Synthesis of benzofulvenes by palladium-catalyzed cyclization of 1,2-dialkynylbenzenes

Article abstract of DOI:10.1002/ejoc.200601029

A palladium-catalyzed cyclization of enediynes for the synthesis of benzofulvenes 2 in yields of 59-76% was accomplished by treatment of dialkynylbenzenes 1 with 5 mol% of PdX₂ and 3 equiv. of CuX ₂ in acetonitrile at 60 °C for 2 h.

Full text of DOI:10.1002/ejoc.200601029

FULL PAPER
DOI: 10.1002/ejoc.200601029
Synthesis of Benzofulvenes by Palladium-Catalyzed Cyclization of
1,2-Dialkynylbenzenes
Chia-Ying Lee[a] and Ming-Jung Wu*[a]
Keywords: Benzofulvenes / Palladium / Cyclization / Enediynes
A palladium-catalyzed cyclization of enediynes for the syn-
thesis of benzofulvenes 2 in yields of 59–76% was ac-
complished by treatment of dialkynylbenzenes 1 with 5 mol-
% of PdX2 and 3 equiv. of CuX2 in acetonitrile at 60 °C for
2 h.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
ures 1 and 2, respectively.[12] Upon treatment of 1a with
PdBr2 and CuBr2 under the same reaction conditions, com-
pound 4a was obtained in 95% yield. The spectroscopic
data of 4a are identical to those reported in the literature[13]
and elemental analysis confirmed the structure formula. Be-
cause there is a report suggesting that compounds such as
2a may be useful for the synthesis of fullerenes,[13] we ex-
plored this reaction as a general method for the preparation
of benzofulvenes. Thus, extension of this palladium-cata-
lyzed cyclization reaction to 1,2-dialkynylbenzenes 1b and
1c was carried out. Treatment of 1b with PdCl2 and CuCl2
gave 2b in 56% yield as a 4:1 mixture of stereoisomers and
3b in 23% yield. Reaction of 1b with PdBr2 and CuBr2 pro-
duced 4b in 83% yield as a 5:1 mixture of stereoisomers
and 3b in 12% yield. Similar results were obtained by the
reaction of 1c with either PdCl2 or PdBr2 under the same
reaction conditions to produce 2c and 3c in 42% and 87%
yields, respectively, along with 3b in 13% and 11% yields,
respectively (Table 1). From the above results, we can con-
clude that the use of 5 mol-% of PdBr2 and 3 equiv. of
Introduction
The Bergman cyclization of enediynes to generate 1,4-
dehydrobenzene biradicals has attracted much attention
during the past two decades[1] because biradical intermedi-
ates are reported to be the key species of enediyne antibiot-
ics that cause DNA damage.[2] More recently, the Bergman
cyclization was applied to prepare a variety of π-conjugated
materials.[3] In addition to the well-known thermally in-
duced cyclization reaction of enediynes, several nonclassical
Bergman-type cyclization reactions of enediynes initiated
by either electrophiles,[4] nucleophiles,[5] radicals,[6] or orga-
nometallics[7] have been reported. The palladium-catalyzed
reactions provide many unique organic transformations, es-
pecially for alkenes and alkynes.[8] To date, no report has
mentioned the palladium-catalyzed cyclization reaction of
enediynes; thus, we report herein the first examples of this
reaction to afford benzofulvenes.
Result and Discussion
The PdX2 and CuX2 catalyst system was successfully em-
ployed in the carbonylation[9] and cyclotrimerization[10] of
alkynes. We therefore treated 1,2-bis(2-phenylethynyl)ben-
zene (1a) with 5 mol-% of PdCl2 and 3 equiv. of CuCl2 in
acetonitrile at 60 °C for 2 h. Indene 2a was obtained in 75%
yield as a 4:1 mixture of (E/Z) isomers along with 21%
yield of product 3a.[11] The X-ray crystal structures of the
major isomer of 2a and compound 3a are shown in Fig-
[a] Faculty of Medicinal and Applied Chemistry, Kaohsiung Medi-
cal University,
Kaohsiung, Taiwan
Fax: +886-7-3125339
E-mail: mijuwu@cc.kmu.edu.tw
Figure 1. ORTEP plots for X-ray crystal structure of 2a.
Eur. J. Org. Chem. 2007, 3463–3467
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C.-Y. Lee, M.-J. Wu
FULL PAPER
CuBr2 gives the benzofulvenes in better yields and higher
When compound 1a was treated with PdCl2 and CuCl2
stereoselectivities; additionally, indenone 3b always appear under the same reaction conditions except with the use of
as a byproduct in these reactions.
methanol as the solvent, three products were obtained. The
major product obtained in 53% yield was assigned as com-
pound 6a as a 4:1 mixture of (E/Z) isomers. Fractional
crystallization gave crystals of (E)-6a[12] (Figure 3). Com-
pounds 2a and 3a were isolated in 8% and 15% yields,
respectively. The reaction was also performed with ethanol
as the solvent and compounds 6b, 2a, and 3a were obtained
in 45, 15, and 16% yields, respectively. This reaction can
also be carried out by using CH3CN as the solvent contain-
ing 10 equiv. of methanol, which affords compound 6a in
75% yield as a 3:1 mixture of (E/Z) isomers. Instead of
methanol, ethanol and 2-propanol were added into the re-
action mixture, respectively. The yield of compound 2a in-
creased as the nucleophilicity of the additive decreased
(Table 2). We also introduced other nucleophilic additives
into the reaction mixture, such as HOAc, PhOH, and
NaCN. However, only compound 2a was obtained without
Figure 2. ORTEP plots for X-ray crystal structure of 3a.
Table 1. Reaction of 1a–c with PdX2 and CuX2 catalysts.
Product yields [%]
1a, Ar = Ph
X = Cl
X = Br
2a (75)
4a (95)
2b (56)
4b (42)
2c (83)
4c (87)
3a (21)
1b, Ar = 4-CH3OC6H4 X = Cl
3b (23)
3b (13)
3c (14)
3c (11)
X = Br
X = Cl
X = Br
1c, Ar = 4-CF3C6H4
Figure 3. ORTEP plots for X-ray crystal structure of 6a.
1,2-Bis(1-hexynyl)benzene (1d) bearing an alkyl group on
the alkyne terminus was examined in the cyclization reac-
tion. Treatment of 1d with PdCl2 and CuCl2 under the de-
scribed reaction conditions gave 2d in 59% yield as a 6:1
mixture of stereoisomers. Surprisingly, when the reaction of
1d with PdBr2 and CuBr2 was carried out, fulvene 4d was
obtained in only 27% yield. The major product was ob-
tained in 45% yield and the structure was assigned as com-
pound 5d [Equation (1)]. The less electron-stabilizing sub-
stituent, that is the alkyl group, may slow down the cycliza-
tion step; thus, the bromine addition adduct turns out to
be the major product.
Table 2. Nucleophile effect on the synthesis of 1-chloro-3-[(chlo-
ro)(phenyl)methylene]-2-phenylindene (2a).
Solvent
CH3OH none
EtOH none
Additive
Product yields [%]
2a (5)
R = OCH3 6a (53) 3a (12)
2a (15) R = OEt
6b (45) 3a (16)
CH3CN CH3OH (10 equiv.) 2a (8)
CH3CN EtOH (10 equiv.)
CH3CN iPrOH (10 equiv.) 2a (22) R = OiPr
R = OCH3 6a (75) 3a (15)
2a (28) R = OEt
6b (44) 3a (23)
6c (50) 3a (18)
3a (33)
CH3CN H2O (10 equiv.)
2a (61)
(1)
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Benzofulvenes by Pd-Catalyzed Cyclization of Disubstituted Benzenes
FULL PAPER
nucleophile-cooperated product 6. The introduction of pound 4a was treated with phenylboronic acid under Su-
10 equiv. of H2O into the reaction mixture gave 2a in 61% zuki coupling reaction conditions to give 12 in 40% yield
yield and 3a in 33% yield.
[Equation (3)].
A plausible mechanism for the formation of compounds
2a and 6a is proposed in Scheme 1. First, PdCl2 undergoes
addition to the alkyne to give intermediate 7a, followed by
vinylpalladium isomerization to give 7. Intermediate 7 can
then undergo 5-exo-dig cyclization to form 8. Intermediate
8 then undergoes reductive elimination to give 2a and palla-
dium(0), which could be oxidized by CuCl2 to regenerate
PdCl2. In the presence of methanol, the chloride ligand of
8 can be replaced to give 9, which then undergoes reductive
elimination to form compound 6a.
(3)
Conclusions
We developed a general method for the synthesis of di-
halobenzofulvenes. These products can be converted to a
variety of substituted benzofulvenes. We also found that
palladium-catalyzed cyclization of enediynes proceeds in
the exo–endo mode to give the fulvenes instead of Bergman
cyclization to give a benzene ring.
Experimental Section
General Procedure for the Cyclization of 1,2-Dialkynylbenzenes: To
a stirred solution of 1,2-dialkynylbenzene (1 mmol) in 10 mL of
CH3CN was added PdCl2 (0.05 mmol) and CuCl2 (2 mmol), the
solution was heated to 60 °C and stirred for 4 h. After cooling to
room temperature, a saturated aqueous solution of NaCl was
added into the reaction mixture and extracted with EtOAc. The
combined organic extracts were dried with anhydrous MgSO4(s).
After filtration and removal of solvent, the residue was purified by
column chromatography to give the products.
(E)-1-Chloro-3-[(chloro)(phenyl)methylene]-2-phenylindene (2a): Ob-
tained as a yellow solid, m.p. 123–124 °C. 1H NMR (400 MHz,
CDCl3): δ = 8.60 (d, J = 7.6 Hz, 1 H), 7.52 (d, J = 8.0 Hz, 1 H),
7.48–7.40 (m, 2 H), 7.13 (dt, J = 8.0, 1.2 Hz, 2 H), 7.03–6.90 (m,
8 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 139.6, 139.1, 138.4,
136.1, 134.9, 134.8, 134.3, 133.7, 130.4 (2 C), 130.1 (2 C), 128.9,
128.7, 128.6, 127.4, 127.2 (3 C), 125.1, 119.2 ppm. C22H14Cl2
(349.2526): calcd. C 75.66, H 4.04; found C 75.53, H 4.00.
Scheme 1.
(E)-1-Chloro-3-[(chloro)(4-methoxyphenyl)methylene]-2-(4-meth-
oxyphenyl)indene (2b): Obtained as a yellow solid, m.p. 147–
148 °C.1H NMR (400 MHz, CDCl3): δ = 8.56 (d, J = 7.6 Hz, 1 H),
7.49–7.36 (m, 3 H), 7.04 (d, J = 8.8 Hz, 2 H), 6.84 (d, J = 8.8 Hz,
2 H), 6.51 (d, J = 8.8 Hz, 2 H), 6.43 (d, J = 8.8 Hz, 2 H), 3.69 (d,
J = 6.8 Hz, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 160.1,
157.9, 139.5, 139.2, 135.8, 134.9, 134.3, 133.2 132.1 (2 C), 131.3 (2
C), 130.8, 128.3, 127.1, 126.2, 124.8, 118.9, 112.9 (2 C), 112.7 (2
C), 55.2, 55.1 ppm. C24H18Cl2O2 (409.3045): calcd. C 70.43, H 4.43;
found C 70.25, H 4.43.
(Z)-1,6-Diphenyl-3-hexen-1,5-diyne (10) was also used in
this reaction. Treatment of 10 with 5 mol-% of Pd(PPh3)4
and 3 equiv. of CuCl2 under the described reaction condi-
tions gave compound 11 in only 25% yield [Equation (2)].
This reaction is not very clean, and compound 11 is the
product obtained after further reaction of the initially
formed dichlorofulvene with CuCl2. To explore the syn-
thetic utility of these intermediary fulvene products, com-
(Z)-1-Chloro-3-[(chloro)(4-methoxyphenyl)methylene]-2-(4-meth-
oxyphenyl)indene (2b): Obtained as a yellow solid, m.p. 137–
138 °C.1H NMR (400 MHz, CDCl3): δ = 7.45–7.23 (m, 5 H), 7.24
(t, J = 7.6 Hz, 1 H), 7.00–6.97 (m, 4 H), 6.94 (t, J = 7.6 Hz, 1 H),
6.42 (d, J = 8.0 Hz, 1 H), 3.89 (d, J = 11.6 Hz, 6 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 160.9, 159.1, 138.7, 137.8, 136.5,
135.5, 134.6, 134.4 132.2, 131.1 (2 C), 130.9 (2 C), 127.6, 127.3,
(2) 126.3, 122.7, 118.8, 114.3 (2 C), 113.5 (2 C), 55.4, 55.2 ppm.
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C.-Y. Lee, M.-J. Wu
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C24H18Cl2O2 (409.3045): calcd. C 70.43, H 4.43; found C 70.44, H
4.54.
(E)-1-Bromo-3-[(bromo)(4-methoxyphenyl)methylene]-2-(4-meth-
oxyphenyl)indene (4b): Obtained as a yellow solid, m.p. 139–140 °C.
1H NMR (400 MHz, CDCl3): δ = 8.76 (d, J = 7.6 Hz, 1 H), 7.46–
7.31 (m, 3 H), 7.03–6.99 (m, 2 H), 6.81 (td, J = 8.8, 2.4 Hz, 2 H),
6.50 (dd, J = 8.4, 2.0 Hz, 2 H), 6.41 (dd, J = 8.4, 3.2 Hz, 2 H), 3.71
(s, 3 H), 3.68 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
159.8, 157.9, 141.1, 139.5, 137.5, 135.7, 134.9, 133.3 132.2 (2 C),
131.3, 131.2, 131.1, 130.7, 128.6, 127.4, 126.7, 124.4, 122.7, 120.6,
112.8, 112.6 55.2, 55.1 ppm. C24H18Br2O2 (498.2065): calcd. C
57.86, H 3.64; found C 57.85, H 3.59.
(E)-1-Chloro-3-[(chloro)(4-trifluoromethylphenyl)methylene]-2-(4-tri-
fluoromethylphenyl)indene (2c): Obtained as a yellow solid, m.p.
152–153 °C. 1H NMR (400 MHz, CDCl3): δ = 8.56 (d, J = 8.0 Hz,
1 H), 7.53–7.43 (m, 4 H), 7.27–7.17 (m, 5 H), 7.00 (d, J = 8.0 Hz,
2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 141.5, 139.3, 137.3,
136.1, 134.5, 134.0, 131.8, 130.6 (3 C), 130.4 (3 C), 129.5, 129.3,
128.1, 127.2, 125.3, 124.3 (2 C), 124.2 (3 C), 119.7 ppm.
C24H12Cl2F2 (485.2486): calcd. C 59.40, H 2.49; found C 59.44, H
2.63.
(Z)-1-Bromo-3-[(bromo)(4-methoxyphenyl)methylene]-2-(4-meth-
oxyphenyl)indene (4b): Obtained as a yellow solid, m.p. 157–158 °C.
1H NMR (200 MHz, CDCl3): δ = 7.41–7.18 (m, 6 H), 7.03–6.87
(m, 5 H), 6.27 (d, J = 7.6 Hz, 1 H), 3.88 (d, J = 4.6 Hz, 6 H) ppm.
13C NMR (50 MHz, CDCl3): δ = 160.7, 159.3, 140.9, 140.5, 139.8,
137.7, 135.0, 134.6 131.4 (2 C), 130.6 (2 C), 130.3, 129.3, 128.2,
127.4, 126.5, 122.8, 121.1, 119.9, 114.3, 113.6, 55.4, 55.2 ppm.
(Z)-1-Chloro-3-[(chloro)(4-trifluoromethylphenyl)methylene]-2-(4-tri-
fluoromethylphenyl)indene (2c): Obtained as a yellow solid. 1H
NMR (400 MHz, CDCl3): δ = 8.56 (d, J = 8.0 Hz, 1 H), 7.53–7.43
(m, 4 H), 7.27–7.17 (m, 5 H), 7.00 (d, J = 8.0 Hz, 2 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 142.9, 138.8, 138.7, 137.7, 135.3,
135.0, 131.8, 130.4 (2 C), 129.5 (3 C), 128.4, 127.2, 126.3, 126.2 (2
C), 126.1, 125.2, 125.1 (2 C), 125.0, 122.7, 119.5ppm.
(E)-1-Bromo-3-[(bromo)(4-trifluorophenyl)methylene]-2-(4-trifluoro-
methylphenyl)indene (4c): Obtained as a yellow solid, m.p. 177–
178 °C. 1H NMR (200 MHz, CDCl3): δ = 8.74 (dt, J = 6.8, 1.4 Hz,
1 H), 7.64 (s, 1 H), 7.52–7.42 (m, 3 H), 7.24–7.16 (m, 5 H), 7.06
(d, J = 8.0 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 143.9,
140.9, 139.1, 138.6, 137.8, 135.2, 132.5, 131.7, 130.5 (6 C), 129.5 (2
C), 127.8, 124.8, 124.3 (2 C), 124.2 (3 C), 121.2 ppm. C24H12Br2F6
(574.1505): calcd. C 50.21, H 2.11; found C 50.17, H 2.36.
(E)-2-Butyl-1-chloro-3-[(chloro)(butyl)methylene]indene (2d): Ob-
1
tained as a yellow oil. H NMR (400 MHz, CDCl3): δ = 7.53 (d, J
= 7.6 Hz, 1 H), 7.38–7.22 (m, 3 H), 3.09 (t, J = 8.0 Hz, 2 H), 1.88–
1.80 (m, 2 H), 1.64–1.44 (m, 6 H), 1.07–0.98 (m, 6 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 142.0, 139.4, 137.5, 133.8, 133.6,
133.1, 127.4, 125.9, 122.6, 118.4, 40.4, 31.5, 29.8, 27.6, 22.8, 22.5,
13.9, 13.8 ppm. HRMS (EI): calcd. for C18H22Cl2 308.1099; found
308.1092.
(Z)-1-Bromo-3-[(bromo)(4-trifluorophenyl)methylene]-2-(4-trifluoro-
methylphenyl)indene (4c): Obtained as a yellow solid, m.p. 171–
172 °C. 1H NMR (400 MHz, CDCl3): δ = 7.78–7.71 (m, 4 H), 7.58–
7.53 (m, 4 H), 7.39 (dt, J = 7.6, 0.8 Hz, 1 H), 7.29 (t, J = 7.6 Hz,
1 H), 6.94 (td, J = 7.6, 0.8 Hz, 1 H), 6.08 (d, J = 7.6 Hz, 1 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 145.3, 145.2, 139.8, 139.7, 139.0,
138.4, 134.3, 130.7 (2 C), 129.1 (2 C), 128.5, 127.3, 126.3, 126.2 (2
C), 126.1, 125.9, 125.3, 125.2 (2 C), 125.1, 122.8, 120.7 ppm.
3-Benzoyl-2-phenylindenone (3a): Obtained as an orange solid, m.p.
125–126 °C. 1H NMR (400 MHz, CDCl3): δ = 7.92 (d, J = 8.0 Hz,
2 H), 7.21 (d, J = 7.2 Hz, 1 H), 7.51 (d, J = 7.6 Hz, 1 H), 7.49–
7.20 (m, 9 H), 7.04 (d, J = 7.2 Hz, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 196.0, 194.6, 150.4, 144.0, 135.1, 134.4, 134.3, 129.6,
129.5, 129.3 (6 C), 128.9, 128.8 (2 C), 128.3 (2 C), 123.9, 121.7 ppm.
C22H14O2 (310.3454): calcd. C 85.14, H 4.55; found C 85.04, H
4.59.
(E)-1-Bromo-3-[(bromo)(butyl)methylene]-2-butylindene (4d): Ob-
tained as a yellow oil. 1H NMR (200 MHz, CDCl3): δ = 7.50 (d, J
= 7.6 Hz, 1 H), 7.34–7.17 (m, 3 H), 3.29 (t, J = 8.0 Hz, 2 H), 2.98
(t, J = 8.0 Hz, 2 H), 1.88–1.81 (m, 2 H), 1.79–1.40 (m, 6 H), 1.07–
0.95 (m, 6 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 140.8, 140.4,
136.6, 134.8, 134.4, 127.6, 126.1, 125.7, 122.8, 119.4, 43.4, 31.6,
30.1, 29.1, 22.9, 22.4, 13.9, 13.8 ppm. HRMS (EI): calcd. for
C18H22Br2 396.0088; found 396.0081.
3-(4-Methoxybenzyl)-2-(4-methoxyphenyl)indenone (3b): Obtained
as an orange solid, m.p. 116–117 °C. 1H NMR (400 MHz, CDCl3):
δ = 7.91 (d, J = 9.2 Hz, 2 H), 7.57 (d, J = 6.8 Hz, 1 H), 7.42 (d, J
= 8.8 Hz, 2 H), 7.33 (t, J = 8.0 Hz, 1 H), 7.24 (t, J = 8.0 Hz, 1 H),
6.96 (d, J = 7.2 Hz, 1 H), 6.83 (d, J = 8.8 Hz, 2 H), 6.77 (d, J =
8.8 Hz, 2 H), 3.81 (s, 3 H), 3.74 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 196.0, 194.6, 150.4, 144.0, 135.1, 134.4, 134.3, 129.6,
129.5, 129.3 (6 C), 128.9, 128.8 (2 C), 128.3 (2 C), 123.9, 121.7 ppm.
C24H18O4 (370.3973): calcd. C 80.11, H 4.97; found C 79.22, H
4.97.
1-[(E)-1,2-Dibromohexen-1-yl]-2-(hexyn-1-yl)benzene (5d): Obtained
as a yellow oil. 1H NMR (400 MHz, CDCl3): δ = 7.44 (d, J =
7.2 Hz, 1 H), 7.33–7.19 (m, 3 H), 2.98–2.74 (m, 2 H), 2.42 (t, J =
6.6 Hz, 2 H), 1.76–1.41 (m, 8 H), 1.28–0.93 (m, 6 H) ppm. 13C
NMR (50 MHz, CDCl3): δ = 142.9, 132.3, 128.7, 128.3, 127.6,
125.1, 123.1, 115.1, 94.9, 78.2, 39.9, 30.6, 29.7, 21.9, 21.7, 19.3,
14.0, 13.6 ppm. HRMS (EI): calcd. for C18H22Br2 396.0088; found
396.0091.
3-(4-Trifloromethylbenzyl)-2-(4-trifluoromethylphenyl)indenone (3c):
Obtained as a orange solid, m.p. 181–182 °C. 1H NMR (400 MHz,
CDCl3): δ = 8.01 (d, J = 8.0 Hz, 2 H), 7.68–7.63 (m, 3 H), 7.50 (s,
4 H), 7.45–7.35 (m, 2 H), 7.0.7 (d, J = 7.6 Hz, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 194.9, 193.2, 151.0, 143.2, 134.7, 132.8,
130.2, 129.6 (6 C), 129.2, 126.1 (2 C), 126.0, 125.9, 125.4 (2 C),
125.3 (2 C), 124.4, 122.2 ppm. C24H12F6O2 (446.3413): calcd. C
64.29, H 3.15; found C 63.99, H 3.01.
1-Chloro-3-[(methoxy)(phenyl)methylene]-2-phenylindene (6a): Ob-
tained as a yellow solid and a 4:1 mixture of (E) and (Z) isomers,
m.p. 111–112 °C. 1H NMR (400 MHz, CDCl3): δ = 8.22 (d, J =
6.8 Hz, 0.8 H), 7.53–7.33 (m, 7 H), 7.05–6.86 (m, 12 H), 6.19 (d, J
= 7.8 Hz, 0.2 H), 3.62 (s, 2.4 H), 3.11 (s, 0.6 H) ppm. 13C NMR
(100 MHz, CDCl3) for (E) isomer: δ = 162.4, 137.8, 135.6, 134.5,
131.7, 130.5, 129.8, 129.5, 129.2, 129.1, 127.5 (3 C), 127.4, 126.9
(3 C), 26.3, 126.1, 123.9, 118.5, 57.4 ppm. HRMS (EI): calcd. for
C23H17ClO 344.0968; found 344.0965. C23H17ClO (344.8335):
calcd. C 80.11, H 4.97; found C 79.22, H 4.97.
(E)-1-Bromo-3-[(bromo)(phenyl)methylene]-2-phenylindene (4a): Ob-
tained as a yellow solid, m.p. 141–142 °C. 1H NMR (200 MHz,
CDCl3): δ = 8.83 (d, J = 7.8 Hz, 1 H), 7.54–7.39 (m, 3 H), 7.14–7.01
(m, 2 H), 6.99–6.88 (m, 8 H) ppm. 13C NMR (50 MHz, CDCl3): δ
= 141.1, 140.7, 139.8, 138.1, 135.6, 134.9, 130.4 (2 C), 130.1 (2 C),
128.9, 128.7, 127.2 (3 C), 127.1 (3 C), 127.0, 126.5, 124.5,
120.7 ppm. C22H14Br2 (438.1546): calcd. C 60.31, H 3.22; found C
60.33, H 3.14.
1-Chloro-3-[(ethoxy)(phenyl)methylene]-2-phenylindene (6b): Ob-
tained as a yellow solid and a 3:1 mixture of (E) and (Z) isomers,
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Eur. J. Org. Chem. 2007, 3463–3467

Benzofulvenes by Pd-Catalyzed Cyclization of Disubstituted Benzenes
FULL PAPER
m.p. 147–148 °C. 1H NMR (400 MHz, CDCl3): δ = 8.35 (d, J =
6.4 Hz, 0.7 H), 7.58–7.36 (m, 7 H), 7.19 (t, J = 7.2 Hz, 0.5 H),
7.08–7.05 (m, 3 H), 6.98–6.86 (m, 7 H), 6.16 (d, J = 7.8 Hz, 0.3
H), 3.88 (q, J = 7.6 Hz, 1.5 H), 3.40 (q, J = 7.6 Hz, 0.5 H), 1.39
(t, J = 7.6 Hz, 2.25 H), 0.65 (t, J = 7.6 Hz, 0.75 H) ppm. 13C NMR
(100 MHz, CDCl3) for (E) isomer: δ = 161.8, 137.8, 135.6, 134.6,
134.5, 132.1, 130.4 (2 C), 130.1 (2 C), 129.6, 129.1 (2 C), 127.4 (2
C), 126.9 (2 C), 126.4, 126.2, 123.9, 121.1, 118.4, 66.1, 15.5 ppm.
C24H19ClO (358.8601): calcd. C 80.33, H 5.34; found C 80.07, H
5.30.
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70, 2568.
1-Chloro-3-[(isopropoxy)(phenyl)methylene]-2-phenylindene (6c):
Obtained as a yellow solid and a 9:1 mixture of (E) and (Z) iso-
1
mers, m.p. 186–187 °C. H NMR (400 MHz, CDCl3): δ = 8.41 (d,
J = 5.6 Hz, 0.9 H), 7.53–7.39 (m, 1 H), 7.37–7.34 (m, 2 H), 7.08–
7.05 (m, 3 H), 6.97–6.87 (m, 7 H), 6.10 (d, J = 7.8 Hz, 0.1 H), 4.23
(sept, J = 6.4 Hz, 1 H), 3.89 (sept, J = 6.4 Hz, 0.1 H), 1.32 (d, J =
6.0 Hz, 5.4 H), 0.71 (d, J = 6.0 Hz, 0.6 H) ppm. 13C NMR
(100 MHz, CDCl3) for (E) isomer: δ = 161.2, 137.9, 135.7, 134.8,
132.5, 130.4 (2 C), 130.1 (2 C), 129.7, 128.9, 127.4 (2 C), 127.2,
126.9 (2 C), 126.4, 126.2, 125.9, 124.0, 121.7, 118.4, 72.7, 27.6 (2
C) ppm. C25H21ClO (372.8866): calcd. C 80.53, H 5.60; found C
80.43, H 5.71.
(Z)-[Chloro(3,4,5-trichloro-2-phenylcyclopent-2-enylidene)methyl]-
1
benzene (11): Obtained as a pale yellow oil. H NMR (200 MHz,
CDCl3): δ = 7.52–7.28 (m, 4 H), 7.04–6.82 (m, 6 H), 5.34 (s, 1 H),
4.93 (s, 1 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 140.2, 136.8,
136.4, 135.8, 134.3, 131.4, 129.3, 128.9, 128.3, 128.1, 127.5, 127.2,
68.6, 64.1 ppm. HRMS (EI): calcd. for C18H12Cl4 367.9693; found
367.9695.
1-Benzhydrylidene-2,3-diphenylindene (12): Obtained as a yellow so-
lid, m.p. 233–234 °C (ref.[14] 232 °C). 1H NMR (400 MHz, CDCl3):
δ = 7.48–7.40 (m, 4 H), 7.28–7.11 (m, 8 H), 6.91–6.75 (m, 11 H),
6.42 (dt, J = 7.6, 1.2 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 149.5, 143.6, 143.5, 142.9, 141.2, 138.9, 138.1, 137.5, 136.4,
135.2, 132.1, 130.9, 130.7, 129.8, 128.6 (2 C), 127.8, 127.6, 126.8 (2
C), 125.2, 125.0, 123.4, 119.7 ppm. MS(EI): m/z (%) = 432 (100)
[M]+. C34H24 (432.5544): calcd. C 94.41, H 5.59; found C 93.82, H
5.56.
[11] D. Ramkumar, M. Kalpana, B. Varghese, S. Sankararaman,
M. N. Jagadeesh, J. Chandrasehhar, J. Org. Chem. 1996, 61,
2247.
[12] For 2a: CCDC-623067 [cell parameters: a = 8.7380(2), b =
9.1320(2), c = 12.1690(3)]; for 3a: CCDC-623068 [cell param-
eters: a = 8.4997(11), b = 10.0925(13), c = 19.635(3)]; for 6a:
CCDC-623069 [cell parameters: a = 9.4463(9), b = 12.0564(11),
c = 17.1862(16)] contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgments
[13] P. R. Schreiner, M. Prall, V. Lutz, Angew. Chem. Int. Ed. 2003,
42, 5757.
We thank the National Science Council of the Republic of China
for financial support of this program.
[14] G. Dyker, S. Borowski, G. Henkel, A. Kellner, I. Dix, P. Jones,
Tetrahedron Lett. 2000, 41, 8259
Received: November 29, 2006
Published Online: May 25, 2007
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Eur. J. Org. Chem. 2007, 3463–3467
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