4 + 1] cycloaddition of vinylallenes as efficiently as rhodium.

Full text of DOI:10.1021/om990028n

1326
Organometallics 1999, 18, 1326-1336
Coor d in a tion Mod es a n d Ca ta lytic Ca r bon yla tive [4 + 1]
Cycloa d d ition of Vin yla llen es
Masahiro Murakami,* Kenichiro Itami, and Yoshihiko Ito*
Department of Synthetic Chemistry and Biological Chemistry, Kyoto University,
Yoshida, Kyoto 606-8501, J apan
Received J anuary 19, 1999
(Vinylallene)rhodium complexes with three kinds of coordination modes, that is, η2-
coordination of the terminal π-bond of the allenyl group, η4-coordination of the conjugated
diene skeleton, and planar σ2-coordination, were synthesized by ligand substitution of RhCl-
(PPh3)3 with vinylallenes of specific substitution patterns. Their structures were determined
by X-ray crystallography. Coordination preferences can be explained in terms of spatial
interactions between the vinylallene substituents and the phosphine ligands as well as
effective delocalization of the π-electrons of the endo- and exocyclic double bonds. The
structural studies were extended to the development of the rhodium-catalyzed carbonylative
[4 + 1] cycloaddition reaction of vinylallenes, affording five-membered carbocycles. With a
nonsymmetrical vinylallene, face-selective η4-coordination from the less hindered side of the
allenyl group was observed. The achievement of [4 + 1] carbonylation can be attributed to
(i) the substantial facility of substituted vinylallenes for η4-coordination and (ii) the significant
contribution of a metallacyclo-3-pentene resonance form to the intermediate complex. A
platinum(0) complex also catalyzed the [4 + 1] cycloaddition of vinylallenes as efficiently as
rhodium.
In tr od u ction
The structures of conjugated-diene-transition-metal
complexes have attracted considerable attention owing
to the great diversity of their binding modes. For
example, most middle-transition-metal- and late-
transition-metal-diene complexes assume conventional
π2-bonded structures.1 Early transition metals prefer
the bent σ2,π-bonded metallacyclo-3-pentene form.2 On
the other hand, planar σ2-bonded metallacyclic com-
plexes are rare.3-5 s-trans binding has been also re-
ported.6
Conjugated dienes which are extended with a cumu-
lated double bond, such as vinylketenes (1; X ) O), also
furnish η4-complexes with interesting structures7 and
reactivities.8 Although vinylallenes (2; X ) C) are
further examples of such cumulated-diene systems,
their complexes have been rare; key examples have been
limited to η4-iron carbonyl complexes prepared directly
from a vinylallene9 and a phenylallene10 or indirectly
via η4-vinylketene complexes.11
In the course of our synthetic study of vinylallenes,12
we were struck by the paucity of vinylallene complexes
(6) (a) Erker, G.; Wicher, J .; Engel, K.; Rosenfeldt, F.; Dietrich, W.;
Kru¨ger, C. J . Am. Chem. Soc. 1980, 102, 6344. (b) Kai, Y.; Kanehisa,
N.; Miki, K.; Kasai, N.; Mashima, K.; Nagasuna, K.; Yasuda, H.;
Nakamura, A. J . Chem. Soc., Chem. Commun. 1982, 191. (c) Okamoto,
T.; Yasuda, H.; Nakamura, A.; Kai, Y.; Kanehisa, N. J . Am. Chem.
Soc. 1988, 110, 5008. (d) Hunter, A. D.; Legzdins, P.; Nurse, C. R.;
Einstein, F. W. B.; Willis, A. C. J . Am. Chem. Soc. 1985, 107, 1791. (e)
Benyunes, S. A.; Green, M.; Grimshire, M. J . Organometallics 1989,
8, 2268.
(7) Geoffroy, G. L.; Bassner, S. L. Adv. Organomet. Chem. 1988, 28,
1.
(8) Reduto dos Reis, A. C.; Hegedus, L. S. Organometallics 1995,
14, 1586 and references therein.
(9) (a) Kerr, C. E.; Eaton, B. E.; Kaduk, J . A. Organometallics 1995,
14, 269. (b) Areces, P.; J eganathan, S.; Okamura, W. H. An. Quim.
1993, 89, 101.
(10) Trifonov, L. S.; Orahovats, A. S.; Trewo, R.; Heimgartner, H.
Helv. Chim. Acta 1988, 71, 551.
(11) Saberi, S. P.; Thomas, S. E. J . Chem. Soc., Perkin Trans. 1 1992,
259.
(12) Murakami, M.; Amii, H.; Takizawa, N.; Ito, Y. Organometallics
1993, 12, 4223.
(1) (a) Elschenbroich, Ch.; Salzer, A. Organometallics, 2nd ed.;
VCH: Weinheim, Germany, 1992; pp 262-265. (b) Pruchnik, F. P.
Organometallic Chemistry of the Transition Elements; Plenum: New
York, 1990; Chapter 8.
(2) (a) Yasuda, H.; Nakamura, A. Angew. Chem., Int. Ed. Engl. 1987,
26, 723. (b) Erker, G.; Kru¨ger, C.; Mu¨ller, G. Adv. Organomet. Chem.
1985, 24, 1.
(3) (a) Barker, G. K.; Green, M.; Howard, J . A. K.; Spencer, J . L.;
Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1978, 1839. (b) Wakatsuki,
Y.; Aoki, K.; Yamazaki, H. J . Chem. Soc., Dalton Trans. 1986, 1193.
(4) Perfluoro-1,3-butadiene complexes: (a) Hitchcock, P. B.; Mason,
R. J . Chem. Soc., Chem. Commun. 1967, 242. (b) Hunt, R. L.;
Roundhill, D. M.; Wilkinson, G. J . Chem. Soc. A 1967, 982. (c)
Roundhill, D. M.; Lawson, D. N.; Wilkinson, G. J . Chem. Soc. A 1968,
845. (d) Hughes, R. P.; Rose, P. R.; Rheingold, A. L. Organometallics
1993, 12, 3109.
(5) Vinylketene complexes: (a) Mitsudo, T.; Watanabe, H.; Sasaki,
T.; Takegami, Y.; Watanabe, Y.; Kafuku, K.; Nakatsu, K. Organome-
tallics 1989, 8, 368. (b) Bleeke, J . R.; Haile, T.; Chiang, M. Y.
Organometallics 1991, 10, 19. (c) Huffman, M. A.; Liebeskind, L. S.
Organometallics 1992, 11, 255.
10.1021/om990028n CCC: $18.00 © 1999 American Chemical Society
Publication on Web 03/06/1999

Coordination and Cycloaddition of Vinylallenes
Organometallics, Vol. 18, No. 7, 1999 1327
of transition metals. This paper describes the synthesis
of (vinylallene)rhodium complexes with three coordina-
tion modes, i.e., η2-coordination of the terminal π-bond
of the allenyl group, η4-coordination of the conjugated
diene system, and planar σ2-coordination. A planar σ2-
complex was also synthesized with platinum. Studies
of the coordination modes of vinylallenes revealed a
strong σ-bond character of the η4-bound vinylallene
complexes. A new catalytic carbonylative [4 + 1] cy-
cloaddition reaction of vinylallenes, forming five-
membered carbocycles, was developed on the basis of
the structural studies on the vinylallene complexes.13
η2-Com p lex Coor d in a ted a t th e Ter m in a l Allen ic
π-Bon d
F igu r e 1. Molecular structure of 4 with the hydrogen
atoms and the solvated methanol omitted for clarity (40%
probability thermal ellipsoids).
Vinylallene 3, having no substituents at the terminal
allenic carbon,14 was treated with RhCl(PPh3)3 in ben-
zene at room temperature. In a manner analogous to
that for a simple allene,15 3 displaced one molecule of
PPh3 on rhodium to afford 4 in 78% isolated yield (eq
1). Recrystallization from CH2Cl2/hexane generated air-
Ta ble 1. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for Com p lex 4
Rh(1)-P(3)
Rh(1)-Cl(2)
Rh(1)-C(10)
Si(5)-C(6)
C(9)-C(10)
2.326(3)
2.376(3)
2.115(10)
1.875(12)
1.393(15)
Rh(1)-P(4)
Rh(1)-C(9)
C(7)-C(6)
C(9)-C(8)
C(8)-C(7)
2.316(3)
2.015(9)
1.346(16)
1.314(13)
1.466(12)
P(3)-Rh(1)-P(4)
P(3)-Rh(1)-C(9)
P(4)-Rh(1)-Cl(2)
P(4)-Rh(1)-C(10)
174.4(1) P(3)-Rh(1)-Cl(2)
90.1(1)
92.6(3)
90.7(3)
166.7(3)
91.2(3)
86.8(1)
92.2(3)
P(3)-Rh(1)-C(10)
P(4)-Rh(1)-C(9)
Cl(2)-Rh(1)-C(9)
Cl(2)-Rh(1)-C(10) 153.7(4) C(9)-Rh(1)-C(10) 39.3(4)
Rh(1)-C(9)-C(8)
Rh(1)-C(9)-C(10)
C(9)-C(8)-C(7)
Rh(1)-C(10)-C(9)
136.2(7) Si(5)-C(6)-C(7)
74.2(6)
129.8(8)
149.6(9)
121.1(9)
C(8)-C(9)-C(10)
126.2(9) C(8)-C(7)-C(6)
66.5(5)
η4-Com p lexes Coor d in a ted a t Tw o Con ju ga ted
π-Bon d s
stable yellow crystals. The molecular structure, char-
acterized by X-ray crystallographic analysis, depicts η2-
coordination at the terminal allenic π-bond (Figure 1;
bond distances and angles are given in Table 1). The
rhodium has a square-planar geometry. The terminal
allenic π-bond binds to rhodium from its less hindered
side, and the trans site is occupied by the chlorine atom.
The η2-bound π-bond axis lies perpendicular to the
square plane. As a consequence of η2-coordination, the
allenyl group is distorted from linearity ( C(8)-C(9)-
C(10) ) 149.6(9)°), and the η2-bound π-bond is longer
(C(9)-C(10) ) 1.393(15) Å) than the free C(8)-C(9)
π-bond (1.314(13) Å). As was observed previously,15 the
distance from rhodium to the central allenic carbon
atom (C(9)-Rh(1) ) 2.015(9) Å) is shorter than the
distance to the terminal allenic carbon (C(10)-Rh(1) )
2.115(10) Å), probably reflecting higher s character in
orbital hybridization on C(9).
Vinylallene 5, having two methyl groups at the allenic
terminus, was reacted with RhCl(PPh3)3 at room tem-
perature for 20 h. In marked contrast to the case for 3,
two molecules of PPh3 were displaced by 5 to yield the
(η4-vinylallene)rhodium(I) complex 6 as a mixture of
endo and exo isomers, which were isolated in 44% and
19% yields, respectively, by chromatography (eq 2).
(13) Preliminary communications: (a) Murakami, M.; Itami, K.; Ito,
Y. Angew. Chem., Int. Ed. Engl. 1995, 34, 2691. (b) J . Am. Chem. Soc.
1996, 118, 11672.
(14) Attempted ligand substitution with a vinylallene unsubstituted
at both of the vinyl and allenyl terminals failed, because such a
vinylallene readily underwent oligomerization.15b
(15) (a) Osborn, J . A. J . Chem. Soc., Chem. Commun. 1968, 1231.
(b) Otsuka, S.; Tani, K.; Nakamura, A. J . Chem. Soc. A 1969, 312. (c)
Kashiwagi, T.; Yasuoka, N.; Kasai, N.; Kukudo, M. J . Chem. Soc.,
Chem. Commun. 1969, 317.
Orange single crystals of endo-6 were obtained from
CH2Cl2/hexane, and the structure was determined by
X-ray crystallography (Figure 2). The rhodium(I) atom
has a distorted-square-planar geometry with the two cis

1328 Organometallics, Vol. 18, No. 7, 1999
Murakami et al.
Ta ble 2. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for Com p lex en d o-6
Rh(1)-P(3)
Rh(1)-C(6)
Rh(1)-C(8)
Si(4)-C(5)
C(6)-C(5)
C(8)-C(9)
2.312(2)
2.196(5)
2.019(5)
1.880(5)
1.415(7)
1.326(6)
Rh(1)-Cl(2)
Rh(1)-C(7)
Rh(1)-C(5)
C(6)-C(7)
C(7)-C(8)
2.346(2)
2.131(5)
2.227(5)
1.448(7)
1.405(7)
P(3)-Rh(1)-Cl(2)
P(3)-Rh(1)-C(7)
P(3)-Rh(1)-C(5)
Cl(2)-Rh(1)-C(7)
Cl(2)-Rh(1)-C(5)
C(6)-Rh(1)-C(8)
C(7)-Rh(1)-C(8)
Rh(1)-C(5)-C(6)
Rh(1)-C(6)-C(5)
Rh(1)-C(7)-C(6)
Rh(1)-C(7)-C(8)
Rh(1)-C(8)-C(9)
Rh(1)-C(5)-Si(4)
C(8)-Rh(1)-C(5)
93.3(1)
103.3(2)
169.5(2)
162.1(2)
93.8(2)
71.6(2)
39.5(2)
70.2(3)
72.6(3)
72.9(3)
65.9(3)
142.2(4)
113.4(3)
83.7(2)
P(3)-Rh(1)-C(6)
P(3)-Rh(1)-C(8)
Cl(2)-Rh(1)-C(6)
Cl(2)-Rh(1)-C(8)
C(6)-Rh(1)-C(7)
C(6)-Rh(1)-C(5)
C(7)-Rh(1)-C(5)
Rh(1)-C(6)-C(7)
C(7)-C(6)-C(5)
Rh(1)-C(8)-C(7)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
Si(4)-C(5)-C(6)
132.4(2)
94.5(2)
123.4(2)
146.8(2)
39.1(2)
37.3(2)
68.9(2)
68.0(3)
119.0(4)
74.6(3)
119.9(5)
142.1(5)
130.2(4)
Ta ble 3. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for Com p lex exo-6
Rh(1)-Cl(2)
Rh(1)-C(8)
Rh(1)-C(7)
Si(4)-C(5)
C(8)-C(7)
C(6)-C(7)
2.333(1)
2.030(3)
2.093(3)
1.885(3)
1.411(4)
1.434(5)
Rh(1)-P(3)
Rh(1)-C(6)
Rh(1)-C(5)
C(6)-C(5)
C(8)-C(9)
2.300(1)
2.183(3)
2.296(3)
1.395(4)
1.321(5)
Cl(2)-Rh(1)-P(3)
Cl(2)-Rh(1)-C(6)
Cl(2)-Rh(1)-C(5)
P(3)-Rh(1)-C(6)
P(3)-Rh(1)-C(5)
C(8)-Rh(1)-C(7)
C(6)-Rh(1)-C(7)
Rh(1)-C(5)-Si(4)
Rh(1)-C(8)-C(7)
C(7)-C(8)-C(9)
Rh(1)-C(6)-C(5)
C(7)-C(6)-C(5)
Rh(1)-C(7)-C(6)
C(7)-Rh(1)-C(5)
90.6(1)
120.0(1)
96.7(1)
137.5(1)
172.6(1)
40.0(2)
39.1(2)
124.1(2)
72.4(2)
148.2(3)
76.3(2)
118.4(3)
73.8(2)
67.1(2)
Cl(2)-Rh(1)-C(8)
Cl(2)-Rh(1)-C(7)
P(3)-Rh(1)-C(8)
P(3)-Rh(1)-C(7)
C(8)-Rh(1)-C(6)
C(8)-Rh(1)-C(5)
C(6)-Rh(1)-C(5)
Rh(1)-C(7)-C(8)
Rh(1)-C(8)-C(9)
Rh(1)-C(6)-C(7)
Rh(1)-C(5)-C(6)
Si(4)-C(5)-C(6)
C(8)-C(7)-C(6)
153.8(1)
158.7(1)
95.5(1)
105.5(1)
70.3(2)
78.5(2)
36.2(1)
67.6(2)
139.2(3)
67.1(2)
67.5(2)
132.0(3)
117.1(3)
F igu r e 2. Molecular structures of endo-6 (upper) and exo-6
(lower). The phenyl groups on the phosphorus atoms, the
hydrogen atoms, and the solvated CH2Cl2 of exo-6 are
omitted for clarity (40% probability thermal ellipsoids).
C6D6. In contrast, exo-6 failed to undergo isomeriza-
tion,16 indicating that exo-6 is thermodynamically fa-
vored, presumably due to steric reasons. A ring-flipping
(flip-envelope) mechanism17 for this thermal endo-exo
isomerization is shown in Scheme 1. Decomplexation of
the double bond of the bent metallacyclic form of endo-6
and a subsequent flip through the planar σ2-bonded
metallacycle 7 generates the η4-complex with an exo
orientation of the trimethylsilyl group. It is likely that,
in the reaction of 5 with RhCl(PPh3)3, simple ligand
substitution results in the initial formation of endo-6
with the original orientation of the silyl group retained
together with free PPh3. A ring-flipping isomerization,
which may be accelerated by the liberated PPh3, sub-
sequently occurs to furnish a mixture of the two isomers.
The observed structural fluxionality of 6 in solution
suggests a considerable contribution from the rhoda-
cyclo-3-pentene resonance form.
sites occupied by the internal allenic π-bond and the
vinylic π-bond. The former π-bond is trans to the
chlorine atom. The two π-bonds are cisoid and lie in a
plane, constituting η4-coordination. The silicon atom,
while staying in the endo position, deviates from this
plane away from the metal with the torsion angle
Si(4)-C(5)-C(6)-C(7) of 52.7°. The Rh-C(8) bond is the
shortest of all the metal-carbon bonds (Table 2),
presumably due to the difference in hybridization of the
orbitals.
On the other hand, recrystallization of exo-6 from
CH2Cl2/hexane afforded yellow crystals suitable for an
X-ray diffraction study, which confirmed an exo orienta-
tion of the trimethylsilyl group (Figure 2; bond distances
and angles are given in Table 3). Interestingly, the
C(5)-Si(4) bond is approximately coplanar with the η4-
coordinating skeleton or, rather, slightly bent toward
the metal center (torsion angle Si(4)-C(5)-C(6)-C(7)
) 170.3°). Otherwise, exo-6 exhibits structural features
analogous to those of endo-6.
(16) Heating of exo-6 for a prolonged time caused decomposition
instead.
(17) (a) Faller, J . W.; Rosan, A. M. J . Am. Chem. Soc. 1977, 99, 4858.
(b) Kru¨ger, C.; Mu¨ller, G.; Erker, G.; Dolf, U.; Engel, K. Organome-
tallics 1985, 4, 215. (c) Eaton, B.; King, J . A., J r.; Vollhardt, K. P. C.
J . Am. Chem. Soc. 1986, 108, 1359. (d) Smith, G. M.; Suzuki, H.;
Sonnenberger, D. C.; Day, V. W.; Marks, T. J . Organometallics 1986,
5, 549. (e) Bu¨rgi, H.-B.; Doubler-Steudle, K. C. J . Am. Chem. Soc. 1988,
110, 4953.
Notably, isolated endo-6 underwent gradual isomer-
ization to exo-6 (t1/2 ) 22.5 h) on standing at 70 °C in

Coordination and Cycloaddition of Vinylallenes
Organometallics, Vol. 18, No. 7, 1999 1329
Sch em e 1a
F igu r e 3. Molecular structure of 9 with the hydrogen
atoms and the solvated methanol omitted for clarity (40%
probability thermal ellipsoids).
a
The ligands on rhodium are omitted for clarity.
P la n a r σ2-Bon d ed Com p lexes
Ta ble 4. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for Com p lex 9
Vinylallene 8, lacking substituents at the vinylic
terminus, was treated with RhCl(PPh3)3 in benzene at
room temperature. The vinylallene 8 displaced one
molecule of PPh3 on the rhodium to afford metallacycle
9 as a solid in 92% isolated yield, for which satisfactory
analytical data were obtained (eq 3).
Rh(1)-Cl(2)
Rh(1)-P(4)
Rh(1)-C(8)
C(5)-C(6)
C(7)-C(8)
2.458(1)
2.374(1)
2.025(4)
1.510(5)
1.452(6)
Rh(1)-P(3)
Rh(1)-C(5)
P(3)-C(18)
C(6)-C(7)
C(8)-C(9)
2.339(1)
2.024(4)
1.835(4)
1.332(6)
1.362(6)
Cl(2)-Rh(1)-P(3)
Cl(2)-Rh(1)-C(5)
P(3)-Rh(1)-P(4)
P(3)-Rh(1)-C(8)
P(4)-Rh(1)-C(8)
Rh(1)-C(5)-C(6)
C(6)-C(7)-C(8)
Rh(1)-C(8)-C(9)
92.9(1)
Cl(2)-Rh(1)-P(4)
Cl(2)-Rh(1)-C(8)
P(3)-Rh(1)-C(5)
P(4)-Rh(1)-C(5)
C(5)-Rh(1)-C(8)
C(5)-C(6)-C(7)
Rh(1)-C(8)-C(7)
C(7)-C(8)-C(9)
92.2(1)
163.1(2)
89.2(1)
89.7(1)
82.0(2)
115.7(3)
113.1(3)
127.3(4)
114.9(2)
174.8(1)
87.5(2)
87.3(2)
111.8(3)
117.4(3)
119.6(3)
exo-6 (127.8°) infers that the most effective conjugation
is between the endocyclic (C(6)-C(7)) and exocyclic
(C(8)-C(9)) double bonds of 9. In fact, the C(7)-C(8)
distance is significantly shorter than the C(5)-C(6)
distance, probably due to the conjugation. This is
consistent with the lengthening of the exocyclic C(8)-
C(9) double bond (1.362(6) Å) as compared with the
corresponding exocyclic double-bond distances in the η4-
bound complexes endo-6 (1.326(6) Å) and exo-6
(1.321(5) Å). The sp2-carbon-metal distance (C(8)-
Rh(1) ) 2.025(4) Å) is identical with the sp3-carbon-
metal distance (C(5)-Rh(1) ) 2.024(4) Å), suggesting
little contribution of metal to olefin π*-back-bonding.18
The most effective delocalization of the π-electrons of
the endo- and exocyclic double bonds can be relevant to
the observed preference for the planar structure with
the vinylallene ligand. In the case of vinylallene 8, the
absence of substituents at the vinylic terminus renders
possible trans coordination of two bulky PPh3 molecules
to rhodium. As a consequence, the 16-electron complex
with a planar structure is formed without coordination
of the C(6)-C(7) double bond. In the case of vinylallene
5, the steric bulk of the trimethylsilyl group at the
vinylic terminus hampers trans coordination of two
PPh3 molecules to rhodium. Instead, formation of the
16-electron complex as a stable species requires internal
coordination of the C(6)-C(7) double bond, leading to
the observed η4-coordination.
Recrystallization from CH2Cl2/methanol gave air-
stable orange crystals as a methanol solvate. The solid-
state structure of 9 was determined by a single-crystal
X-ray diffraction study. An ORTEP diagram of the
molecule is shown in Figure 3; bond distances and
angles are given in Table 4. The most notable feature
of the structure is that the five-membered rhodacyclo-
3-pentene ring constitutes an almost perfect plane. The
maximum deviation from the mean plane is only 0.018
Å. There is no interaction between the C(6)-C(7) double
bond and rhodium. The arrangement of the pentacoor-
dinated rhodium atom can be considered as a flat square
pyramid, or as a distorted-octahedral geometry with one
vacant site over which the C(10) methyl group at the
allenic terminus hangs. The chlorine atom sits trans to
the sp2 carbon atom (C(8); Cl(2)-Rh(1)-C(8)
)
163.1(2)°), and the two PPh3 ligands are also trans. The
C(5)-C(6) and C(7)-C(8) linkages (1.510(5) and
1.452(6) Å, respectively) are longer than C(6)-C(7)
(1.332(6) Å), reflecting the bond order. The dihedral
angle C(6)-C(7)-C(8)-C(9) is 179.2°. Comparison with
the corresponding dihedral angles of endo-6 (140.6°) and
(18) Tanke, R. S.; Crabtree, R. H. Inorg. Chem. 1989, 28, 3444.

1330 Organometallics, Vol. 18, No. 7, 1999
Murakami et al.
complexes remain rare3-5 and are mostly limited to
perfluoro-1,3-butadiene4 and vinylketene complexes.5
The planar vinylallene complexes 9 and 10 provide new
examples, and their isolation lends direct evidence to
the involvement of a planar metallacyclopentene com-
plex in the ring flipping of a η4-diene complex.
[4 + 1] Cycloa d d ition of Vin yla llen es w ith
Ca r bon Mon oxid e
Five-membered carbocycles are common structural
features of a broad range of natural products. A variety
of [3 + 2] cycloaddition reactions have been developed,
providing a versatile synthetic tool for the preparation
of these skeletons.19 The Pauson-Khand reaction pre-
sents another viable synthetic protocol for [2 + 2 + 1]
assemblies.20 Although [4 + 1] cycloaddition is also a
potential means to construct five-membered carbocy-
cles,21 there are only a few examples of [4 + 1] cyclo-
addition reactions catalyzed by transition metals.22,23
The structural fluxionality observed with the (η4-
vinylallene)rhodium complex 6 suggests a considerable
contribution from the rhodacyclo-3-pentene form. Isola-
tion of the stable planar σ2-bonded complex 9 provides
further inference of the significant metallacyclic char-
acter of (η4-vinylallene)rhodium complexes. One impor-
tant ramification of these findings is that incorporation
of carbon monoxide into the conjugated diene skeleton
may possibly result from migratory insertion of carbon
monoxide into the C-Rh σ-bond of the rhodacyclo-3-
pentene species, leading to a [4 + 1] assembly. More-
over, occurrence of η4-coordination of a vinylallene to
rhodium through direct ligand exchange is particularly
attractive because it would offer access to a catalytic
cycle.
On the basis of these considerations, we next inves-
tigated the [4 + 1] cycloaddition reaction of vinylallenes
with carbon monoxide. First, stoichiometric carbonyla-
tion reactions were examined. When a solution of the
(η4-vinylallene)rhodium complex (endo-6) in CH2Cl2 was
stirred at room temperature under atmospheric pres-
sure of carbon monoxide, a [4 + 1] cycloaddition reaction
proceeded cleanly to furnish 2-(alkylidene)cyclopent-3-
en-1-one 11 in 98% isolated yield. A plausible mecha-
nism for this [4 + 1] cycloaddition is shown in eq 5.
Carbon monoxide is introduced into the coordination
sphere of the metal to give a (vinylallene)carbonyl-
rhodium species, which has a contribution from the
rhodacyclo-3-pentene form in solution. Migratory inser-
tion of the carbonyl group into the C-Rh σ-bond of the
F igu r e 4. Molecular structure of 10 with the hydrogen
atoms and the solvated CH2Cl2 omitted for clarity (40%
probability thermal ellipsoids).
Ta ble 5. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for Com p lex 10
Pt(1)-P(2)
Pt(1)-C(4)
C(4)-C(5)
C(6)-C(7)
2.288(2)
2.099(8)
1.50(1)
1.45(1)
Pt(1)-P(3)
Pt(1)-C(7)
C(5)-C(6)
C(7)-C(8)
2.298(2)
2.132(8)
1.34(1)
1.37(1)
P(2)-Pt(1)-P(3)
P(2)-Pt(1)-C(7)
P(3)-Pt(1)-C(7)
Pt(1)-C(4)-C(5)
C(4)-C(5)-C(11)
C(5)-C(6)-C(7)
Pt(1)-C(7)-C(8)
84.45(8)
169.9(2)
105.6(3)
110.9(6)
121.1(8)
119.9(8)
131.8(7)
P(2)-Pt(1)-C(4)
P(3)-Pt(1)-C(4)
C(4)-Pt(1)-C(7)
C(4)-C(5)-C(6)
C(6)-C(5)-C(11)
Pt(1)-C(7)-C(6)
C(6)-C(7)-C(8)
89.3(2)
173.4(2)
80.6(3)
116.5(8)
122.3(9)
110.0(6)
118.0(8)
An equimolar reaction of the vinylallene 8 with a
platinum(0) complex was also examined using Pt(cod)2
(cod ) 1,5-cyclooctadiene). Facile replacement of the cod
ligand with 8 occurred at room temperature to afford a
Pt(vinylallene)(cod) complex. Sequential treatment with
dppe (1,2-bis(diphenylphosphino)ethane) gave the
Pt(vinylallene)(dppe) complex 10, from which colorless
crystals suitable for X-ray crystallography were ob-
tained (eq 4). The crystal structure shown in Figure 4
(19) (a) Little, R. D. In Comprehensive Organic Synthesis; Trost, B.
M., Fleming, I., Eds.; Pergamon Press: New York, 1991; Vol. 5,
Chapter 3.1. (b) Chan, D. M. T. In ref 19a, Chapter 3.2.
(20) Schore, N. E. In ref 19a, Chapter 9.1.
(21) (a) Liebeskind, L. S.; Chidambaram, R. J . Am. Chem. Soc. 1987,
109, 5025. (b) Curran, D. P.; Liu, H. J . Am. Chem. Soc. 1991, 113,
2127. Nitrogen heterocycles: (c) Rigby, J . H.; Qabar, M. J . Am. Chem.
Soc. 1991, 113, 8975. (d) Rigby, J . H.; Cavezza, A.; Ahmed, G. J . Am.
Chem. Soc. 1996, 118, 12848.
(22) (a) Eaton, B. E.; Rollman, B.; Kaduk, J . A. J . Am. Chem. Soc.
1992, 114, 6245. (b) Mandai, T.; Tsuji, J .; Tsujiguchi, Y.; Saito, S. J .
Am. Chem. Soc. 1993, 115, 5865. (c) Sigman, M. S.; Eaton, B. E. J .
Am. Chem. Soc. 1996, 118, 11783. (d) Darcel, C.; Bruneau, C.; Dixneuf,
P. H. Synlett 1996, 218.
(23) For transition metal-catalyzed [4 + 1] cycloaddition of hetero
conjugated systems, such as allenyl ketones and allenyl imines, to give
five-membered heterocycles, see: (a) Sigman, M. S.; Kerr, C. E.; Eaton,
B. E. J . Am. Chem. Soc. 1993, 115, 7545. (b) Sigman, M. S.; Eaton, B.
E. J . Org. Chem. 1994, 59, 7488.
(bond distances and angles are given in Table 5) depicts
planar σ2-coordination of 8, in which the platinum
possesses a square-planar geometry. Similarly to the
rhodium complex 9, the C(4)-C(5) and C(6)-C(7) link-
ages (1.50(1) and 1.45(1) Å, respectively) are longer than
C(5)-C(6) (1.34(1) Å), reflecting the bond order.
Stereochemical fluxionality of s-cis-diene-transition
metal complexes has been often observed and can be
explained by a ring-flipping mechanism.17 Although
implicated as a transitory species in the ring flipping,
examples of thermodynamically stable planar σ2-bonded

Coordination and Cycloaddition of Vinylallenes
Organometallics, Vol. 18, No. 7, 1999 1331
decreased back-bonding, than to a neutral complex. The
cationic complex [Rh(cod)(MeCN)2]BF4 efficiently cata-
lyzed the [4 + 1] cycloaddition of 5. The corresponding
2-alkylidenecyclopent-3-en-1-one 11 was obtained to-
gether with 2-alkylidenecyclopent-4-en-1-one 12′ in an
excellent combined yield (eq 8). It is likely that the
initial product 11 lost the trimethylsilyl group, located
R to both the carbonyl group and the C-C double bond,
through hydrolysis by water present in the reaction
medium to form 12′.
rhodacyclo-3-pentene form ensues. Although it is un-
clear which one of the sp2 or sp3 carbon atoms migrates,
the result reported by Dixneuf et al.22d may favor
migration of the sp2 carbon atom. The subsequent
reductive elimination of rhodium(I) produces 11. The
complexes exo-6 and 9 also underwent similar carbon-
ylative [4 + 1] cycloaddition on treatment with carbon
monoxide (1 atm) in CH2Cl2 (eqs 6 and 7). In the case
When alkyl-substituted vinylallene 13 was used
instead of 5, the corresponding [4 + 1] cycloadduct was
obtained as a mixture of 2-alkylidenecyclopent-3-en-4-
one 14 and isomerized 2-alkylidenecyclopent-4-en-1-one
14′ in only ca. 30% yield (Table 6, entry 1). In pursuit
of a selective and high-yielding catalytic system of wide
generality, we examined the effects of a variety of
reaction conditions using 13 as a model substrate (Table
6). After much experimentation, it was found that the
use of 1,2-bis(diphenylphosphino)benzene (dppbe) as the
phosphorus ligand and TfO- as the counteranion in
DME under 10 atm of CO gave the best result (83%
conversion, 14:14′ ) 92:8, entry 10).
Next, the standard set of reaction conditions using
the isolated complex [Rh(cod)(dppbe)]OTf was applied
to the [4 + 1] cycloaddition of various vinylallenes (Table
7). Carbon monoxide was catalytically incorporated into
substituted vinylallenes in a [4 + 1] assembly mode.
Bicyclic skeletons were constructed by the reactions of
cyclic vinylallenes (entries 8-10).24 The reactions of 21
and 23 proceeded at lower temperatures. In particular,
0.5 mol % of the catalyst efficiently catalyzed the
reaction of 23 (entry 7). It is reasonable to presume that
the catalytic cycle consists of binding of a vinylallene
in an s-cis form to rhodium, then elementary steps
analogous to those involved in eq 5, and subsequent
rebinding of a new vinylallene molecule to rhodium(I).
Vinylallene 31, in which the allenyl group is nonsym-
metrical, gave only one stereoisomer about the geometry
of the exocyclic CdC bond, the structure of which was
of 9, the conjugated cyclopentenone (12′) was produced
as the cycloadduct, probably via transposition of C3-
C4 unsaturation of the primary product (12) through
rhodium-catalyzed double-bond isomerization. In con-
trast, the (η2-vinylallene)rhodium complex 4 afforded no
cycloaddition product under analogous conditions, in-
dicating that η4-coordination is needed for the carbony-
lative [4 + 1] cycloaddition.
On the basis of the auspicious results in the stoichio-
metric reactions, we next endeavored to establish a
catalytic system of this [4 + 1] cycloaddition. Thus, free
vinylallene 5 was treated with a catalytic quantity of
RhCl(PPh3)3 under carbon monoxide (1 atm). Even when
heated at 70 °C, however, 5 remained unreacted and
only a trace amount of 11 was formed. This is possibly
due to an irreversible reaction of the nascent catalytic
species with carbon monoxide to exclude 5 from the
coordination sphere. We next tried the use of a cationic
complex with the expectation that carbon monoxide
would bind less well to a cationic complex, owing to the
1
confirmed by H NMR NOE experiments (eq 9). This
stereoselectivity can be accounted for by assuming face-
selective η4-coordination from the less hindered side of
the vinylallene in an s-cis form and the subsequent
specific disrotatory motion to a rhodacyclo-3-pentene
intermediate. In the case of vinylallene 33, formation
of a small amount of Z-34 was observed (eq 10). The
ratio Z-34:E-34 gradually increased as the reaction
proceeded, suggesting that isomerization of the major
isomer E-34 to Z-34 took place during the reaction
course. In contrast, the vinylallene 3 with an unsubsti-
tuted allenyl group failed to undergo cycloaddition.
(24) A vinylallene that has a cyclopentenyl group instead of a
cyclohexenyl group and is otherwise identical with 25 failed to undergo
the [4 + 1] cycloaddition.

1332 Organometallics, Vol. 18, No. 7, 1999
Murakami et al.
Ta ble 6. Rh od iu m (I)-Ca ta lyzed [4 + 1] Cycloa d d ition of Vin yla llen e 13 w ith CO
entry no.
Rh precursor
liganda
CO press/atm
solvent
conditions
conversn/%
14:14′
1
2
3
4
5
6
7
8
9
[Rh(cod)(MeCN)2]BF4
[Rh(cod)2]PF6
[Rh(cod)2]PF6
[Rh(cod)2]PF6
[Rh(cod)2]PF6
[Rh(cod)2]PF6
[Rh(cod)2]PF6
[Rh(cod)2]PF6
[Rh(cod)2]PF6
[Rh(cod)2]OTf
[Rh(cod)2]OTf
[Rh(cod)2]OTf
1
1
1
1
1
5
5
5
10
10
10
10
toluene
toluene
toluene
toluene
toluene
toluene
DME
toluene
DME
DME
70 °C, 12 h
80 °C, 24 h
80 °C, 24 h
80 °C, 20 h
80 °C, 24 h
60 °C, 4 h
60 °C, 4 h
60 °C, 4 h
60 °C, 15 h
60 °C, 12 h
60 °C, 12 h
60 °C, 12 h
99b
20
91
56
39
75
50
54
78
83
97
97
70:30
90:10
48:52
11:89
60:40
55:45
90:10
68:32
70:30
92:8
dppm
dppe
dppp
dppb
dppe
dppe
dppbe
dppbe
dppbe
dppf
10
11
12
DME
DME
38:62
38:62
PMe2Ph (12 mol %)
a
Abbreviations: dppm ) bis(diphenylphosphino)methane, dppp ) 1,3-bis(diphenylphosphino)propane, dppb ) 1,4-bis(diphenylphos-
b
phino)butane, dppbe ) 1,2-bis(diphenylphosphino)benzene, dppf ) 1,1′-bis(diphenylphosphino)ferrocene. A significant amount of side
products was formed.
allene 5, neither RhCl(PPh3)3 nor cationic Rh(I) com-
plexes catalyzed a similar carbonylation reaction. All
the attempted catalytic carbonylation reactions of other
dienes, including 2,3-dimethyl-1,3-butadiene, 2,3-diphen-
yl-1,3-butadiene, and 1,4-diphenyl-1,3-butadiene, were
unsuccessful. Next, 35 was treated with a stoichiometric
amount of RhCl(PPh3)3 under conditions similar to those
used for the synthesis of the (η4-vinylallene)rhodium
complex 6. However, no ligand displacement with 35
1
was observed by H NMR. This finding suggests that
the achievement of the [4 + 1] carbonylation mentioned
above can be primarily attributed to the substantial
facility of substituted vinylallenes for η4-coordination
through ligand displacement. The significant contribu-
tion from a metallacyclo-3-pentene resonance form is
also relevant to the enhanced reactivity of the vinyl-
allene system. This is probably also the case for the
reported examples of [4 + 1] carbonylation of conjugated
systems containing an allenyl group.22,23
The use of transition metals other than rhodium was
briefly examined. When [Ir(cod)(dppe)]PF6 was used as
the catalyst in the reaction of 13 at 60 °C in DME, only
4% of 14 was produced after 15 h. In contrast, a
platinum(0) complex prepared from Pt(cod)2 and dppbe
efficiently catalyzed the [4 + 1] cycloaddition of vinyl-
allenes (eqs 11 and 12).25
These results can be explained in terms of the prefer-
ence for η4- vs η2-coordination (vide supra).
It is of interest to compare the reactivities of vinyl-
allenes with those of ordinary conjugated dienes. In the
Con clu sion
case of 35, which is the butadiene analogue of vinyl-
In conclusion, three (vinylallene)rhodium complexes
with different coordination modes were directly synthe-
sized by simple ligand displacement of RhCl(PPh3)3 with
(25) Although the reason is unclear, no reaction took place when
Pt(dibenzylideneacetone)2 was used instead of Pt(cod)2.

Coordination and Cycloaddition of Vinylallenes
Organometallics, Vol. 18, No. 7, 1999 1333
Ta ble 7. Rh od iu m -Ca ta lyzed [4 + 1] Cycloa d d ition
vinylallenes demonstrated the potential reactivities of
vinylallenes toward transition-metal catalysts by way
of η4-coordination.26
of Vin yla llen es w ith CO
Exp er im en ta l Section
Gen er a l Con sid er a tion s. Unless otherwise noted, all
materials were obtained from commercial suppliers and used
without further purification. Tetrahydrofuran was distilled
under N2 from sodium diphenylketyl. Toluene, 1,2-dimethoxy-
ethane (DME), and CH2Cl2 were distilled from CaH2. Pt(cod)2
was prepared according to the literature procedure.27
NMR spectra were recorded on Varian VXR-200, Varian
GEMINI-2000, and J EOL J NM-A400 spectrometers. Unless
otherwise noted, 1H, 31P, and, 13C NMR spectra were acquired
in chloroform-d at 200, 80, and 50 MHz, respectively. Optical
rotation was measured with a Perkin-Elmer 243 polarimeter.
Mass spectra were recorded with a J EOL J MS-D300 spec-
trometer. Column chromatography was performed with Wa-
kogel C-200 (Wako Pure Chemical Co.; 200 mesh). Preparative
thin-layer chromatography was performed with silica gel 60
PF254 (E. Merck, Darmstadt, Germany).
P r ep a r a tion of Vin yla llen es. (E)-5-Meth yl-2-p h en yl-1-
(tr im eth ylsilyl)-1,3,4-h exatr ien e (5). To a mixture of PhCH2-
PdCl(PPh3)2 (155 mg, 0.21 mmol) and CuI (82 mg, 0.43 mmol)
in DMF (20 mL) were successively added 3-bromo-3-methyl-
1-butyne (6.0 g, 40.8 mmol) and 1-phenyl-1-(tributylstannyl)-
2-(trimethylsilyl)ethene (9.5 g, 20.4 mmol). The reaction
mixture was stirred at room temperature for 21 h. Et2O (50
mL) and a saturated aqueous solution of potassium fluoride
(20 mL) were added to the mixture, which was vigorously
stirred for 2 h. The resulting precipitate of tributyltin fluoride
was removed by filtration through Celite. The organic layer
was separated, washed with brine, and dried over MgSO4. The
product was purified by column chromatography (silica gel,
hexane) to afford 5 (2.93 g, 60%) as a pale yellow oil: 1H NMR
δ 0.23 (s, 9 H), 1.61 (t, J ) 2.9 Hz, 6 H), 5.62 (d, J ) 0.7 Hz,
1 H), 6.1-6.2 (m, 1 H), 7.2-7.4 (m, 5 H); 13C{1H} NMR δ 0.8,
20.5, 93.8, 97.9, 127.7, 128.0, 128.3, 131.1, 143.7, 152.7, 205.9.
Anal. Calcd for C16H22Si: C, 79.27; H, 9.15. Found: C, 79.18;
H, 9.15.
Vinylallenes (3, 21, 23, and 33) were prepared by the
palladium-catalyzed cross-coupling reactions of the corre-
sponding (organostannyl)alkenes with propargylic bromides
or chlorides according to a procedure analogous to that for 5.
2,5-Dim eth yl-2,3,5-h eptatr ien e (13). A solution of 2-bromo-
2-butene (3 mL, 29.5 mmol) in THF (8 mL) was added dropwise
to a suspension of Mg (0.717 g, 29.5 mmol) in refluxing THF
(20 mL). The reaction mixture was stirred for 1 h and then
cooled to room temperature. Tetrakis(triphenylphosphine)-
palladium(0) (1.00 g, 0.87 mmol) and 3-bromo-3-methyl-1-
butyne (4.34 g, 29.5 mmol) were added successively. The
reaction mixture was stirred for 1 h and poured into a
saturated aqueous solution of NH4Cl (50 mL). The aqueous
phase was extracted with pentane. The combined extracts were
washed with cold water and dried over MgSO4. The pentane
was carefully removed by distillation, and the product was
purified by column chromatography (silica gel, hexane) to
afford 13 (3.1 g, 86%) as an unstable colorless liquid: 1H NMR
δ 1.68 (br s, 3 H), 1.71 (br s, 3 H), 1.74 (d, J ) 2.9 Hz, 6 H),
5.20-5.40 (m, 1 H), 6.00-6.10 (m, 1 H); 13C{1H} NMR δ 13.5,
21.0, 21.6, 90.4, 97.5, 121.9, 131.0, 204.5.
a
b
Isolated yield of 2-alkylidenecyclopent-3-en-1-one. The ratio
of 2-alkylidenecyclopent-3-en-1-one and 2-alkylidenecyclopent-4-
en-1-one was determined by 1H NMR and GC analysis of the
reaction mixture. c 0.5 mol % of [Rh(cod)(dppbe)]OTf was used.
vinylallenes, and their structures were determined.
Vinylallene ligands demonstrated a preference for the
planar structure, presumably maximizing delocalization
of the π-electrons of the endo- and exocyclic double
bonds. The spatial interactions between the substituents
of the vinylallene and phosphine ligands dictate the
coordination modes. Although this steric effect may be
amplified in the present case, since RhCl(PPh3)3 has
sterically demanding phosphine ligands, it is reasonable
to suppose that a similar determinant operates gener-
ally in ligand substitution reactions with vinylallenes.
The present study lends direct evidence to the ring
flipping of a η4 complex via a planar metallacyclopen-
tene complex. The structural findings were rationally
extended to the development of a new synthetic reaction.
The catalytic carbonylative [4 + 1] cycloaddition of
(26) [4 + 2] cycloaddition: (a) Siegel, H.; Hopf, H.; Germer, A.;
Binger, P. Chem. Ber. 1978, 111, 3112. (b) Mandai, T.; Suzuki, S.;
Ikawa, A.; Murakami, T.; Kawada, M.; Tsuji, J . Tetrahedron Lett. 1991,
32, 7687. (c) Murakami, M.; Itami, K.; Ito, Y. J . Am. Chem. Soc. 1997,
119, 7163. (d) Murakami, M.; Ubukata, M.; Itami, K.; Ito, Y. Angew.
Chem., Int. Ed. Engl. 1998, 37, 2248. [4 + 4] cycloaddition: (e)
Murakami, M.; Itami, K.; Ito, Y. Synlett, in press. [4 + 4 + 1]
cycloaddition: (f) Murakami, M.; Itami, K.; Ito, Y. Angew. Chem., Int.
Ed. Engl. 1998, 37, 3418.
(27) Spencer, J . L. Inorg. Synth. 1979, 12, 213.

1334 Organometallics, Vol. 18, No. 7, 1999
Murakami et al.
Vinylallenes (8,28 25, and 31) were prepared by the pal-
ladium-catalyzed cross-coupling reactions of the corresponding
vinylic Grignard reagents with propargylic bromides or chlo-
rides according to a procedure analogous to that for 13.
1-(5,6-Ben zo-1-cycloh exen yl)-3-m et h yl-1,2-b u t a d ien e
(27). To a solution of tetrakis(triphenylphosphine)palladium-
(0) (239 mg, 0.207 mmol) in THF (20 mL) were successively
added (5,6-benzo-1-cyclohexenyl)boronic acid (1.20 g, 6.89
mmol), 1,1-dimethyl-2-propynyl methyl carbonate (1.47 g, 10.3
mmol), K3PO4‚H2O (439 mg, 2.07 mmol), and THF (30 mL).
The mixture was stirred at reflux for 3 h. The cooled reaction
mixture was passed through a short column of Florisil and
eluted with hexane. The filtrate was evaporated, and the
residue was chromatographed on silica gel (hexane) to afford
27 (815 mg, 60%) as a yellow oil: 1H NMR δ 1.91 (d, J ) 3.1
Hz, 6 H), 2.34-2.48 (m, 2 H), 2.86 (t, J ) 7.8 Hz, 2 H), 6.00-
6.10 (m, 1 H), 6.17 (t, J ) 4.8 Hz, 1 H), 7.20-7.40 (m, 3 H),
7.60-7.70 (m, 1 H); 13C{1H} NMR δ 20.6, 23.5, 28.4, 90.4, 96.9,
123.9, 126.1, 126.8, 127.3, 127.5, 132.3, 134.0, 137.0, 203.3.
Vinylallenes (15, 17, 19, and 29) were prepared by the
palladium-catalyzed cross-coupling reactions of the corre-
sponding vinylboronic acids or esters with 1,1-dimethyl-2-
propynyl methyl carbonate according to a procedure analogous
to that for 27.29
Syn th esis of Com p lex 4. To a solution of (E)-4-phenyl-5-
(trimethylsilyl)-1,2,4-pentatriene (3; 25 mg, 0.12 mmol) in
benzene (3 mL) at room temperature was added RhCl(PPh3)3
(129 mg, 0.139 mmol). After the mixture was stirred for 13 h,
the solvent was removed under vacuum. The residue was
subjected to column chromatography (silica gel, CH2Cl2:hexane
) 3:1) to afford 4 (80 mg, 78%) as a yellow powder: 1H NMR
δ 0.07 (s, 9 H), 5.03 (s, 1 H), 6.07 (d, J ) 7.0 Hz, 2 H), 6.67-
6.82 (m, 2 H), 6.92 (t, J ) 7.0 Hz, 1 H), 7.3-7.8 (m, 33 H);
31P{1H} NMR δ 35.1 (d, J Rh-P ) 127.5 Hz); 13C{1H} NMR δ
0.39, 113.8 (d, J Rh-C ) 2.7 Hz), 125.9, 126.0, 127.9, 128.0, 128.1,
128.3, 128.5, 128.7, 129.9, 131.2, 131.6, 132.0, 132.3, 135.0,
135.1, 135.2, 143.2, 153.4 (d, J Rh-C ) 3.0 Hz).
Cr ysta llogr a p h ic An a lysis of 4. Crystal data: C50H48ClP2-
RhSi, Mr ) 877.3, monoclinic, space group P21/a, a ) 23.49(1)
Å, b ) 10.677(4) Å, c ) 19.31(1) Å, â ) 112.55(4)°, U ) 4472-
(4) Å3, Z ) 4, Dc ) 1.30 g/cm3, µ ) 49.04 cm-1. Intensity data
were measured on a Mac Science MXC3 diffractometer using
the ω-2θ scan technique with graphite-monochromated Cu
KR radiation (λ ) 1.541 78 Å). A total of 7137 unique
reflections within 3 e 2θ e 125° were collected. No decay
correction was applied. The data were corrected for Lorentz
and polarization effects. The structure was solved by a direct
method and refined by the full-matrix least-squares procedure
to R ) 0.054 (Rw ) 0.059) for 3981 reflections (I > 2.5σ(I)),
using the Crystan GM package program. The non-hydrogen
atoms were refined anisotropically. Hydrogen atoms on C(6),
C(8), and C(10) were found on a difference Fourier map and
refined isotropically. All other hydrogen atoms were included
in the refinement at calculated distances (0.96 Å) with a
general isotropic temperature factor.
Syn th esis of Com p lexes en d o-6 a n d exo-6. To a solution
of (E)-5-methyl-2-phenyl-1-(trimethylsilyl)-1,3,4-hexatriene (5;
40 mg, 0.165 mmol) in benzene (4 mL) at room temperature
was added RhCl(PPh3)3 (153 mg, 0.165 mmol). After the
mixture was stirred for 20 h, the solvent was removed under
vacuum. The residue was subjected to preparative thin-layer
chromatography (silica gel, CH2Cl2:hexane ) 3:1) to afford
endo-6 (47 mg, 44%, orange powder) and exo-6 (20 mg, 19%,
yellow powder). endo-6: 1H NMR (400 MHz) δ 0.11 (s, 9 H),
1.49 (s, 3 H), 1.59 (s, 3 H), 3.48 (s, 1 H), 4.11 (d, J Rh-H ) 3.0
Hz, 1 H), 6.8-7.7 (m, 20 H); 31P{1H} NMR (C6D6) δ 29.6 (d,
J Rh-P ) 167.6 Hz); 13C{1H} NMR (100 MHz) δ 1.63, 21.51,
25.35, 59.07 (d, J Rh-C ) 3.8 Hz), 116.76, 128.01, 128.11, 128.32,
128.40, 128.52, 128.56, 129.02, 130.01, 130.04, 131.88, 131.91,
132.01, 132.11, 134.15, 134.26, 141.15, 149.14 (d, J P-C ) 28.9
Hz). exo-6: 1H NMR δ -0.05 (s, 9 H), 1.47 (s, 3 H), 1.51 (s, 3
H), 2.26 (d, J Rh-H ) 5.4 Hz, 1 H), 2.81 (s, 1 H), 7.0-7.6 (m, 20
H); 31P{1H} NMR (C6D6) δ 33.8 (d, J Rh-P ) 180.4 Hz); 13C{1H}
NMR δ 0.3, 20.0, 24.1, 59.4 (d, J Rh-C ) 5.2 Hz), 116.7 (d, J Rh-C
) 2.5 Hz), 127.8, 127.9, 128.1, 128.4, 129.1, 130.0 (d, J Rh-C
)
2.4 Hz), 132.3, 133.1, 133.7, 133.8, 134.1, 134.3, 140.0, 145.4
(dd, J Rh-C ) 6.4 Hz, J P-C ) 22.1 Hz).
Cr ystallogr aph ic An alysis of en do-6. Crystal data: C34H37-
ClPRhSi, Mr ) 643.1, monoclinic, space group C2/c, a ) 44.189
Å, b ) 8.242 Å, c ) 17.782 Å, â ) 105.456°, U ) 6242 Å3, Z )
8, Dc ) 1.37 g/cm3, µ ) 7.33 cm-1. Intensity data were collected
on a Mac Science DIP2000 diffractometer with graphite-
monochromated Mo KR radiation (λ ) 0.710 70 Å), using an
imaging plate area detector with an oscillation mode. From a
total of 21 987 observations, 5427 unique reflections were
processed by a MAC-DENZO program. The structure was
solved by a direct method and refined by the full-matrix least-
squares procedure to R ) 0.040 (Rw ) 0.042) for 4217
reflections (I > 2.0σ(I)), using a Crystan GM package program.
The non-hydrogen atoms were refined anisotropically. Hydro-
gen atoms on C(5) and C(7) were found on a difference Fourier
map and refined isotropically. All other hydrogen atoms were
included in the refinement at calculated positions (0.96 Å) with
a general isotropic temperature factor.
Cr ysta llogr a p h ic An a lysis of exo-6. Crystal data: C35H39
-
Cl3PRhSi (exo-6 + CH2Cl2), Mr ) 728.0, triclinic, space group
P1h, a ) 9.809(2) Å, b ) 13.398(3) Å, c ) 14.489(3) Å, R ) 88.75-
(2)°, â ) 78.18(2)°, γ ) 74.50(2)°, U ) 1795.0(6) Å3, Z ) 2, Dc
) 1.19 g/cm3, µ ) 69.59 cm-1. Intensity data were measured
on a Mac Science MXC3 diffractometer using the ω-2θ scan
technique with graphite-monochromated Cu KR radiation (λ
) 1.541 78 Å). A total of 5993 unique reflections within 3 e
2θ e 130° were collected. No decay correction was applied. The
data were corrected for Lorentz and polarization effects. The
structure was solved by a direct method and refined by the
full-matrix least-squares procedure to R ) 0.062 (Rw ) 0.068)
for 5348 reflections (I > 3.0σ(I)), using the Crystan GM
package program. The crystal contains one molecule of exo-6
and one molecule of CH2Cl2 in an asymmetric unit. The non-
hydrogen atoms, except those of CH2Cl2, were refined aniso-
tropically. Hydrogen atoms on C(5) and C(7) were found on a
difference Fourier map and refined isotropically. All other
hydrogen atoms were included in the refinement at calculated
distances (0.96 Å) with isotropic temperature factors.
Syn th esis of Com p lex 9. To a solution of 5-methyl-2-
phenyl-1,3,4-hexatriene (8; 430 mg, 2.53 mmol) in benzene (20
mL) at room temperature was added RhCl(PPh3)3 (2.00 g, 2.16
mmol). After the mixture was stirred for 24 h, the solvent was
removed under vacuum. Addition of ether to the residue
afforded 9 (1.65 g, 92%) as an orange powder. As frequently
observed with five-coordinate complexes,30 9 became stereo-
chemically nonrigid in solution to present complicated NMR
spectra. The data for the predominant isomer, which are
consistent with the planar crystal structure, are given below:
1H NMR (C6D6, 400 MHz) δ 1.41 (s, 3 H), 1.66 (s, 3 H), 4.25-
4.33 (br, 2 H), 5.35 (s, 1 H), 6.80-8.10 (m, 35 H); 13C{1H} NMR
(C6D6, 100 MHz) δ 19.6, 25.7, 31.1 (d, J Rh-C ) 32.8 Hz), 120-
145 (m); 31P{1H} NMR (C6D6, 121 MHz) δ 26.5 (d, J Rh-P ) 126.2
Hz). Anal. Calcd for C49H44ClP2Rh: C, 70.64; H, 5.32. Found:
C, 70.91; H, 5.48.
Cr ysta llogr a p h ic An a lysis of 9. Crystal data: C50H48
-
ClOP2Rh (9 + MeOH), Mr ) 865.2, orthorhombic, space group
P212121, a ) 19.33(1) Å, b ) 21.74(1) Å, c ) 10.13(1) Å, U )
4259.9(4) Å3, Z ) 4, Dc ) 1.349 g/cm3, µ ) 48.90 cm-1. Intensity
data were measured on a Mac Science MXC3 diffractometer
using the ω-2θ scan technique with graphite-monochromated
Cu KR radiation (λ ) 1.541 78 Å). A total of 3918 unique
(28) Pasto, D. J .; Kong, W. J . Org. Chem. 1989, 54, 4028.
(29) Moriya, T.; Miyaura, N.; Suzuki, A. Synlett 1994, 149.
(30) Muetterties, E. L. Acc. Chem. Res. 1970, 3, 266.

Coordination and Cycloaddition of Vinylallenes
Organometallics, Vol. 18, No. 7, 1999 1335
reflections within 3 e 2θ e 130° were collected. No decay
correction was applied. The data were corrected for Lorentz
and polarization effects. The structure was solved by a direct
method and refined by the full-matrix least-squares procedure
to R ) 0.063 (Rw ) 0.067) for 3616 reflections (I > 3.0σ(I)),
using the Crystan GM package program. The crystal contains
one molecule of 9 and one molecule of MeOH in an asymmetric
unit. The non-hydrogen atoms, except those of MeOH, were
refined anisotropically. Hydrogen atoms were included in the
refinement at calculated distances (0.96 Å) with isotropic
temperature factors calculated from those of the bonded atoms.
Syn th esis of Com p lex 10. To a solution of Pt(cod)2 (200
mg, 486 µmol) in CH2Cl2 (15 mL) at room temperature was
added 5-methyl-2-phenyl-1,3,4-hexatriene (8; 91 mg, 535
µmol). After the mixture was stirred for 30 min, dppe (194 mg,
486 µmol) was added. The mixture was stirred for an ad-
ditional 30 min, and then the solvent was removed under
vacuum. The residue was dissolved in a small quantity of CH2-
Cl2, and the resulting solution was added to a stirred solution
of hexane to afford the title complex 10 (357 mg, 87%, beige
powder) as a CH2Cl2 solvate. The solvating CH2Cl2 was
gradually lost under vacuum: 1H NMR δ 1.59 (s and satellite,
J Pt-H ) 10.3 Hz, 3 H), 1.90-2.40 (m, 4 H), 2.00 (s and satellite,
J Pt-H ) 9.5 Hz, 3 H), 2.84 (dd, J P-H ) 9.3, 8.3 Hz and satellite,
J Pt-H ) 74.5 Hz, 2 H), 6.97-7.58 (m, 18 H), 7.62-7.76 (m, 4
H), 7.92-8.10 (m, 4 H); 31P{1H} NMR (121 MHz) δ 45.3 (d,
J P-P ) 3 Hz and satellite, J Pt-P ) 1818 Hz), 50.4 (d, J P-P ) 3
Hz and satellite, J Pt-P ) 1842 Hz); selected 13C{1H} NMR
resonances (75 MHz) δ 20.1 (d, J P-C ) 8 Hz and satellite, J Pt-C
) 50 Hz), 28.1 (m), 31.5 (dd, J P-C ) 89, 5 Hz and satellite,
J Pt-C ) 603 Hz), 33.6 (m), 34.8 (dd, J P-C ) 7, 5 Hz and satellite,
J Pt-C ) 52 Hz), 159.0 (dd, J P-C ) 113, 6 Hz and satellite, J Pt-C
) 926 Hz); HRMS m/e calcd for C39H38P2Pt 763.2096, found
763.2099. Anal. Calcd (partially solvated formula C39H38P2Pt‚
0.8CH2Cl2): C, 57.47; H, 4.80. Found: C, 57.76; H, 4.90.
P r ep a r a tion of [Rh (d p p be)(cod )]OTf. To a solution of
[Rh(cod)2]OTf (144 mg, 0.307 mmol) in CH2Cl2 (5 mL) at room
temperature was added dropwise a solution of dppbe (146 mg,
0.326 mmol) in CH2Cl2 (4 mL). The reaction mixture was
stirred for 30 min and then concentrated to ca. 1 mL under
vacuum. Et2O (15 mL) was added, and the resulting precipi-
tates were washed with Et2O to afford [Rh(dppbe)(cod)]OTf
(239 mg, 97%) as orange solids: 1H NMR δ 2.24-2.60 (m, 8
H), 5.08 (br s, 4 H), 7.40-7.70 (m, 24 H); 31P{1H} NMR (121
MHz) δ 58.2 (d, J Rh-P ) 149 Hz).
Syn th esis of 4,5-Dim eth yl-2-isop r op ylid en e-3-cyclo-
p en ten on e (14) by th e Rh od iu m -Ca ta lyzed [4 + 1] Cy-
cloa d d ition . A mixture of [Rh(cod)(dppbe)]OTf (16.5 mg, 20.5
µmol) and 13 (50.0 mg, 409 µmol) in DME (2 mL) under 10
atm of CO in an autoclave was stirred in an oil bath at 60 °C
for 15 h. After the mixture was cooled, the solvent was removed
under vacuum. The residue was subjected to preparative thin-
layer chromatography (silica gel, ether:hexane ) 1:7) to afford
14 (52.2 mg, 85%): 1H NMR δ 1.14 (d, J ) 7.6 Hz, 3 H), 1.87
(s, 3 H), 1.90 (s, 3 H), 2.21 (s, 3 H), 2.67 (q, J ) 7.6 Hz, 1 H),
6.41 (s, 1 H); 13C{1H} NMR δ 13.8, 15.9, 20.0, 23.4, 50.4, 126.4,
133.1, 140.2, 142.4, 208.9; HRMS m/e calcd for C10H14
O
150.1045, found 150.1053.
2,3-D im e t h y l-5-is o p r o p y lid e n e -2-c y c lo p e n t e n o n e
(14′): 1H NMR δ 1.71 (s, 3 H), 1.85 (s, 3 H), 2.02 (s, 3 H), 2.29
(s, 3 H), 2.96 (s, 2 H); 13C{1H} NMR δ 8.2, 16.3, 19.6, 23.9,
37.4, 128.9, 139.3, 143.8, 159.1, 197.1; MS m/e 150 (M+). Anal.
Calcd for C10H14O: C, 79.96; H, 9.39. Found: C, 80.12; H, 9.11.
The rhodium-catalyzed [4 + 1] cycloaddition reactions for
the synthesis of the following compounds were carried out
according to the preceding procedure for 14 under conditions
specified in Table 7. Compound numbers with
designate 2-alkylidene-4-cyclopentenone forms.
a prime
4,5-D ip r o p y l-2-is o p r o p y lid e n e -3-c y c lo p e n t e n o n e
(16): 1H NMR δ 0.86 (t, J ) 7.1 Hz, 3 H), 0.96 (t, J ) 7.3 Hz,
3 H), 1.05-1.40 (m, 2 H), 1.40-1.65 (m, 3 H), 1.70-1.90 (m, 1
H), 1.91 (s, 3 H), 2.10-2.25 (m, 2 H), 2.22 (s, 3 H), 2.76 (t, J )
4.4 Hz, 1 H), 6.46 (d, J ) 1.4 Hz, 1 H); 13C{1H} NMR δ 15.3,
15.6, 19.9, 21.2, 21.6, 24.6, 32.0, 33.5, 55.1, 127.4, 134.8, 141.1,
146.3, 210.2; HRMS m/e calcd for C14H22O 206.1670, found
206.1655.
2,3-D ip r o p y l-5-is o p r o p y lid e n e -2-c y c lo p e n t e n o n e
(16′): 1H NMR δ 0.90 (t, J ) 7.4 Hz, 3 H), 0.96 (t, J ) 7.3 Hz,
3 H), 1.20-1.70 (m, 4 H), 1.87 (s, 3 H), 2.20 (t, J ) 7.7 Hz, 2
H), 2.31 (s, 3 H), 2.40 (t, J ) 7.6 Hz, 2 H), 2.99 (s, 2 H); 13C-
{1H} NMR δ 14.5, 19.9, 21.4, 22.2, 24.2, 25.7, 30.0, 32.6, 35.1,
Cr ysta llogr a p h ic An a lysis of 10. Crystal data: C40H40
-
Cl2P2Pt (10 + CH2Cl2), Mr ) 848.7, monoclinic, space group
P21/c, a ) 12.2706(9) Å, b ) 13.9824(7) Å, c ) 21.241(2) Å, â
) 104.920(3)°, U ) 3521.5 Å3, Z ) 4, Dc ) 1.601 g/cm3, µ )
42.39 cm-1. Intensity data were collected on a Rigaku RAXIS-
IV diffractometer with graphite-monochromated Mo KR radia-
tion (λ ) 0.710 70 Å), using an imaging plate area detector
with an oscillation mode. A total of 7395 unique reflections
were collected. The data were corrected for Lorentz and
polarization effects. The structure was solved by a direct
method and refined by the full-matrix least-squares procedure
to R ) 0.061 (Rw ) 0.079) for 5504 reflections (I > 3.0σ(I)),
using the teXsan package program. The crystal contains one
molecule of 10 and one molecule of CH2Cl2 in an asymmetric
unit. The non-hydrogen atoms, except those of CH2Cl2, were
refined anisotropically. Hydrogen atoms were included in the
refinement at calculated positions (0.95 Å) with isotropic
temperature factors.
Rea ction of Com p lex 9 w ith Ca r bon Mon oxid e. A
solution of 9 (105 mg, 126 µmol) in CH2Cl2 (3 mL) under an
atmosphere of carbon monoxide (1 atm) was stirred at room
temperature for 18 h. The solvent was removed under vacuum.
The residue was subjected to preparative thin-layer chroma-
tography (ether:hexane ) 1:7) to afford 12′ (24 mg, 96%) as a
white powder: 1H NMR δ 2.06 (s, 3 H), 2.32 (s, 3 H), 3.30 (d,
J ) 1.7 Hz, 2 H), 7.20-7.50 (m, 6 H); 13C{1H} NMR δ 20.5,
23.8, 44.0, 125.2, 126.7, 128.2, 128.7, 134.8, 135.2, 137.1, 144.0,
204.6; HRMS m/e calcd for C14H14O 198.1045, found 198.1049.
The reactions of complexes endo-6 and exo-6 with carbon
monoxide, affording 11, were carried out according to the
preceding procedure for complex 9. 11: 1H NMR δ -0.06 (s, 9
H), 2.03 (s, 3 H), 2.28 (s, 3 H), 3.44 (s, 1 H), 6.91 (s, 1 H), 7.25-
7.60 (m, 5 H); 13C{1H} NMR δ -2.0, 20.5, 23.9, 51.7, 123.1,
126.0, 127.8, 128.4, 136.0, 136.5, 141.0, 143.0, 206.0; MS m/e
270 (M+). Anal. Calcd for C17H22OSi: C, 75.50; H, 8.20.
Found: C, 75.38; H, 8.20.
129.3, 143.8, 144.2, 163.5, 197.5; HRMS m/e calcd for C14H22
O
206.1670, found 206.1668.
4,5-Dib u t yl-2-isop r op ylid en e-3-cyclop en t en on e (18).
1H NMR δ 0.85 (t, J ) 7.3 Hz, 3 H), 0.93 (t, J ) 6.7 Hz, 3 H),
1.00-1.85 (m, 10 H), 1.91 (s, 3 H), 2.10-2.30 (m, 2 H), 2.22 (s,
3 H), 2.77 (t, J ) 4.4 Hz, 1 H), 6.46 (d, J ) 1.5 Hz, 1 H); 13C-
{1H} NMR δ 14.15, 14.21, 20.2, 22.8, 23.3, 23.6, 27.6, 28.4,
29.5, 30.1, 54.1, 126.3, 133.9, 140.1, 145.5, 209.2; HRMS m/e
calcd for C16H26O 234.1982, found 234.1981.
2,3-Dib u t yl-5-isop r op ylid en e-2-cyclop en t en on e (18′):
1H NMR δ 0.85-1.00 (m, 6 H), 1.20-1.60 (m, 8 H), 1.87 (s, 3
H), 2.15-2.30 (m, 2 H), 2.31 (s, 3 H), 2.35-2.48 (m, 2 H), 2.98
(s, 2 H); HRMS m/e calcd for
C16H26O 234.1982, found
234.1980.
4,5-Diet h yl-2-(1-et h ylp r op ylid en e)-3-cyclop en t en on e
(20): 1H NMR δ 0.72 (t, J ) 7.5 Hz, 3 H), 1.02 (t, J ) 7.5 Hz,
3 H), 1.07 (t, J ) 7.6 Hz, 3 H), 1.13 (t, J ) 7.4 Hz, 3 H), 1.54-
1.73 (m, 1 H), 1.78-1.96 (m, 1 H), 2.10-2.40 (m, 4 H), 2.55-
2.83 (m, 3 H), 6.48 (d, J ) 1.6 Hz, 1 H); 13C{1H} NMR δ 9.5,
11.6, 12.9, 13.3, 21.5, 23.3, 24.1, 27.8, 55.0, 125.5, 132.8, 146.8,
151.8, 209.1; HRMS m/e calcd for C14H22O 206.1670, found
206.1667.
2,3-Diet h yl-5-(1-et h ylp r op ylid en e)-2-cyclop en t en on e
(20′): 1H NMR δ 1.00 (t, J ) 7.6 Hz, 3 H), 1.07 (t, J ) 7.5 Hz,
3 H), 1.08 (t, J ) 7.6 Hz, 3 H), 1.14 (t, J ) 7.7 Hz, 3 H), 2.19

1336 Organometallics, Vol. 18, No. 7, 1999
Murakami et al.
(q, J ) 7.6 Hz, 2 H), 2.23 (q, J ) 7.5 Hz, 2 H), 2.44 (q, J ) 7.7
Hz, 2 H), 2.81 (q, J ) 7.6 Hz, 2 H), 3.00 (s, 2 H); 13C{1H} NMR
δ 12.3, 12.6, 13.2, 13.6, 16.7, 23.3, 23.5, 28.3, 33.9, 128.0, 144.5,
155.5, 164.3, 197.0.
4,5-D ip h e n y l-2-is o p r o p y lid e n e -3-c y c lo p e n t e n o n e
(22): 1H NMR δ 2.12 (s, 3 H), 2.28 (s, 3 H), 4.46 (d, J ) 1.3
Hz, 1 H), 7.20-7.40 (m, 8 H), 7.40-7.50 (m, 2 H), 7.51 (d, J )
1.3 Hz, 1 H); 13C{1H} NMR δ 21.2, 24.5, 60.0, 126.6, 127.6,
128.4, 128.5, 128.9, 129.1, 129.3, 133.5, 134.9, 137.6, 140.1,
146.3, 203.8; HRMS m/e calcd for C20H18O 274.1357, found
274.1363.
4-(E t h oxyca r b on yl)-2-isop r op ylid en e-5-p h en yl-3-cy-
clop en ten on e (24): 1H NMR δ 1.16 (d, J ) 7.1 Hz, 3 H), 2.15
(s, 3 H), 2.32 (s, 3 H), 4.06-4.22 (m, 2 H), 4.28 (d, J ) 1.6 Hz,
1 H), 7.10-7.20 (m, 2 H), 7.20-7.40 (m, 3 H), 7.90 (d, J ) 1.6
Hz, 1 H); 13C{1H} NMR δ 14.3, 21.3, 24.6, 58.4, 60.7, 127.3,
127.8, 128.8, 132.7, 132.8, 137.2, 141.5, 154.8, 164.6, 202.5;
HRMS m/e calcd for C17H18O3 270.1255, found 270.1252.
8-Isop r op ylid en ebicyclo[4.3.0]n on -1(9)-en -7-on e (26):
1H NMR δ 0.80-1.50 (m, 4 H), 1.80-2.40 (m, 3 H), 1.92 (s, 3
H), 2.22 (s, 3 H), 2.45-2.70 (m, 2 H), 6.36 (s, 1 H); 13C{1H}
NMR δ 20.0, 23.5, 25.3, 27.3, 28.9, 29.8, 52.8, 122.6, 133.4,
140.6, 145.0, 208.3; MS m/e 176 (M+). Anal. Calcd for
9-Isop r op ylid en ebicyclo[5.3.0]d ec-1(7)-en -9-on e (30′):
1H NMR δ 1.45-1.70 (m, 4 H), 1.70-1.90 (m, 2 H), 1.86 (s, 3
H), 2.25-2.40 (m, 2 H), 2.30 (s, 3 H), 2.40-2.55 (m, 2 H), 3.00
(s, 2 H); 13C{1H} NMR δ 19.7, 23.9, 24.1, 26.8, 27.0, 31.5, 33.1,
37.6, 129.5, 144.2, 145.4, 166.1, 196.4; HRMS m/e calcd for
C
13H18O 190.1358, found 190.1338.
(E)-2-Bu tylid en e-4,5-d im eth yl-3-cyclop en ten on e (32):
1H NMR δ 0.93 (t, J ) 7.3 Hz, 3 H), 1.18 (d, J ) 7.6 Hz, 3 H),
1.40-1.58 (m, 2 H), 1.93 (s, 3 H), 2.21 (q, J ) 7.9 Hz, 2 H),
2.74 (q, J ) 7.6 Hz, 1 H), 6.11 (t, J ) 7.9 Hz, 1 H), 6.45 (s, 1
H); 13C{1H} NMR δ 13.6, 13.9, 16.2, 22.3, 31.2, 49.4, 124.7,
129.1, 138.3, 146.8, 208.0. Anal. Calcd for C11H16O: C, 80.44;
H, 9.82. Found: C, 80.17; H, 10.02.
(E )-2-B u t y lid e n e -4,5-d im e t h y l-4-c y c lo p e n t e n o n e
(32′): 1H NMR δ 0.92 (t, J ) 7.3 Hz, 3 H), 1.49 (sextet, J )
7.3 Hz, 2 H), 1.75 (s, 3 H), 2.06 (s, 3 H), 2.10-2.21 (m, 2 H),
2.99 (s, 2 H), 6.52 (t, J ) 7.6 Hz, 1 H); 13C{1H} NMR δ 8.3,
13.9, 16.7, 21.9, 31.6, 35.2, 133.2, 134.9, 138.3, 162.3, 196.5.
Anal. Calcd for C11H16O: C, 80.44; H, 9.82. Found: C, 80.20;
H, 10.03.
(E)-4-(Eth oxyca r bon yl)-2-eth ylid en e-5-p h en yl-3-cyclo-
p en ten on e (E-34): 1H NMR (300 MHz) δ 1.16 (t, J ) 7.2 Hz,
3 H), 2.08 (d, J ) 7.5 Hz, 3 H), 4.06-4.22 (m, 2 H), 4.34 (d, J
) 1.5 Hz, 1 H), 6.71 (q, J ) 7.5 Hz, 1 H), 7.10-7.40 (m, 5 H),
7.89 (s, 1 H); 13C{1H} NMR (75 MHz) δ 13.9, 15.6, 57.3, 60.7,
127.3, 127.7, 128.7, 136.2, 136.6, 136.8, 138.4, 164.1, 201.2;
HRMS m/e calcd for C16H16O3 256.1098, found 256.1099.
C
12H16O: C, 81.77; H, 9.15. Found: C, 81.92; H, 9.38.
8-I s o p r o p y li d e n e b i c y c lo [4.3.0]n o n -1(6)-e n -7-o n e
(26′): 1H NMR δ 1.60-1.80 (m, 4 H), 1.84 (s, 3 H), 2.10-2.25
(m, 2 H), 2.25-2.50 (m, 2 H), 2.29 (s, 3 H), 2.95 (s, 2 H); 13C-
{1H} NMR δ 19.5, 20.2, 21.8, 22.3, 23.9, 27.6, 35.9, 129.3, 141.9,
143.8, 162.8, 196.5. Anal. Calcd for C12H16O: C, 81.77; H, 9.15.
Found: C, 81.85; H, 9.36.
Syn t h esis of 24 by t h e P la t in u m -Ca t a lyzed [4 + 1]
Cycloa d d ition . A mixture of Pt(cod)2 (3.4 mg, 8.3 µmol),
dppbe (4.4 mg, 9.9 µmol), and 23 (40.0 mg, 165 µmol) in DME
(2 mL) under 10 atm of CO in an autoclave was stirred in an
oil bath at 60 °C for 14 h. After the mixture was cooled, the
solvent was removed under vacuum. The residue was subjected
to preparative thin-layer chromatography (silica gel, ether:
hexane ) 1:3) to afford 24 (40.6 mg, 91%).
2,3-Ben zo-8-isop r op ylid en ebicyclo[4.3.0]n on -1(9)-en -7-
on e (28): 1H NMR δ 1.45-1.70 (m, 1 H), 2.05 (s, 3 H), 2.31
(s, 3 H), 2.40-2.53 (m, 1 H), 2.90-3.14 (m, 3 H), 7.00 (d, J )
2.3 Hz, 1 H), 7.12-7.28 (m, 3 H), 7.60-7.70 (m, 1 H); 13C{1H}
NMR δ 20.5, 23.8, 24.3, 30.0, 51.5, 122.1, 123.9, 126.4, 128.1,
129.4, 131.4, 134.6, 137.2, 139.0, 143.2, 206.9; HRMS m/e calcd
for C16H16O 224.1201, found 224.1199.
4,5-Ben zo-8-isop r op ylid en ebicyclo[4.3.0]n on -1(6)-en -7-
on e (28′): 1H NMR δ 1.97 (s, 3 H), 2.38 (s, 2 H), 2.47-2.62
(m, 2 H), 2.93 (t, J ) 8.2 Hz, 2 H), 3.38 (s, 2 H), 7.20-7.45 (m,
4 H); 13C{1H} NMR δ 18.4, 20.0, 24.3, 28.1, 31.0, 124.2, 126.9,
128.4, 130.0, 130.3, 131.9, 138.7, 141.5, 145.6, 156.1, 195.5;
HRMS m/e calcd for C16H16O 224.1201, found 224.1184.
9-I s o p r o p y lid e n e b ic y c lo [5.3.0]d e c -1(10)-e n -9-o n e
(30): 1H NMR δ 1.40-1.55 (m, 3 H), 1.55-1.85 (m, 4 H), 1.91
(s, 3 H), 1.90-2.20 (m, 1 H), 2.21 (s, 3 H), 2.45-2.60 (m, 2 H),
2.75-2.90 (m, 1 H), 6.40-6.50 (m, 1 H); 13C{1H} NMR δ 20.1,
23.4, 28.0, 28.6, 30.2, 30.9, 31.7, 56.3, 126.0, 133.7, 139.8, 147.4,
208.5; HRMS m/e calcd for C13H18O 190.1358, found 190.1366.
Ack n ow led gm en t. We thank Prof. K. Tamao and
Dr. S. Yamaguchi (Kyoto University) for collecting the
diffraction data for 10. K.I. thanks the J apan Society
for the Promotion of Science for a predoctoral fellowship.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, anisotropic thermal parameters, and bond lengths
and bond angles for 4, endo-6, exo-6, 9, and 10. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM990028N