[3 + 2] Annulation of Allylidenetriphenylphosphorane with 1,2-Diacylethylenes and 1,2-Diacylacetylenes: A One-Step Synthesis of Tri- and Tetrasubstituted Cyclopentadienes and Fulvenes

Article abstract of DOI:10.1021/jo970594x

Allylidenetriphenylphosphoranes underwent [3 + 2] annulation with 1,2-diacylethylenes at room temperature to give cyclopentadienes 11-17 having various substituents except for (Z)-3-acetylacrolein (18) which gave cyclohexadiene 19 derived from [3 + 3] ann

Full text of DOI:10.1021/jo970594x

J . Org. Chem. 1997, 62, 6529-6538
6529
[3 + 2] An n u la tion of Allylid en etr ip h en ylp h osp h or a n e w ith
1,2-Dia cyleth ylen es a n d 1,2-Dia cyla cetylen es: A On e-Step
Syn th esis of Tr i- a n d Tetr a su bstitu ted Cyclop en ta d ien es a n d
F u lven es
Yuichiro Himeda,† Hiroshi Yamataka,‡ Ikuo Ueda,‡ and Minoru Hatanaka*,§
Department of Molecular Engineering, National Institute of Materials and Chemical Research, Higashi
1-1, Tsukuba, Ibaraki 305, J apan, The Institute of Scientific and Industrial Research, Osaka University,
Mihogaoka, Ibaraki, Osaka 567, J apan, and Department of Applied Chemistry and Biotechnology,
Faculty of Engineering, Fukui University, Bunkyo, Fukui 910, J apan
Received April 1, 1997X
Allylidenetriphenylphosphoranes underwent [3 + 2] annulation with 1,2-diacylethylenes at room
temperature to give cyclopentadienes 11-17 having various substituents except for (Z)-3-
acetylacrolein (18) which gave cyclohexadiene 19 derived from [3 + 3] annulation as the sole
annulation product. The resulting cyclopentadienes were mixtures of the corresponding double-
bond isomers which arose through an equilibrium process from the initially formed 1,3-dienes a
under the weakly basic reaction conditions. Similar reactions of the phosphoranes with 1,2-
diacylacetylenes afforded substituted fulvenes 24, 25, and 28 directly without the attendant
formation of the corresponding benzene derivatives which come from another possible [3 + 3]
annulation. The observed high level of the preference for the [3 + 2] annulation is discussed on
the basis of the semiempirical PM3 MO calculations. The calculations suggested that the course
of the annulation may be kinetically controlled at the oxaphosphetane-forming step of the
intramolecular Wittig reaction.
In tr od u ction
tion1 or condensation with aldehydes and ketones.4
Application of these approaches to substituted cyclopen-
tadienes is usually unsuccessful and leads to the forma-
tion of regioisomeric mixtures, although this route is
often used for the preparation of the 1,3-substituted
derivatives with relatively hindered substituents.5 Sev-
eral interesting methods for the direct preparation of di-,
tri-, or tetrasubstituted cyclopentadienes include acid-
catalyzed cyclization of 1,4-pentadien-3-ol,6 palladium-
mediated cyclization of 1,5-hexadien-3-ol,7 rearrangement
of vinylcyclopropylidene,8 and cycloaddition of R,â-
unsaturated Fisher carbene complexes to alkyne or
alkene.9,10 On the other hand, there are few precedents
for the preparation of substituted fulvenes in a regiose-
lective manner.4a,11
Considerable attention has been focused on the syn-
thesis of substituted cyclopentadienes, since they serve
as a useful construction unit of fused ring systems via
an inter- and intramolecular Diels-Alder reaction1 in
addition to their increasing usefulness as ligands of
various transition metals.2 Fulvenes are also known to
undergo several types of inter- or intramolecular cycload-
ditions, including [6 + 2], [6 + 4], and [4 + 2] cycliza-
tions,3 which may provide powerful tools for the con-
struction of various ring systems. However, the utility
of these cyclizations is limited due to the general inac-
cessibility of the substituted cyclopentadienes and ful-
venes. Alkylcyclopentadienes or fulvenes are readily
derived from cyclopentadiene by base-catalyzed alkyla-
(4) (a) For an exellent review, see: Zeller, K.-P. Pentafulvenes. In
Methoden der Organischen Chemie; Georg Thieme Verlag: Stuttgart,
1985; Vol. 5/2C, pp 504-684. (b) Buchi, G.; Berthet, D.; Decorzant,
R.; Grieder, A.; Hauser, A. J . Org. Chem. 1976, 41, 3208-3209. (c)
Stone, K. J .; Little, R. D. J . Org. Chem. 1984, 49, 1849-1853. (d)
J acobs, S. J .; Schulz, S. A.; J avin, R.; Novak, J .; Dougherty, D. A. J .
Am. Chem. Soc. 1993, 115, 1744-1753. (e) Erden, I.; Xu, F.-P.; Sadoun,
A.; Smith, W.; Sheff, G.; Ossun. M. J . Org. Chem. 1995, 60, 813-820
and references cited therein.
(5) (a) Alder, K.; Ache, H.-J . Chem. Ber. 1962, 95, 503-510. (b)
McLean, S.; Hayes, P. Tetrahedron 1965, 21, 2313-2327. (c) Berg-
mann, E. D. Chem. Rev. 1968, 68, 41-84. (d) Hafner, K.; Thiele, G.
F.; Mink, C. Angew. Chem., Int. Ed. Engl. 1988, 27, 1191-1192. (e)
J utzi, P.; Dahlhaus, J . Synthesis 1993, 684-686.
(6) (a) Threlkel, R. S.; Bercaw, J . E. J . Organomet. Chem. 1977, 136,
1-5. (b) Wochner, F.; Zsolnai, L.; Huttner, G.; Brintzinger, H. H. J .
Organomet. Chem. 1985, 288, 69-77. (c) Stein, D.; Sitzmann, H. J .
Organomet. Chem. 1991, 402, C1-C3. (d) Garner, C. M.; Prince, M. E.
Tetrahedron Lett. 1994, 35, 2463-2464.
(7) Zair, T.; Santelli-Rouvier, C.; Santelli, M. Tetrahedron 1993, 49,
3313-3324.
(8) (a) Scattebol, L. Chem. Ind. 1962, 2146-2147; Tetrahedron 1967,
23, 1107-1117. (b) Holm, K. H.; Scattebol, L. Acta Chem. Scand. Ser.
B 1985, 39, 549-561. (d) Paquette, L. A.; Gugelchuk, M.; McLaughlin
M. L. J . Org. Chem. 1987, 52, 4932-4940. (c) Baird, M. S.; J efferies,
I. Tetrahedron Lett. 1986, 27, 2493-2496.
(9) (a) Aumann, R.; Heinen, H.; Dartmann, M.; Krebs, B. Chem. Ber.
1991, 124, 2343-2347. (b) Flynn, B. L.; Funke, F. J .; Silveira, C. C.;
de Meijere, A. Synlett 1995, 1007-1010. (c) Aumann, R.; Meyer, A.
G.; Frohlich, R. Organometallics 1996, 15, 5018-5027.
† National Institute of Materials and Chemical Research.
‡ Osaka University.
§ Fukui University.
X Abstract published in Advance ACS Abstracts, August 15, 1997.
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1994, 35, 6627-6630.
S0022-3263(97)00594-X CCC: $14.00 © 1997 American Chemical Society

6530 J . Org. Chem., Vol. 62, No. 19, 1997
Himeda et al.
Sch em e 1
Sch em e 2
Sch em e 3
We recently demonstrated that allylidenetriphenylphos-
phorane undergoes a [3 + 2] annulation with R-halo
ketones to give polysubstituted cyclopentadienes in a
regioselective manner (Scheme 1).12 The occurrence of
this annulation reveals that allylidenephosphorane acts
as a bifunctional reagent, first nucleophilic substitution
at the γ-position of the phosphorane followed by an
intramolecular Wittig reaction.13 A similar [3 + 3]
annulation of the phosphorane with R,â-unsaturated
aldehydes and ketones has been reported to form cyclo-
hexadienes in moderate yields.14,15 In this context, we
were interested in the reaction of allylidenetriphenylphos-
phorane with 1,2-diacylethylenes, in which there are two
possible pathways for the annulation, leading to the
formation of either cyclohexadiene or cyclopentadiene
(Scheme 2). Although it was not clear which cyclization
would complete effectively, we expected predominance for
the [3 + 2] annulation because the cyclopentadiene
formation with R-halo ketone proceeds more efficiently
than the previous cyclohexadiene synthesis with R,â-
unsaturated ketones. Similarly, 1,2-diacylacetylene could
serve as a substrate for the annulation with the phos-
phorane (Scheme 3). However, phosphoranes including
allylidenetriphenylphosphorane usually do not undergo
Michael addition to acetylenes bearing electron-with-
drawing groups and ylide interchange occurs via the
phosphacyclobutene intermediate.16 Accordingly, of par-
ticular interest is whether diacylacetylenes could take
part as the Michael acceptor of allylidenephosphorane
and furthermore whether a subsequent intramolecular
Wittig reaction would prefer the [3 + 2] annulation to
the [3 + 3] congener, in which the former would lead to
fulvene formation with internal strain and the latter to
the formation of stable benzenoids.
Here, we report in detail that allylidenetriphenyl-
phoshorane effects the [3 + 2] annulation with both 1,2-
diacylacetylenes and 1,2-diacylethylenes and provides
efficient methods for the regioselective preparation of the
substituted cyclopentadienes and fulvenes in a one-step
fashion.17
Resu lts a n d Discu ssion
Cyclop en ta d ien e Syn th esis. Stabilized allylidene-
phosphoranes, (3-(ethoxycarbonyl)-2-substituted prop-2-
enylidene)triphenylphosphoranes 4-6, were used as
starting phosphoranes. Since the phosphoranes can be
generated in situ from the corresponding phosphonium
salts in the presence of a weak base such as NaHCO3,
allylphosphonium salts 1-3, in which 1 and 3 are in a
(10) For other interesting cyclization, see: (a) Feitler, D.; Whitesides,
G. M. Inorg. Chem. 1976, 15, 466-469. (b) Sekiya, A.; Stille, J . K. J .
Am. Chem. Soc. 1981, 103, 5096-5100. (c) Koschinsky, R.; Kohli, T.-
P.; Mayr, H. Tetrahedron Lett. 1988, 29, 5641-5644. (d) Lee, B. Y.;
Moon, H.; Chung Y. K. J . Am. Chem. Soc. 1994, 116, 2163-2164. (e)
Takahashi, T.; Xi, Z.; Kotora, M.; Xi, C. Tetrahedron Lett. 1996, 37,
7521-7524.
(11) (a) Lee, G. C. M.; Tobias, B.; Holmes, J . M.; Harcourt, D. A.;
Garst, M. E. J . Am. Chem. Soc. 1990, 112, 9330-9336. (b) Silverberg,
L. J .; Wu, G.; Rheingold, A. L.; Heck, R. F. J . Organomet. Chem. 1991,
409, 411-420.
(12) (a) Hatanaka, M.; Himeda, Y.; Ueda, I. J . Chem. Soc., Perkin.
Trans. 1 1993, 2269-2274. (b) Hatanaka, M.; Himeda, Y.; Imashiro,
R.; Tanaka, Y.; Ueda, I. J . Org. Chem. 1994, 59, 111-119.
(13) (a) Bestmann, H. J . Angew. Chem., Int. Ed. Engl. 1965, 4, 583,
645, 830. (b) Corey, E. J .; Erickson, B. W. J . Org. Chem. 1974, 39,
821-825. (c) Bestmann, H. J .; Roth, K. Angew. Chem., Int. Ed. Engl.
1981, 20, 575-576.
(14) (a) Bu¨chi, G.; Wu¨est, H. Helv. Chim. Acta. 1971, 54, 1767-
1776. (b) Bohlmann, F.; Zdero, C. Chem. Ber. 1973, 106, 3779-3787.
(c) Dauben, W. G.; Ipaktschi, J . J . Am. Chem. Soc. 1973, 95, 5088-
5089. (d) Dauben, W. G.; Hart, D. J .; Ipaktschi, J .; Kozikowski, A. P.
Tetrahedron Lett. 1973, 4425-4428. (e) Dauben, W. G.; Kozikowski,
A. P. Tetrahedron Lett. 1973, 3711-3714. (f) Neff, J . R.; Gruetzmacher,
R. R.; Nordlander, J . E. J . Org. Chem. 1974, 39, 3814-3819. (g) Vedejs,
E.; Bershas, J . P. Tetrahedron Lett. 1975, 1359-1362. (h) Martin, S.
F.; Desai, S. R. J . Org. Chem. 1977, 42, 1664-1666. (i) Hatanaka,
M.; Yamamoto, Y.; Ishimaru, T. J . Chem. Soc., Chem. Commun. 1984,
1705-1706.
(15) For other annulations of allylidene(triphenyl)phosphorane,
see: (a) Capuano, L.; Willmes, A. Liebigs Ann. Chem. 1982, 80-86.
(b) Capuano, L.; Triesch, T.; Willmes, A. Chem. Ber. 1983, 116, 3767-
3773. (c) Ipaktschi, J .; Saadatmandi, A. Liebigs Ann. Chem. 1984,
1989-1993. (d) Hatanaka, M.; Yamamoto, Y.; Ishimaru, T.; Takai, T.
Chem. Lett. 1985, 183-186.
form of ca. 1:1 mixture of the E- and Z-isomers and 2 is
a single Z-isomer,12 were directly subjected to the reac-
tion. When phosphonium bromide 1 was treated with
dibenzoylethylene (7) in a heterogeneous medium of
(16) (a) Barluenga, J .; Lopez, F.; Sanchez-Ferrando, F. Tetrahedron
Lett. 1988, 29, 381-384. (b) J ohnson, A. W. Ylides and Imines of
Phosphorus; J ohn Wiley & Sons, Inc.: New York, 1993; pp 198-201.
(c) Weiyu, D.; Zang, P.; Cao, W. Tetrahedron Lett. 1987, 28, 81-82.
(d) Weiyu, D.; Weiguo, C.; Zhenrong, X.; Yuan, Y.; Zhijian, S.; Zhiheng,
H. J . Chem. Soc., Perkin Trans. 1 1993, 855-858.
(17) Preliminary report: Himeda, Y.; Hatanaka, M.; Ueda, I. J .
Chem. Soc., Chem. Commun. 1995, 449-450. Himeda, Y.; Ueda, I.;
Hatanaka, M. Chem. Lett. 1996, 71-72.

One-Step Synthesis of Cyclopentadienes and Fulvenes
J . Org. Chem., Vol. 62, No. 19, 1997 6531
Sch em e 4
Ta ble 1. Syn th esis of Cyclop en ta d ien es fr om
Allyl(tr ip h en yl)p h osp h on iu m Br om id es a n d
Dia cyleth ylen es
occurred when unsymmetrical substrate 18 was allowed
to react with 1; cyclohexadiene 19 was obtained in 37%
yield. It should arise from the initial Michael addition
at the 3-position of 18 and subsequent internal Wittig
reaction with the reactive aldehyde.
cyclopentadiene
ratio of
phosphonium diacylethylene
isomersa
no. a :b:c:d
total
entry bromide (R1)
(R2)
yieldb/%
1
2
3
4
5
6
7
1 (Me)
1 (Me)
1 (Me)
2 (Ph)
2 (Ph)
3 (H)
7 (Ph)
8 (Me)
9 (SEt)
7 (Ph)
8 (Me)
7 (Ph)
8 (Me)
11
12
13
14
15
16
17
1:1:0:0
1:2:0:0
1:1:0:0
3:9:1:0
1:8:4:0
0:1:0:4
d only
80
53
32 (53c)
90
51
49
29
3 (H)
In order to determine the location of the double bonds
in the resulting cyclopentadienes, we tried to isolate the
isomers in a pure form. Although attempts to separate
by means of column chromatography or HPLC were
unsuccessful in all cases, 1,3-diene 11a and 1,4-diene 14b
were fortunately isolated in pure form by crystallization
from the corresponding isomeric mixtures. Compound
11a was assigned as the 1,3-diene structure on the basis
of the observation of a cross peak between the C-5
methine proton (δ 4.70) and the C-3 vinyl proton (δ 6.65)
in the COSY 1H NMR spectra. The accompanying isomer
must be 1,4-diene 11b, as indicated by an absorption (δ
3.50) due to the C-3 methylene protons. In agreement
with this assignment, pure 1,4-diene 14b showed two
singlet peaks due to the C-3 methylene (δ 3.88) and the
C-5′ methylene protons (δ 4.40) with the absence of any
signals due to vinyl protons. Thus, the structure and the
ratio of the 1,3-diene and the 1,4-diene produced in each
case was estimated from 1H NMR spectra of the crude
product in comparison with those of 11a and 14b. The
1H chemical shifts of the isomers are illustrated in Table
2. The generation of 2,4-dienes c (14c and 15c) from the
a
The ratio of isomers was estimated on the basis of their NMR
spectra. Isolated yield. c The yield obtained under anhydrous
conditions in THF in the presence of 1 equiv of NaHMDS.
b
dichloromethane and saturated aqueous NaHCO3 at
room temperature, the [3 + 2] annulation occurred nicely
and cyclopentadiene was obtained in 80% yield as a 1:1
mixture of 1,3-diene 11a and 1,4-diene 11b without
accompanying formation of the corresponding cyclohexa-
diene 10 (Scheme 4). The annulation is applicable to the
preparation of various cyclopentadienes as illustrated in
Table 1. When phosphonium bromide 1 was allowed to
react with diacetylethylene (8) in a similar manner, a
1:2 mixture of 1,3-diene 12a and 1,4-diene 12b was
obtained. Diethyl thiofumarate (9) afforded a 1:1 mixture
of 13a and 13b in 53% yield when the reaction was
carried out in THF using sodium hexamethydisilazide
(NaHMDS) as a base; a lower yield in the heterogeneous
medium is due to accompanying hydrolysis of 9. 2-Phe-
nylphosphonium bromide 2 also underwent annulation
in the heterogenous medium to give the corresponding
isomers along with alternate isomer 2,4-diene c. The
reaction of 2 with 7 gave 14a , 14b, and 14c in a ratio of
3:9:1 and that with 8 produced 15a , 15b, and 15c in a
ratio of 1:8:4 (entries 4 and 5). When phosphonium
bromide 3 having no substituent at the 2-position was
allowed to react with 7, a 1:4 mixture of 1,4-diene 16b
and 1,3-diene 16d was obtained. The reaction of 3 with
8 produced 1,3-diene 17d as the sole observed isomer in
29% yield. On the other hand, [3 + 3] annulation
1
reactions of 2 with 7 and 8 was estimated from H NMR
spectra of each product mixture especially on the basis
of observation of the cross peak between the C-1 methine
(δ 4.88 for 14c, δ 4.49 for 15c) and the C-3 vinyl proton
(δ 7.03 for 14c, δ 6.73 for 15c) in the COSY spectra. On
the other hand, the location of the double bonds in 1,3-
dienes d (16d and 17d ) was also determined in a similar
1
manner on the basis of the H NMR spectra.18

6532 J . Org. Chem., Vol. 62, No. 19, 1997
Himeda et al.
Ta ble 2. 1H Ch em ica l sh ifts (δ) of th e 1,3-Dien es
11a -15a a n d th e 1,4-Dien es 11b-15b
spectra.22 Evidence for the stereo- and regiochemical
arrangement was mainly obtained from the NOESY
spectra, which showed the cross peaks of the C-6 proton
with the C-7 proton, the C-5R proton, and the C-2 phenyl
protons. Interestingly, the dimerization is readily re-
versible. When a solution of dimer 20 in CDCl3 was left
at room temperature, NMR spectra showed the partial
liberation of monomers 16d and 16b within several hours
and, after a week, almost complete formation of a 4:1
1,3-diene a
1,4-diene b
no.
3-H
5-H
no.
3-H
5′-methylene
11a
12a
13a
14a
15a
6.65
6.00
5.95
6.84
6.22
4.70
3.67
3.79
4.93
3.92
11b
12b
13b
14b
15b
3.50
3.02
3.25
3.88
3.41
4.35
3.58
3.95
4.40
3.61
1
It is well-known that cyclopentadienes are usually
unstable and readily undergo dimerization or 1,5-sigma-
tropic migration.19 Those prepared above were stable for
at least a week at room temperature, except for trisub-
stituted dienes 16d , 16b, and 17d as described later. The
formation of the double-bond isomers can be rationalized
to come from either 1,5-sigmatropic migration or basic
isomerization of the initial formed 1,3-dienes a . Isomer-
ization of 11a was examined in order to make it clear.
Isomer 11a was stable at room temperature for at least
a week against 1,5-sigmatropic migration.20 However,
when 11a was stirred in a heterogeneous medium of
dichloromethane and saturated aqueous NaHCO3 in the
presence of a catalytic amount of 1 at room temperature,
migration of the double bond occurred smoothly and led
to the formation of a 1:1 equilibrium mixture of 11a and
11b. Deuterium-exchange experiment with a NaHCO3-
D2O solution afforded a 1:1 mixture of 3,5-dideuteriated
1,3-diene 11a -d2 and 3,3-dideuteriated 1,4-diene 11b-d2.
These findings indicate that the double-bond isomers
arise through an equilibrium process from the initially
formed 1,3-dienes a under the weakly basic reaction
conditions via cyclopentadienyl anion formation.
mixture of 16d and 16b with disappearance of the peaks
due to the dimer. Evaporation of the CDCl3 gave a
mixture of the isomeric dimers again. However, the
crude dimer was transformed into an unidentified poly-
meric substance upon further standing without solvent
for a week. Trisubstituted cyclopentadiene 17d did not
dimerize under the same conditions, and when left at
room temperature for a week, decomposed to a complex
mixture from which no dimer was detected.
Attempted annulation of allylidenephosphorane 21 and
the (3-phenylallylidene)phosphorane 22 with dibenzoyl-
ethylene (7) under various conditions failed to give any
cyclopentadienes. The stronger basicity of the non- and
semistabilized phosphoranes might trigger unfavorable
side reactions, and hence the use of stabilized phospho-
rane such as 4-6 seems to be essential for the present
annulation. Thus, these stabilized phosphoranes smoothly
underwent annulation with 1,2-diacylethylenes as de-
scribed above and provide a convenient method for the
preparation of tri- and tetrasubstituted cyclopentadienes.
The cyclopentadienes were obtained as mixtures of the
double-bond isomers arising from the corresponding 1,3-
dienes a via base-induced isomerization but not via 1,5-
sigmatropic migration. Therefore, the product distribu-
tion may depend on the thermodynamic stability of the
isomers. Dimerization was observed only for 16d , al-
though dimer 20 dissociated extremely readily to the
monomer in a solution. The different behavior of 16d
and 17d which did not effect the dimerization seems to
be due to the electronic character of their C-3 substitu-
ents. Each isomer of the tetrasubstituted cyclopenta-
dienes was stable against dimerization probably because
of steric reasons.
The trisubstituted cyclopentadienes prepared from 3
showed somewhat different behavior from the tetrasub-
stituted derivatives. When the 4:1 mixture of 16d and
16b was left in a condensed state at room temperature
for several hours, dimerization occurred to give a mixture
of two isomeric dimers, of which the major isomer 20 was
obtained as white powder while the minor one could not
be purified because of its lability.21 The structure of 20
was determined by a combination of COSY and NOESY
(18) Compound 16d showed the peak (δ 6.61) due to the C-4 vinyl
proton and the peaks (δ 3.53) due to the C-5 methylene protons, and
in addition the NOESY spectrum revealed the cross peak between the
C-4 vinyl proton (δ 6.61) and the C-3 phenyl protons. The COSY
spectrum of 17d indicated the cross peaks between the C-5 methylene
protons (δ 3.27) and the C-4 vinyl proton (δ 6.28) and between the
former and the C-3 methyl protons (δ 1.92).
(19) (a) McLean, S.; Hayes, P. Tetrahedron 1965, 21, 2313-2327,
2329-2342, 2343-2351. (b) Spangler, C. W. Chem. Rev. 1976, 76,
187-217.
(20) The sigmatropic migration occurred when 11a was heated in
refluxing benzene for 3 h and led to the formation of a 2:1 mixture of
11a and 11b.
F u lven e Syn th esis. Taking advantage of the pre-
dominant formation of [3 + 2] annulation products with
1,2-diacylethylenes, we next investigated the reaction of
the phosphoranes with 1,2-diacylacetylenes aiming at
(21) It was suggested from observation of the following peaks in 1H
NMR spectra that the isomeric dimer might be the endo isomer of 20:
3.40 (m, 1H, H-7), 2.86 (dd, J ) 9.9, 18.0 Hz, 1H, H-5), 2.53 (bd, J )
18.0 Hz, 1H, H-5), 2.44 (dd, J ) 1.8, 9.2 Hz, 1H, H-10), 2.01 (dd, J )
1.4, 9.2 Hz, 1H, H-10). However, a detailed examination was prevented
by difficulty of purification and ready dissociation to the monomers in
a solution.
(22) For dimerization of cyclopentadienylcarboxylate, see: (a) Fran-
klin, E.; Mack, C. H.; Rowland, S. P. J . Org. Chem. 1968, 33, 626-
632. (b) Minter, D. E.; Marchand, A. P.; Lu, S.-p. Magn. Reson. Chem.
1990, 28, 623-627.

One-Step Synthesis of Cyclopentadienes and Fulvenes
J . Org. Chem., Vol. 62, No. 19, 1997 6533
Ta ble 3. 13C a n d 1H Ch em ica l Sh ifts of Z-24
Sch em e 5
position
13C chemical shift (ppm)
1H chemical shift (ppm)
1
2
3
4
5
6
120.02
157.01
133.45
146.13
143.96
134.71
6.44
6.94
anisotropy of the ester carbonyl group.3c,23 Similarly, the
C-6 geometry of Z-24 was determined to be Z on the basis
of the C-6 proton chemical shift (δ 6.94).
one-step synthesis of substituted fulvenes. Annulation
of allylidenetriphenylphosphorane with alkynes attached
to electron-withdrawing functionality has been reported
only for the formation of substituted benzenes from
allylidenephosphorane and perfluoro alkynoates.16c,d The
annulation involves the first Michael addition at the
R-position of the phosphorane and subsequent ylide
interchange which is usually observed especially when
the reaction of phosphorane with alkynes was carried out
in aprotic solvents.16b We examined the reaction of
allylidenephosphorane with 1,2-diacylethylenes in the
heterogeneous medium described above to avoid the ylide
interchange.
When phosphonium bromide 1 was allowed to react
with dibenzoylacetylene (23) in the heterogeneous me-
dium of dichloromethane and saturated aqueous NaHCO3
at room temperature, fulvene Z-24 was obtained as
crystals in 88% yield (Scheme 5). The formation of the
corresponding [3 + 3] annulation product 26 was not
detected in the reaction mixture. Thus, Michael addition
of the phosphorane occurred at the γ-position, and
subsequent Wittig reaction favored the fulvene formation
in a fashion analogous to the reaction with 1,2-diacyl-
ethylenes. Annulation of phosphonium salt 3 having no
substituent at the C-2 position with 23 also gave the
geometrical isomers Z-25 and E-25 in 38% and 28%
yields, respectively. The ratio of Z- and E-isomers was
not affected by the reaction temperature; a 3:1 mixture
of Z-25 and E-25 was obtained in 25% yield when the
reaction was carried out at 0 °C. It is however noted that
the acetylene and 1,2-diacylethylenes are more efficient
substrates than R-halo ketones, because 3 did not effect
annulation with R-halo ketones but dimerization of the
corresponding phosphorane 6.12a The structure of Z-24
was fully confirmed by a combination of the CH-COSY
and long range CH-COSY spectra. The 13C and 1H
chemical shifts of Z-24 are given in Table 3. The
geometry of the exocyclic double bond was assigned on
the basis of the C-6 proton chemical shift. The exocyclic
C-6 proton of E-25 was observed at δ 8.34, while that of
Z-25 was centered at δ 7.08. It appears that the
downfield shift observed for E-25 is attributable to the
When the unsymmetrical substrate 27 was allowed to
react with 1 in a similar manner, E-28 and Z-28 were
isolated in 16% and 34% yields, respectively. No obser-
vation of the other regioisomers in the reaction mixture
indicates that the initial Michael addition occurs regi-
oselectively at the 3-position of 27. Isomer Z-28 was very
unstable in the condensed state and was transformed
easily into dimer 29.24 When a solution of 29 in CDCl3
was left at room temperature overnight, 1H NMR spectra
showed partial dissociation of 29 into Z-28, implying
reversibility of the dimerization. Structural confirmation
of dimer 29 was accomplished by a combination of the
COSY and NOESY spectra. Notable features of the
NOESY spectra are the cross peaks between the C-2
proton and the C-3 methyl protons, between the C-5′
vinyl proton and the C-7 methyl protons, and between
the C-3 methyl protons and the C-9 methyl protons.
These facts strongly support the stereo- and regiochemi-
cal arrangement of structure 29. In sharp contrast,
isomer E-28 was stable against dimerization after being
left at room temperature for a week. This may suggest
that approach of the two molecules of E-28 is inhibited
by the steric hindrance due to the E-oriented benzoyl
group at the 6′-position. In addition, comparison of the
behavior of Z-28 with that of Z-24 and Z-25 indicates
that the 4-phenyl substituent prevents the dimerization
owing to steric bulk.
Thus, the annulation of 1,2-diacylacetylene with al-
lylidenephosphorane provides efficient access to substi-
tuted fulvenes. The resulting 6-monoacylfulvenes, which
(23) The C-6 geometry was undoubtedly confirmed by the NOESY
spectra; the cross peak between the C-6 proton and the C-4 methyl
proton was observed for Z-28 but not for E-28.
(24) For dimerization of fulvene, see: (a) Uebersax, B.; Neuen-
schwander, M.; Kellerhals, H.-P. Helv. Chim. Acta 1982, 65, 74-88.
(b) Uebersax, B.; Neuenshwander, M.; Engel, P. Helv. Chim. Acta 1982,
65, 89-104.

6534 J . Org. Chem., Vol. 62, No. 19, 1997
Himeda et al.
Sch em e 6
Sch em e 7
are known only for a few examples,4e,11b were quite stable
except for Z-28 that dimerized readily. The distribution
of E- and Z-isomers in each case seems to depend on the
thermodynamic stability of the isomers, because isomer-
ization of the 6-substituent can occur smoothly under the
reaction conditions; E-25 gave a 1:1 mixture of Z-25 and
E-25 upon being stirred in saturated aqueous NaHCO3
and dichloromethane in the presence of a catalytic
amount of 3 at 30 °C for 12 h, while Z-25 afforded a 2:1
mixture of Z-25 and E-25 under the same conditions.25
Ca lcu la tion s. Both annulations should proceed in a
stepwise fashion as illustrated in Schemes 4 and 5. The
C-3 carbanion of the 1,4-dipolar resonance form of
allylidenephosphorane adds to 1,2-diacylethylene or 1,2-
diacylacetylene, and subsequent intramolecular Wittig
reactions provide cyclopentadiene or fulvene in a highly
regioselective manner. The observed high level of [3 +
2] annulation is interesting, especially for a fulvene-
forming reaction (Scheme 5) because an alternative [3 +
3] annulation would lead to the formation of much more
stable benzene derivatives. We have carried out molec-
ular orbital calculations on two model processes il-
lustrated in Schemes 6 and 7 to clarify the origin of the
high selectivity of the [3 + 2] annulation, especially for
the fulvene-forming reaction. All calculations were car-
ried out by the semiempirical PM3 method26 with the
Gaussian 92 package of programs;27 the three Ph groups
on P are replaced by H and other Ph and Et groups by
Me in order to make the calculations practical. The PM3
method has previously been shown to be capable of
successfully modeling a Wittig reaction.28 The use of the
rather simplified model is justified because we discuss
only the relative stability of the transition states of the
two competitive reaction routes for each compound (30
and 35 in Schemes 6 and 7). Since the Wittig reactions
proceed via the oxaphosphetane intermediates, two tran-
sition states, one for oxaphosphetane formation and the
other for oxaphosphetane decomposition, may have to be
considered for rationalizing the observed product selec-
tivities. However, the extensive study by Vedejs revealed
that oxaphosphetane reversal does not occur for a sta-
bilized ylide and hence that product selectivity is deter-
mined in the oxaphosphetane formation step.29 In the
present calculations, therefore, only the oxaphosphetane-
forming transition states were considered. Two ylides,
30 and 35, five products (32 and 34 for Scheme 6 and
(26) Stewart, J . J . P. J . Comput. Chem. 1989, 10, 209-220, 221-
264.
(27) Frisch, M. J .; Trucks, G. W.; Head-Gordon, M.; Gill, P. M.;
Wong, M. W.; Foresman, J . B.; J ohnson, B. G.; Schlegel, H. B.; Robb,
M. A.; Replogle, E. S.; Gomperts, R.; Andress, J . L.; Rachavachari, K.;
Binkley, J . S.; Gonzalez, C.; Martin, R. L.; Fox, D. J .; Defrees, D. J .;
Baker, J .; Stewart, J . J . P.; Pople, J . A. GAUSSIAN 92, Gaussian Inc.,
Pittsburgh, PA, 1992.
(25) Significant deuterium incorporation at any position of the
fulvene was not observed when the isomerization of E-25 was carried
out in D2O solution. The isomerization also occurred at room tem-
perature in an ether solution containing a weak base such as pyridine.
It is likely that the extremely facile isomerization proceeds via an
intermediary cyclopentadienyl anion produced by attack of a nucleo-
phile at the 6-position.
(28) Mari, F.; Lahti, P. M.; McEwen, W. E. Heteroatom Chem. 1991,
2, 265-276. Mari, F.; Lahti, P. M.; McEwen, W. E. J . Am. Chem. Soc.
1992, 114, 813-821.
(29) Vedejs, E.; Fleck, T. J . J . Am. Chem. Soc. 1989, 111, 5861-
5871. Vedejs, E. Topics in Stereochemistry: Allinger, N. L., Eliel, E.
L., Wilen, S. H., Eds; J ohn Wiley & Sons, Inc.: New York, 1994; Vol.
21, pp 1-157.

One-Step Synthesis of Cyclopentadienes and Fulvenes
J . Org. Chem., Vol. 62, No. 19, 1997 6535
F igu r e 1. Optimized structures: transition states TS1, TS2, TS3, TS4, and TS5 of oxaphosphetane-forming steps.
37, 39, and 41 for Scheme 7), five oxaphosphetane
intermediates, and five transition states leading to these
intermediates were fully optimized. Several conforma-
tional isomers were examined for each species including
the stereoisomeric pairs of 31, 33, TS1, and TS2, and
only the most stable ones are considered here. The
frequency calculations were carried out in order to
confirm that the calculated structures are a local mini-
mum or a transition state. Relative energies listed below
include zero-point energy correction.
As summarized in Scheme 6, a pair of transition states
for the oxaphosphetane formation (Figure 1) have much
different energies; TS2 which eventually gives cyclohexa-
diene is 5.0 kcal/mol higher in energy than TS1 which
leads to the cyclopentadiene derivative.30 These give two
oxaphosphetanes that have very similar stabilities. Thus,
the calculations are consistent with the observed product
selectivity. For the fulvene-forming reaction, two iso-
meric fulvenes, in addition to a six-membered product,
were considered, and the results are summarized in
Scheme 7. The two fulvene isomers were found to have
similar stabilities, consistent with the fact that the
reaction gave the mixture of the two isomers in all cases.
Discussion of the subtle energy difference of the two
isomers is probably not justified due to the limited
accuracy of the semiempirical calculations. It should be
noted, however, that the six-membered product 41 and
the oxaphosphetane 40 leading to 41 have considerably
lower energies compared to the corresponding five-
membered species. Thus, the formation of the benzene
derivative is thermodynamically favored over the fulvene
derivatives. By contrast, the oxaphosphetane formation
transition state in the benzene-forming pathway was
found to be higher in energy than the transition states
for the fulvene-forming pathways. Clearly observed
exclusive fulvene formation is kinetically controlled in
nature, which is fully consistent with the results reported
by Vedejs.29
Since the benzene-forming pathway has a more stable
oxaphosphetane and a less stable transition state than
the fulvene-forming pathway, there should be some factor
which makes the oxaphosphetane stable. A major origin
may be an effective overlap of the two double bonds in
oxaphosphetane 40; the dihedral angle (C2-C3-C4-C5)
in oxaphosphetane 40 is much smaller (1.8°) than that
(C2-C3-C4-C4′, 7.6°) in oxaphosphetane 38. It is note-
worthy that the dihedral angle (C2-C3-C4-C5) in transi-
tion state TS5 is larger (20.0°) than that (C2-C3-C4-
C4′, 16.0°) in TS4, consistent with the relative stability
of the two transition states.
Con clu sion
The convenient syntheses of substituted cyclopenta-
dienes and fulvenes were accomplished. In the [3 + 2]
annulations, allylidenetriphenylphosporane acts as the
1,3-bifunctional unit having two nucleophic centers at the
R- and γ-positions of the electron-delocalized structure.
The utility of the phosphorane in annulation largely
depends on which site effects nucleophilic addition. The
alkylation occurs almost exclusively at the γ-position as
demonstrated here and in the previous cyclopentadiene
formation with R-halo ketone. This might be due to the
steric hindrance at the R-position by the bulky triph-
enylphosphorus group. In addition, the present work
demonstrated high regioselectivity of the subsequent
intramolecular Wittig reaction for the 5-membered ring
construction. The preference may be due to kinetic
control as indicated by calculations.
Exp er im en ta l Section
(30) The several conformational isomers were each examined for
pairs of the stereoisomers of TS1 and TS2, and the most stable
transition states are depicted in Figure 1. The relative energies for
the transition states and the oxaphosphetane stereoisomers that can
be derived from those are listed in Scheme 6.
Melting points were obtained on a hot stage apparatus and
are uncorrected. IR spectra were recorded on a J ASCO FT/
IR-5300 spectrometer. 1H NMR spectra were measured at 300

6536 J . Org. Chem., Vol. 62, No. 19, 1997
Himeda et al.
MHz in CDCl3 on a Varian Gemini 300BB spectrometer, using
SiMe4 as the internal standard. 13C NMR were recorded at
75 MHz on the spectrometer, and the solvent peak (CDCl3, δ
77.0) was used for the internal standard. Mass spectra were
recorded on a Hitachi M-80B spectrometer. Flash chroma-
tography was performed on Wakogel C-300. The extracts were
dried over MgSO4 and evaporated under reduced pressure.
CH2Cl2 was distilled from CaH2. THF was distilled from
sodium benzophenone ketyl.
Eth yl 2-Meth yl-5-(2-oxo-2-p h en yleth yl)-4-p h en yl-1,3-
cyclop en ta d ien e-1-ca r boxyla te (11a ) a n d 1,4-Dien e Iso-
m er (11b). Saturated aqueous NaHCO3 (10 mL) was mixed
with a solution of phosphonium bromide 1 (469 mg, 1.0 mmol)
in dichlorometane (10 mL). To this well-stirred mixture was
added a solution of 1,2-dibenzoylethylene (7, 236 mg, 1.0 mmol)
in dichloromethane (2 mL), and the mixture was stirred at
room temperature for 12 h under nitrogen. The aqueous layer
was separated and extracted with dichloromethane. The
combined organic layers were washed with water, dried, and
then evaporated. The residue was passed through a short
column of silica gel to remove triphenylphosphine oxide and
further purified by flash chromatography with ethyl acetate/
hexane (1:5) to afford a 1:1 mixture of 11a and 11b as an oil
12a and 12b as an oil: IR (neat) 1705, 1632, 1582, 1557, 1445,
1
1375 cm-1; H NMR (300 MHz, CDCl3) δ 6.00 (d, J ) 1.4 Hz,
1
1
1 × /3H), 4.25-4.14 (m, 2H), 3.67 (bs, 1 × /3H), 3.58 (s, 2 ×
1
2/3H), 3.02 (s, 2 × 2/3H), 3.00 (dd, J ) 16.6, 4.1 Hz, 1 × /3H),
1
2.67 (dd, J ) 16.6, 7.4 Hz, 1 × /3H), 2.28 (s, 3H), 2.18 (s, 3 ×
1
1
2/3H), 2.13 (s, 3 × /3H), 1.94 (d, J ) 1.4 Hz, 3 × /3H), 1.88 (s,
3 × 2/3H), 1.31 (t, J ) 7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3)
δ 207.07, 206.92, 165.30, 164.66, 156.15, 155.53, 153.68,
136.91, 132.34, 131.47, 131.37, 130.07, 59.82, 59.42, 50.83,
42.47, 41.79, 30.30, 29.60, 16.32, 15.83, 15.35, 14.49, 14.44,
14.32, 13.14; HRMS calcd for C13H18O3 222.1255, found
222.1243.
Eth yl 4-(Eth ylth io)-5-(2-(eth ylth io)-2-oxoeth yl)-2-m eth -
yl-1,3-cyclop en ta d ien e-1-ca r boxyla te (13a ) a n d 1,4-Dien e
Isom er (13b). To a stirred suspension of phosphonium
bromide 1 (469 mg, 1.0 mmol) in THF (20 mL) was added a 1
M sodium bis(trimethylsilyl)amide-THF solution (1.0 mL) at
-30 °C under nitrogen, and the mixture was stirred for 1 h at
0 °C. The yellow suspension was cooled at -30 °C and treated
with a solution of diethyl thiofumarate (9) (204 mg, 1.0 mmol)
in THF (2 mL). The mixture was stirred at room temperature
for 48 h and evaporated. The residue was chromatographed
to give a 1:1 mixture of 13a and 13b as an oil (166 mg, 53%):
(277 mg, 80%): IR (neat) 1690, 1616, 1489, 1447, 1375 cm-1
;
IR (neat) 1692, 1609, 1497, 1375 cm-1
;
1H NMR (300 MHz,
1
1H NMR (300 MHz, CDCl3) δ 8.02 (bd, J ) 8.0 Hz, 2 × /2H),
CDCl3) δ 5.95 (s, 1 × 1/2H), 4.27-4.16 (m, 2H), 3.95 (s, 2 ×
1
1
1
7.86 (bd, J ) 8.0 Hz, 2 × /2H), 7.56-7.23 (m, 8H), 6.65 (bs, 1
1/2H), 3.81-3.77 (m, 1 × /2H), 3.25 (s, 2 × /2H), 3.13 (dd, J )
1
1
1
1
1
× /2H), 4.70 (m, 1 × /2H), 4.35 (s, 2 × /2H), 4.11-3.97 (m,
15.4, 4.1 Hz, 1 × /2H), 3.00 (dd, J ) 15.4, 7.1 Hz, 1 × /2H),
1 1
1
1
2H), 3.50 (s, 2 × /2H), 3.46 (dd, J ) 6.1, 17.0 Hz, 1 × /2H),
2.91-2.79 (m, 6 × /2H), 2.73 (q, J ) 7.4 Hz, 2 × /2H), 2.35 (s,
1 1
1
1
3.12 (dd, J ) 3.5, 17.0 Hz, 1 × /2H), 2.42 (s, 3 × /2H), 2.41 (d,
3 × /2H), 2.30 (d, J ) 2.2 Hz, 3 × /2H), 1.35 (t, J ) 7.4 Hz, 3
1
1
1
1
J ) 1.4 Hz, 3 × /2H), 1.08 (t, J ) 7.1 Hz, 3 × /2H), 1.07 (t, J
) 7.1 Hz, 3 × 1/2H); 13C NMR (75 MHz, CDCl3) δ 198.04,
197.58, 164.79, 164.50, 156.26, 155.57, 155.28, 141.10, 137.00,
136.88, 136.42, 133.71, 133.31, 132.76, 132.69, 132.15, 131.38,
128.70, 128.38, 128.32, 128.28, 128.01, 127.97, 127.92, 127.77,
126.79, 126.69, 59.67, 59.35, 49.59, 47.27, 38.14, 38.04, 16.32,
15.64, 14.00, 13.90.
× /2H), 1.31 (t, J ) 7.1 Hz, 3 × /2H), 1.31 (t, J ) 7.1 Hz, 3 ×
1/2H), 1.24 (t, J ) 7.4 Hz, 3 × /2H), 1.22 (t, J ) 7.4 Hz, 3H);
1
13C NMR (75 MHz, CDCl3) δ 197.10, 196.37, 164.32, 164.05,
156.41, 155.99, 154.66, 138.17, 134.67, 131.87, 128.84, 128.09,
60.09, 59.41, 51.46, 50.06, 44.40, 43.10, 28.49, 26.75, 23.40,
23.25, 16.34, 15.70, 15.24, 14.68, 14.64, 14.43, 14.17, 13.51;
HRMS calcd for C15H22O3S2 314.1009, found 314.0991.
Eth yl 2,4-d ip h en yl-5-(2-oxo-2-p h en yleth yl)-1,3-cyclo-
p en ta d ien e-1-ca r boxyla te (14a ), 1,4-d ien e isom er (14b),
a n d 2,4-d ien e isom er (14c) were prepared from 2 and 7
according to the procedure described for the preparation of 11a
and 11b to afford a 3:9:1 mixture of 14a , 14b, and 14c as an
Trituration of the resulting oil in ethyl acetate-hexane gave
pure crstals of 11a : mp 115.5-117 °C; IR (Nujol) 1688, 1615,
1489, 1445, 1375 cm-1 1H NMR (300 MHz, CDCl3, assign-
;
ments were assisted by 1H-1H COSY experiments) δ 7.86 (bd,
J ) 8.0 Hz, 2H, ortho H of COPh), 7.53-7.23 (m, 8H, Ph),
6.65 (bs, 1H, 3-H), 4.70 (m, 1H, 5-H), 4.10-3.97 (m, 2H,
OCH2CH3), 3.46 (dd, J ) 6.1, 17.0 Hz, 1H, 5-CH2), 3.12 (dd, J
) 3.5, 17.0 Hz, 1H, 5-CH2), 2.41 (d, J ) 1.4 Hz, 3H, 2-CH3),
1.08 (t, J ) 7.1 Hz, 3H, OCH2CH3); 13C NMR (75 MHz, CDCl3)
δ 197.62, 164.57, 156.27, 155.33, 136.99, 133.72, 132.68,
131.38, 128.69, 128.26, 128.00, 127.92, 126.79, 59.37, 47.25,
38.03, 15.62, 13.97; UV λmax (MeOH) 330.5 (14 800), 235 nm
(16 500). Anal. Calcd for C23H22O3: H, 6.40; C, 79.74.
Found: H, 6.33; C, 79.76.
oil in 90% yield: IR (neat) 1692, 1597, 1493, 1447 cm-1
;
1H
9
NMR (300 MHz, CDCl3) δ 8.02 (bd, J ) 8.4 Hz, 2 × /13H),
1
7.95 (bd, J ) 8.4 Hz, 2 × /13H), 7.88 (bd, J ) 8.4 Hz, 2 ×
3/13H), 7.57-7.26 (m, 13H), 7.03 (d, J ) 1.0 Hz, 1 × /13H), 6.84
1
3
3
(d, J ) 1.0 Hz, 1 × /13H), 4.93 (m, 1 × /13H), 4.88 (d, J ) 1.0
1
9
Hz, 1 × /13H), 4.40 (s, 2 × /13H), 4.35-3.97 (m, 2H), 3.88 (s,
9
3
2 × /13H), 3.59 (dd, J ) 6.1, 16.8 Hz, 1 × /13H), 3.25 (dd, J )
3
1
3.7, 16.8 Hz, 1 × /13H), 1.03 (t, J ) 7.1 Hz, 3 × /13H), 0.98 (t,
J ) 7.1 Hz, 3 × /13H), 0.97 (t, J ) 7.1 Hz, 3 × /13H); 13C NMR
(75 MHz, CDCl3) δ 197.77, 197.56, 197.47, 165.88, 164.10,
156.35, 155.29, 151.02, 143.52, 136.84, 136.19, 135.98, 133.89,
133.86, 133.02, 130.89, 130.75, 128.90, 128.67, 128.56, 128.44,
128.30, 128.18, 128.09, 127.98, 127.90, 127.84, 127.73, 127.69,
127.17, 126.99, 125.52, 60.35, 59.82, 48.53, 48.06, 38.39, 37.56,
9
3
Isom er iza tion of 11a in D2O. A solution of NaHCO3 (0.5
g, 6.0 mmol) in D2O (5 mL) was mixed with a solution of 11a
(98 mg, 0.283 mmol) in dichlorometane (10 mL). Phosphonium
bromide 1 (40 mg, 0.085 mmol) was added to the well-stirred
mixture, and the mixture was stirred at room temperature for
24 h under nitrogen. The aqueous layer was separated and
extracted with dichloromethane. The combined organic layers
were washed with water, dried, and evaporated. Purification
by flash chromatography of the residue gave a 1:1 mixture of
deuterated cyclopentadienes 11a -d2 and 11b-d2 as an oil (85
13.81, 13.61; HRMS calcd for C28
H24O3 408.1724, found
408.1691. Trituration of the resulting oil in ethyl ether-
hexane gave pure crstals of 14b: mp 110.8-112.0 °C ; IR
(Nujol) 1705, 1692, 1597, 1493, 1446, 1373 cm-1; 1H NMR (300
MHz, CDCl3) δ 8.02 (bd, J ) 8.4 Hz, 2H), 7.57-7.26 (m, 13H),
4.40 (s, 2H), 4.03 (q, J ) 7.1 Hz, 2H), 3.88 (s, 2H), 0.98 (t, J )
7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 197.78, 165.91,
151.03, 143.55, 136.91, 136.25, 136.05, 133.96, 133.03, 128.59,
128.22, 128.18, 128.02, 127.93, 127.76, 127.20, 60.37, 48.12,
37.59, 13.64; UV λmax (MeOH) 324.0 (11 800), 243.5 nm
(28 200). Anal. Calcd for C28H24O3: H, 5.92; C, 82.33.
Found: H, 5.83; C, 82.22.
mg, 86%): IR (neat) 1690, 1599, 1489, 1447 cm-1
;
1H NMR
1
(300 MHz, CDCl3) δ 8.02 (bd, J ) 8.0 Hz, 2 × /2H), 7.86 (bd,
1
1
J ) 8.0 Hz, 2 × /2H), 7.56-7.23 (m, 8H), 4.35 (s, 2 × /2H),
1
4.11-3.97 (m, 2H), 3.46 (d, J ) 17.0 Hz, 1 × /2H), 3.12 (d, J
1
1
1
) 17.0 Hz, 1 × /2H), 2.42 (s, 3 × /2H), 2.41 (s, 3 × /2H), 1.08
(t, J ) 7.1 Hz, 3 × 1/2H), 1.07 (t, J ) 7.1 Hz, 3 × 1/2H); 13C
NMR (75 MHz, CDCl3) δ 198.04, 197.58, 164.79, 164.50,
156.26, 155.57, 155.28, 141.10, 137.00, 136.88, 136.42, 133.71,
133.31, 132.76, 132.69, 132.15, 128.70, 128.38, 128.32, 128.28,
127.97, 127.92, 127.77, 126.79, 126.69, 59.67, 59.35, 38.14,
38.04, 16.32, 15.64, 14.00, 13.90; HRMS calcd for C23H20D2O3
348.1693, found 348.1701.
Eth yl 4-m eth yl-5-(2-oxop r op yl)-2-p h en yl-1,3-cyclop en -
ta d ien e-1-ca r boxyla te (15a ), 1,4-d ien e isom er (15b), a n d
2,4-d ien e isom er (15c) were prepared from 2 and 8 according
to the procedure described for the preparation of 11a and 11b
to afford a 1:8:4 mixture of 15a , 15b, and 15c as an oil in 51%
1
Eth yl 2,4-d im eth yl-5-(2-oxop r op yl)-1,3-cyclop en ta d i-
en e-1-ca r boxyla te (12a ) a n d 1,4-d ien e isom er (12b) were
prepared from 1 and 8 according to the procedure described
for the preparation of 11a and 11b to afford a 1:2 mixture of
yield: IR (neat) 1715, 1631, 1601, 1559 cm-1; H NMR (300
MHz, CDCl3) δ 7.45-7.15 (m, 5H), 6.73 (d, J ) 1.0 Hz, 1 ×
1
4
4/13H), 6.22 (bs, 1 × /13H), 4.49 (bs, 1 × /13H), 4.12 (q, J ) 7.1
8
5
Hz, 2 × /13H), 4.12-4.00 (m, 2 × /13H), 3.92 (ddd, J ) 7.3,

One-Step Synthesis of Cyclopentadienes and Fulvenes
J . Org. Chem., Vol. 62, No. 19, 1997 6537
1
8
8
4.1, 1.1 Hz, 1 × /13H), 3.61 (s, 2 × /13H), 3.41 (s, 2 × /13H),
cm-1
;
1H NMR (300 MHz, CDCl3, 0 °C, assignments were
1
3.11 (dd, J ) 16.5, 4.1 Hz, 1 × /13H), 2.77 (dd, J ) 16.5, 7.3
assisted by 1H-1H COSY and NOESY experiments) δ 7.92 (bd,
J ) 8.5 Hz, 2H, ortho H of COPh), 7.81 (bd, J ) 8.5 Hz, 2H,
ortho H of COPh), 7.56-7.20 (m, 16H, Ph), 4.30 (d, J ) 17.7
Hz, 1H, CH2COPh), 4.15-3.99 (m, 2H, OCH2CH3), 3.94-3.77
(m, 5H, OCH2CH3, CH2COPh), 3.56 (bd, J ) 9.6 Hz, 1H, 6-H),
3.25 (dd, J ) 9.6, 17.5 Hz, 1H, 5-HR), 3.01 (s, 1H, H7), 2.58
(dd, J ) 3.4, 17.5 Hz, 1H, 5-Hâ), 2.51 (d, J ) 8.5 Hz, 1H, 10-
Hanti), 2.36 (d, J ) 8.5 Hz, 1H, 10-Hsyn), 1.01 (t, J ) 7.1 Hz,
3H, OCH2CH3), 0.98 (t, J ) 7.1 Hz, 3H, OCH2CH3); 13C NMR
(75 MHz, CDCl3, 0 °C) δ 198.16, 196.90, 172.08, 171.99, 148.51,
148.37, 137.54, 136.60, 136.55, 136.03, 133.78, 133.72, 133.03,
132.94, 128.56, 128.50, 128.37, 128.28, 127.90, 127.74, 127.39,
127.25, 127.16, 126.76, 67.20, 61.05, 60.78, 52.19, 47.85, 46.76,
42.01, 37.98, 37.84, 37.79, 13.78, 13.72; UV λmax (MeOH) 244.0
nm (37 900). Anal. Calcd for C44H40O6: H, 6.06; C, 79.49.
Found: H, 6.05; C, 79.24.
1
8
4
Hz, 1 × /13H), 2.22 (s, 3 × /13H), 2.20 (s, 3 × /13H), 1.99 (s, 3
8
4
× /13H), 1.96 (d, J ) 1.0 Hz, 3 × /13H), 1.11 (t, J ) 7.1 Hz, 3
1
4
× /13H), 1.10 (t, J ) 7.1 Hz, 3 × /13H), 1.10 (t, J ) 7.1 Hz, 3
× /13H); 13C NMR (75 MHz, CDCl3) δ 206.57, 205.85, 170.34,
8
166.26, 149.41, 144.51, 141.45, 139.94, 136.25, 134.56, 133.18,
132.10, 130.60, 128.64, 128.57, 128.06, 127.91, 127.66, 127.52,
127.14, 125.40, 61.18, 60.41, 60.18, 49.15, 41.90, 41.37, 29.70,
29.65, 14.09, 13.78, 13.47, 13.21; HRMS calcd for C18H20O3
284.1411, found 284.1405.
Eth yl 5-(2-oxo-2-p h en yleth yl)-4-p h en yl-1,4-cyclop en -
ta d ien e-1-ca r boxyla te (16b) a n d eth yl 2-(2-oxo-2-p h en yl-
eth yl)-3-p h en yl-1,3-cyclop en ta d ien e-1-ca r boxyla te (16d )
were prepared from 3 and 7 according to the procedure
described for the preparation of 11a and 11b to afford a 1:4
mixture of 16b and 16d as an oil in 49% yield: 1H NMR (300
MHz, CDCl3, assignments were assisted by 1H-1H COSY and
(Z)-Eth yl 2-Meth yl-5-(2-oxo-2-p h en yleth ylen e)-4-p h en -
yl-1,3-cyclop en t a d ien e-1-ca r boxyla t e (Z-24). Phospho-
nium bromide 1 (469 mg, 1.0 mmole) was allowed to react with
23 (234 mg, 1.0 mmole) according to the procedure described
for the preparation of cyclopentadienes 11a and 11b. Purifica-
tion by flash chromatography with ethyl acetate/hexane (1:5)
of the crude product afforded Z-24 (303 mg, 88%) as plates:
mp 104.5-106.0 °C (ethyl acetate-hexane); IR (Nujol) 1715,
1663, 1595 cm-1; 1H NMR (300 MHz, CDCl3, assignments were
assisted by 1H-1H COSY and NOESY experiments) δ 7.95 (bd,
J ) 8.5 Hz, 2H, ortho H of COPh), 7.57-7.36 (m, 8H, Ph),
6.94 (bs, 1H, dCHCOPh), 6.44 (bs, 1H, 3-H), 3.84 (q, J ) 7.1
Hz, 2H, OCH2CH3), 2.37 (bs, 3H, 2-Me), 0.92 (t, J ) 7.1 Hz,
3H, OCH2CH3); 13C NMR (75 MHz, CDCl3) δ 193.66, 164.25,
157.01, 146.13, 143.96, 136.78, 134.71, 133.95, 133.45, 133.37,
129.40, 129.02, 128.64, 128.18, 120.02, 59.78, 15.93, 13.73; UV
λmax (MeOH) 458.0 (2200), 424.0 (2400), 276.5 (22 000), 237.0
nm (26 000). Anal. Calcd for C23H20O3: H, 5.85; C, 80.20.
Found: H, 5.82; C, 80.14.
1
NOESY experiments) δ 8.03 (bd, J ) 8.5 Hz, 2 × /5H, ortho
4
H of COPh), 7.95 (bd, J ) 8.5 Hz, 2 × /5H, ortho H of COPh),
1
7.54-7.25 (m, 8H, Ph), 7.39 (bs, 1 × /5H, 2-H), 6.61 (bs, 1 ×
4/5H, 4-H), 4.52 (s, 2 × /5H, 2-CH2), 4.41 (s, 2 × /5H, 5-CH2),
4
1
4
4.13 (q, J ) 7.1 Hz, 2 × /5H, OCH2CH3), 4.11 (q, J ) 7.1 Hz,
2 × 1/5H, OCH2CH3), 3.53 (bs, 2 × 4/5H, 5-H), 3.53 (bs, 2 ×
1/5H, 3-H), 1.15 (t, J ) 7.1 Hz, 3 × /5H, OCH2CH3), 1.14 (t, J
4
) 7.1 Hz, 3 × /5H, OCH2CH3); 13C NMR (75 MHz, CDCl3) δ
1
198.02, 196.74, 164.49, 164.14, 151.30, 149.80, 145.56, 141.99,
139.42, 137.00, 135.67, 135.06, 133.91, 133.00, 132.91, 132.61,
128.51, 128.45, 128.31, 128.15, 128.06, 128.00, 127.55, 127.15,
60.17, 59.81, 43.81, 41.41, 38.13, 37.76, 14.22, 14.06; HRMS
calcd for C22H20O3 332.1411, found 332.1436. The oil was
converted into a dimeric mixture mainly containing 20 on
leaving at room temperature overnight.
Eth yl 3-m eth yl-2-(2-oxop r op yl)-1,3-cyclop en ta d ien e-1-
ca r boxyla te (17d ) was prepared from 3 and 8 according to
the procedure described for the preparation of 11a and 11b to
afford 17d as an oil in 29% yield: IR (neat) 1698, 1628, 1557,
(Z)- a n d (E)-eth yl 5-(2-oxo-2-p h en yleth ylen e)-4-p h en yl-
1,3-cyclop en ta d ien e-1-ca r boxyla tes (Z-25 a n d E-25) were
prepared from 2 and 23 according to the procedure described
for the preparation of Z-24 to afford Z-25 (38%) and E-25
1444 cm-1 1H NMR (300 MHz, CDCl3, assignments were
;
assisted by 1H-1H COSY experiments) δ 6.28 (bs, 1H, 4-H),
4.21 (q, J ) 7.1 Hz, 2H, OCH2CH3), 4.00 (s, 2H, COCH2), 3.27
(bs, 2H, 5-H), 2.23 (s, 3H, COCH3), 1.92 (m, 3H, 3-CH3), 1.31
(t, J ) 7.1 Hz, 3H, OCH2CH3); 13C NMR (75 MHz, CDCl3) δ
205.24, 164.72, 152.40, 143.66, 133.09, 132.56, 59.78, 42.42,
40.84, 29.94, 14.42, 13.60; UV λmax (MeOH) 285 nm (22 600);
HRMS calcd for C12H16O3 208.1099, found 208.1091.
(28%). Z-25: oil; IR (neat) 1705, 1669, 1597 cm-1 1H NMR
;
(300 MHz, CDCl3 assignments were assisted by 1H-1H COSY
experiments) δ 7.94 (bd, J ) 8.4 Hz, 2H, ortho H of COPh),
7.57-7.36 (m, 9H, Ph, 2-H), 7.08 (bs, 1H, dCHCOPh), 6.58
(d, J ) 2.6 Hz, 1H, 3-H), 3.91 (q, J ) 7.1 Hz, 2H, OCH2CH3),
1.00 (t, J ) 7.1 Hz, 3H, OCH2CH3); 13C NMR (75 MHz, CDCl3)
δ 193.67, 163.26, 145.67, 144.72, 143.39, 138.72, 136.66,
134.05, 133.39, 129.45, 129.01, 128.69, 128.63, 128.45, 128.27,
E t h yl 2-Met h yl-6-(1-oxoet h yl)-1,3-cycloh exa d ien e-1-
ca r boxyla te (19). Phosphonium bromide 1 (469 mg, 1.0
mmol) was allowed to react with 4-oxo-2-pentenal (18) (100
mg, 1.0 mmol) according to the procedure described for the
preparation of 11a and 11b. Flash chromatography of the
crude product gave 19 (76 mg, 37%) as an oil: IR (neat) 1711,
125.57, 60.08, 13.86; UV λmax
(2800), 243.0 nm (26 600); HRMS calcd for C22H18O3 330.1255,
found 330.1238. E-25: oil; IR (neat) 1701, 1659, 1597 cm-1
(MeOH) 458.0 (2600), 424.0
;
1H NMR (300 MHz, CDCl3 assignments were assisted by 1H-
1H COSY experiments) δ 8.34 (dd, J ) 0.8, 1.2 Hz, 1H,
dCHCOPh), 7.57 (bd, J ) 8.4 Hz, 2H, ortho H of COPh), 7.47
(dd, J ) 0.8, 2.6 Hz, 1H, 2-H), 7.43 (bt, J ) 7.4 Hz, 1H, para
H of COPh), 7.27 (bt, J ) 7.4 Hz, 2H, meta H of COPh), 7.10-
6.90 (m, 5H, Ph), 6.43 (dd, J ) 1.2, 2.6 Hz, 1H, 3-H), 4.33 (q,
1574, 1400, 1356 cm-1 1H NMR (300 MHz, CDCl3, assign-
;
ments were assisted by 1H-1H COSY experiments) δ 6.04 (ddd,
J ) 9.4, 5.7, 2.9 Hz, 1H, 4-H), 5.91 (ddd, J ) 9.4, 2.7, 0.9 Hz,
1H, 3-H), 4.24 (q, J ) 7.1 Hz, 2H, OCH2CH3), 3.59 (dd, J )
9.1, 3.5 Hz, 1H, 6-H), 2.76 (dddd, J ) 18.0, 5.7, 3.5, 0.9 Hz,
1H, 5-H), 2.41 (dddd, J ) 18.0, 9.1, 2.9, 2.7 Hz, 1H, 5-H), 2.25
(bs, 3H, 2-CH3), 2.13 (s, 3H, COCH3), 1.31 (t, J ) 7.1 Hz, 3H,
OCH2CH3); 13C NMR (75 MHz, CDCl3, assignments were
assisted by 13C-1H COSY, and long range 13C-1H COSY
experiments) δ 209.13, 167.73, 145.11, 131.34 (4-CH), 130.62
(3-CH), 120.25, 60.37 (OCH2CH3), 46.44 (6-CH), 27.99 (COMe),
25.77 (5-CH2), 20.84 (2-Me), 14.25 (OCH2CH3); UV λmax (MeOH)
286.5 nm (7000); HRMS calcd for C12H16O3 208.1099, found
208.1118.
J ) 7.1 Hz, 2H, OCH2
CH3), 1.39 (t, J ) 7.1 Hz, 3H, OCH2CH3);
13C NMR (75 MHz, CDCl3) δ 194.42, 163.55, 144.63, 143,67,
143.05, 139.76, 136.87, 135.25, 133.23, 131.22, 128.97, 128.80,
128.11, 127.68, 127.52, 125.91, 60.11, 14.37; UV λmax (MeOH)
458.0 (2400), 424.0 (2500), 242.5 nm (27 100); HRMS calcd for
C22H18O3 330.1255, found 330.1229.
1-P h en yl-2-p en tyn e-1,4-d ion e (27). A solution of 1-phen-
yl-2-pentene-1,4-dione (730 mg, 4.2 mmol) in CCl4 (30 mL) was
treated with Br2 (0.22 mL, 4.2 mmol), and the mixture was
stirred at room temperature for 1 h and then evaporated. The
residue was dissolved in acetone (30 mL) and treated with
triethylamine (0.85 g, 8.4 mmol). After the mixture was
refluxed for 1 h, the precipitated triethylammonium bromide
was removed by filtration, and the filtrate was evaporated
under reduced pressure. Flash chromatography with ethyl
acetate/hexane (1:5) of the residue gave 27 (365 mg, 51%) as
Isola tion of 1,4-Bis(eth oxyca r bon yl)-3,9-bis(2-p h en yl-
2-o x o e t h y l)-2,8-d ip h e n y lt r ic y c lo [5.2.1.02,6]d e c a -3,8-
d ien e(20). The 1:4 mixture of 16b and 16d (276 mg, 0.83
mmol) in neat was heated at 40 °C for 30 min. The oil was
taken into a 1:1 mixtue of ethyl ether and hexane (20 mL),
and the solution was slowly condensed on a cold water bath
until a white powder started to form. The powder was
collected by filtration and washed several times with hexane
to give 20 as white powder (20 mg, 8%). The filtrate contained
mainly monomers 16b and 16d because of ready dissociation
of 20 in the solution. 20: IR (neat) 1736, 1688, 1597, 1447
a pale yellow oil: IR (neat) 1694, 1651, 1597, 1451 cm-1; H
NMR (300 MHz, CDCl3) δ 8.15 (bd, J ) 8.4 Hz, 2H), 7.68 (tt,
J ) 7.4, 1.4 Hz, 1H), 7.53 (bt, J ) 7.4 Hz, 2H), 2.52 (s, 3H);
1

6538 J . Org. Chem., Vol. 62, No. 19, 1997
Himeda et al.
13C NMR (75 MHz, CDCl3) δ 182.86, 176.52, 135.59, 135.14,
129.69, 128.91, 86.69, 83.16, 32.56; HRMS calcd for C11H8O2
172.0524, found 172.0586.
Found: H, 6.41; C, 76.60; HRMS calcd for C18H18O3 282.1255,
found 282.1285. Anal. Calcd for C18H18O3: H, 6.43; C, 76.57.
(5Z,10Z)-5,10-Bis(b en zoylm et h ylen e)-1,4-b is(et h oxy-
ca r bon yl)-3,6,7,9-tetr a m eth yltr icyclo[5.2.1.02,6]d eca -3,8-
d ien e (29). The Z-isomer Z-28 dimerized within several hours
to afford the dimer 29 quantitatively: oil; IR (neat) 1732, 1657,
(Z)- a n d (E)-eth yl 2,4-d im eth yl-5-(2-oxo-2-p h en yleth -
ylen e)-1,3-cyclopen tadien e-1-car boxylates (Z-28 an d E-28)
were prepared from 2 and 23 according to the procedure
described for the preparation of Z-24 to afford Z-28 (34%) and
E-28 (16%), in which Z-28 dimerized readily upon being left
at room temperature after evaporation of the solvent and hence
the physical data were taken as immediately as possible.
1599 cm-1 1H NMR (300 MHz, CDCl3 assignments were
;
1
assisted by H-1H COSY and NOESY experiments) δ 7.96-
7.90 (m, 4H, ortho H of COPh), 7.60-7.42 (m, 6H, Ph), 6.51
(s, 1H, 5-CH), 6.21 (s, 1H, 10-CH), 5.72 (q, J ) 1.6 Hz, 1H,
8-H), 4.25-3.94 (m, 4H, OCH2CH3), 3.54 (bs, 1H, 2-H), 2.13
(s, 3H, 3-Me), 1.74 (d, J ) 1.6 Hz, 3H, 9-Me), 1.46 (s, 3H, 7-Me),
1.36 (s, 3H, 6-Me), 1.11 (t, J ) 7.1 Hz, 3H, OCH2CH3), 1.01 (t,
J ) 7.1 Hz, 3H, OCH2CH3); 13C NMR (75 MHz, CDCl3) δ
190.79, 190.20, 169.98, 169.76, 165.54, 161.48, 159.76, 141.76,
138.55, 138.40, 137.55, 133.05, 132.46, 129.03, 128.64, 128.52,
128.45, 128.37, 113.43, 106.38, 64.38, 62.72, 60.87, 60.48,
56.82, 55.78, 22.08, 17.04, 15.54, 13.99, 13.83, 10.82; UV λmax
(MeOH) 316.0 (27 000), 258.5 nm (48 000); HRMS calcd for
C36H36O6 564.2510, found 564.2504.
Z-28: oil; IR (neat) 1669, 1599 cm-1 1H NMR (300 MHz,
;
CDCl3, assignments were assisted by 1H-1H COSY and
NOESY experiments) δ 7.96 (bd, J ) 8.4 Hz, 2H, ortho H of
COPh), 7.58 (bt, J ) 7.4 Hz, 1H, para H of COPh), 7.48 (bt, J
) 7.4 Hz, 2H, meta H of COPh), 6.85 (bs, 1H, dCHCOPh),
6.10 (q, J ) 1.5 Hz, 1H, 3-H), 3.77 (q, J ) 7.1 Hz, 2H,
OCH2CH3), 2.26 (bs, 3H, 2-Me), 2.13 (d, J ) 1.5 Hz, 3H, 4-Me),
0.90 (t, J ) 7.1 Hz, 3H, OCH2CH3); 13C NMR (75 MHz, CDCl3)
δ 193.82, 164.11, 158.43, 147.58, 139.75, 136.97, 133.30,
133.23, 129.36, 129.09, 128.64, 118.99, 59.55, 15.92, 13.78,
12.37; UV λmax (MeOH) 459.0 (200), 377.0 (300), 273.5 (4600),
235.5 nm (3800); HRMS calcd for C18H18O3 282.1255, found
282.1266. E-28: mp 84.4-85.3 °C (ethyl ether-hexane); IR
Ack n ow led gm en t. We are grateful to the Material
Analytical Research Center of National Institute of
Materials and Chemical Research for NMR spectra,
HRMS spectra, and microanalyses.
(Nujol) 1665, 1593 cm-1 1H NMR (300 MHz, CDCl3 assign-
;
ments were assisted by 1H-1H COSY and NOESY experi-
ments) δ 8.13 (bs, 1H, dCHCOPh), 8.02 (bd, J ) 8.4 Hz, 2H,
ortho H of COPh), 7.62 (bt, J ) 7.4 Hz, 1H, para H of COPh),
7.49 (bt, J ) 7.4 Hz, 2H, meta H of COPh), 6.05 (q, J ) 1.5
Hz, 1H, 3-H), 4.30 (q, J ) 7.1 Hz, 2H, OCH2CH3), 2.35 (bs,
3H, 2-Me), 1.84 (3H, d, J ) 1.5 Hz, 4-Me), 1.37 (3H, t, J ) 7.1
Hz, OCH2CH3); 13C NMR (75 MHz, CDCl3) δ 195.56, 164.59,
157.63, 146.29, 138.69, 136.52, 136.38, 135.44, 134.00, 129.27,
128.84, 118.96, 59.69, 16.77, 15.75, 14.49; UV λmax (MeOH)
458.0 (600), 392.5 (900), 276.5 (13 200), 237.0 nm (11 900).
Su p p or tin g In for m a tion Ava ila ble: 1H and 13C NMR
spectra (31 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
J O970594X