Synthesis of benzocyclobutadiene trimers and all-Z-tribenzo[12]annulene. A new family of concave π-systems

Article abstract of DOI:10.1016/S0040-4020(01)00244-7

Nickel-catalyzed oligomerization of trans-1,2-dibromobenzocyclobutene formed cyclic dimers and trimers. Upon heating, the major anti-cyclic trimer afforded a cage compound, whereas the minor syn-trimer produced all-Z-tribenzo[12]annulene. Dehydrogenation

Full text of DOI:10.1016/S0040-4020(01)00244-7

TETRAHEDRON
Pergamon
Tetrahedron 57 32001) 3567±3576
Synthesis of benzocyclobutadiene trimers and
all-Z-tribenzo[12]annulene. A new family of concave p-systems
Yoshiyuki Kuwatani,a Tadahiro Yoshida,a Ayako Kusaka,a Masaji Oda,b Kenji Hara,a
Masato Yoshida,a Haruo Matsuyamaa and Masahiko Iyodaa,p
aDepartment of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
bDepartment of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
Received 25 September 2000; accepted 2 December 2000
AbstractÐNickel-catalyzed oligomerization of trans-1,2-dibromobenzocyclobutene formed cyclic dimers and trimers. Upon heating, the
major anti-cyclic trimer afforded a cage compound, whereas the minor syn-trimer produced all-Z-tribenzo[12]annulene. Dehydrogenation of
the anti-trimer with DDQ resulted in the formation of an indenoazulene derivative, and a similar reaction of the syn-trimer yielded a bowl-
shaped system. All-Z-tribenzo[12]annulene was also synthesized using a stepwise route starting from o-diiodobenzene and o-ethynylbenzyl
alcohol, the overall yield being 22%. All-Z-tribenzo[12]annulene behaved like p-prismand and formed chromium30) tricarbonyl and silver3I)
complexes. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
Recently, we developed a simple and ef®cient method for
the nickel-catalyzed cyclooligomerization of ole®ns and
acetylenes.6,7 Since our method produced cyclic trimers
predominantly in some cases, we expected that the reaction
of 1 with a nickel30) catalyst could lead to the formation of
the cyclic trimers 36a and 6b) 3Scheme 2). The cyclic
trimers 36a and 6b) can be regarded as a precursor of
threefold-symmetric [4]phenylene 7.8 In addition, all-Z-
tribenzo[12]annulene 38) with C3v p-cavity was presumed
to be obtained by the thermal ring-cleavage of all-syn-trimer
6b.9 A combination of the benzene rings and ethylenic
bonds in 6 and 8 forms a concavity, and hence these
molecules like `p-prismand' might play an important role
as a host molecule for metal ions 39 and 10 in Scheme 2).10
In order to examine the novel host properties of 8, we also
developed a new synthetic route to 8 starting from o-di-
iodobenzene 311) and o-ethynylbenzyl alcohol 312).
Benzocyclobutadiene 32), which can be generated by the
reduction of trans-1,2-dibromobenzocyclobutene 31), is a
very unstable molecule,1 and easily dimerizes to produce
the so-called `angular dimer' 33) 3Scheme 1).2,3 In contrast,
the reaction of 2 with transition metals forms stable benzo-
cyclobutadiene±metal complexes 34).4 In the case of the
reaction of 1 with Ni3CO)4, the formation of the `linear
dimer' 35) via 4 [MˆNi3CO)2] was reported.5
H
Zn
H
2
3
Br
Br
In a preliminary form, we reported the nickel-catalyzed
cyclooligomerization of benzocyclobutadiene 32) and the
synthesis and properties of all-Z-tribenzo[12]annulene
38).11 In this paper, we describe the syntheses and properties
of 6a, 6b, and 8 in detail, together with an attempted
synthesis of 7 by aromatization of 6a and 6b.
M
4
1
Ni(CO)4
5
2. Results and discussion
Scheme 1. Reactions of 1 via 2.
2.1. Cyclooligomerization of 1 with Ni*0) complexes
Keywords: annulenes; cage compounds; complexation; nickel and
compounds; oligomerization; ring transformations.
Corresponding author. Tel.: 181-426-77-2547; fax: 181-426-77-2525;
e-mail: iyoda-masahiko@c.metro-u.ac.jp
Although a number of cyclooligomerization methods of
ole®ns and acetylenes have been reported up to now,12
only limited reactions can be employed for selective
p
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020301)00244-7

3568
Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
Br
Br
•
•
•
•
[Ni(0)]
•
•
•
•
+
?
•
•
1
7
6a
6b
∆
M
I
I
CH2OH
+
M
11
12
8
10
9
Scheme 2. Cyclic trimerization of 1 with Ni30) and synthesis of 8.
•
Br
•
NiBr2L2, Zn
•
•
•
5a
•
•
•
•
+
+
+
Additive
Br
• •
•
•
•
1
13
• •
L: PPh3 or PBun
3
5b
6a
6b
Scheme 3. Reaction of 1 with Ni30) complexes.
cyclodimerization and cyclotrimerization of unsaturated
molecules.6,13 A well known example is the reaction of
strained 3,3-dimethylcyclopropene with nickel30) and palla-
dium30) complexes,13 which yields the cyclic dimer and
trimer, respectively, in good yields. Another example is
the reaction of butatrienes with nickel30) complexes,
which produces the corresponding cyclic dimer 3[4]radia-
lenes) in THF and the cyclic trimer 3[6]radialenes) in DMF,
respectively.6 Bearing these results in mind, we tried the
reactions of 1 with nickel30) complexes 3Scheme 3) and
we expected the cyclodimerization in THF and the cyclo-
trimerization in DMF. A typical procedure involved treat-
ment of 1 31 equiv.) at room temperature with a nickel30)
complex which was generated in situ by reduction of
NiBr2L2 3LˆPPh3 or PBu3) 30.2 equiv.) with activated
zinc dust 34 equiv.) in the presence of a ligand 3PPh3 or
of the dimers 5 344%) and the trimers 6 321%). In contrast to
the results in THF, the reaction of 1 with Ni3PPh3)4 in DMF
formed predominantly the trimers 6 in 42% total yield with
a small amount of dimers 5 3entry 5). The same treatment of
1 with Ni3PBun ) in DMF afforded a similar result 3entry 8),
3 4
although the reaction of 1 with Ni3PBun ) in THF gave a
3 4
rather poor result 3entry 4). The formation of dibenzo[a,e]-
cyclooctene 313) in entries 2 and 4±8 may be due to the
nickel-catalyzed ring-opening of the dimers 5. The reactions
of Ni30) complexes in the presence of an iodide ion in DMF
also resulted in the predominant formation of the trimers 6
Table 1. Reaction of trans-1,2-dibromobenzocyclobutene 31) with
nickel30) complexesa
Entry
L
Additive Solvent
Yields 3%)b
PBun , 0.4 equiv.) or an iodide 3Et4NI or NaI, 2 equiv.) as
5
a
5
b
6a 6b
13
3
an additive 3see Table 1). The products obtained were the
anti- and syn-dimers 35a and 5b), the anti- and syn-trimers
36a and 6b), and dibenzo[a,e]cyclooctene 313), which were
isolated by column chromatography on silica gel. The
obtained dimer by the reaction of 1 with Ni3CO)4 was
found to be identical with the anti-isomer 35a) by the melt-
ing point determination.5
1c
2
3
4
5
6
7
8
PPh3 PPh3
PPh3 PPh3
PPh3 Et4NI
PBu3 PBu3
PPh3 PPh3
PPh3 Et4NI
PPh3 NaI
Benzene
THF
THF
0
0
18 Trace
0
7
21
5
0
0
4
0
8
1
2
2
2
1
0
0
4
31 13
THF
7
6
6
5
2
2
DMF
DMF
DMF
DMF
Trace 38
Trace 38 Trace
Trace 40
38
1
1
PBu3 PBu3
1
a
As shown in Table 1, the nickel-catalyzed cyclooligomer-
ization of 1 in benzene gave no detectable products and 83%
of the starting material was recovered 3entry 1). However,
similar reactions of 1 in THF produced mainly the dimers 5
with smaller amounts of the trimers 6 3entry 2). The
presence of an iodide ion in the reaction media 3entry 3)
accelerated the cyclooligomerization to increase the yields
A solution of trans-1,2-dibromobenzocyclobutene 31) 34 mmol) was
added over 2 h at room temperature to a suspension of the nickel30)
complex generated from NiBr2L2 30.8 mmol), zinc 316 mmol), and the
additive [PPh3 or PBun 31.6 mmol), or Et4NI or NaI 38 mmol)] in ben-
3
zene, THF, or DMF as solvent, and the resulting mixture was stirred at
room temperature for 15 h.
Isolated yield.
b
c
Starting material 1 was recovered 383%).

Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
3569
∆ or Ag+
5
NiL4
4
1
Ni
NiL2
13
L
L
L = PPh3
14
4
or PBun
4
3
∆
- NiL2
6a
+
5
16
[2+2+2]
17
- NiL2
6
Ni
L
L
15
18a
18b
Scheme 4. Plausible mechanism of the nickel-catalyzed cyclooligomeriza-
tion of 1.
∆
6b
+
3entries 6 and 7). Palladium complexes are often employed
for the dimerization and oligomerization of unsaturated
compounds.14 However, treatment of 1 with PdCl23PPh3)2
30.2 equiv.), Zn 34 equiv.), and PPh3 30.4 equiv.) in DMF at
room temperature afforded the dimers in very low yields
35a: 1.3% and 13: 1.6%). In addition, the reaction of 1
8
19
Scheme 5. Thermal ring-opening of 5 and 6.
Ê
squares plane of the central six-membered ring is 0.05 A.
It is worth noting that the Csp3 ZCsp3 bond lengths of the
central cyclohexane ring have a bond alternation. Thus,
the Csp3 ZCsp3 bond lengths fused by the benzocyclobutene
15
with CoCl3PPh3)3 32.4 equiv.) in benzene produced 5a
and 5b in 11% and 1% yields, respectively.
Ê
The mechanism for the cyclooligomerization of 1 can be
represented as shown in Scheme 4. The nickel-catalyzed
coupling of benzyl halides usually proceeds smoothly to
give the corresponding bibenzyls in good to high yields.16
However, the reaction of 1 with the Ni30) complex may ®rst
generate the benzocyclobutadiene complex 4 3MˆNiL2).
This assumption follows from the observation that the reac-
tion of 1 with Ni3PPh3)4 with benzene yielded neither the
dimers nor the trimers, although the nickel-catalyzed
coupling of benzyl halides proceeds smoothly in benzene
as the solvent. The predominant formation of the trimers 6
in DMF may be attributable to the stability of the nickel-
acyclopentane intermediate 14 which is more stabilized in
DMF and allowed to react with another molecule of 4.
ring are 1.59±1.60 A, which are slightly longer than that of
18
benzocyclobutene 30.02 A, averaged value), whereas the
Ê
Csp3 ZCsp3 bond lengths between the four-membered rings
Ê
are 1.52±1.54 A. The existence of this bond-alternation in
6a might be favorable for the thermal ring-cleavage.
As shown in Table 2, the parameters of the thermal ring-
cleavages indicate that the activation enthalpy 3DH ) for 5a
³
or 5b!13 is much smaller than those for 6a or 6b!16 or 8.
³
Interestingly, DH for 6a!16 is almost the same as that for
2.2. Thermal ring-opening of 5and 6
It is known that the benzocyclobutadiene dimers 5 undergo
thermal and silver-catalyzed isomerization to yield 13.5,17 In
a similar manner, treatment of anti-trimer 6a under re¯ux in
o-dichlorobenzene for 15 h produced 16 in 71% yield,
together with all-E-tribenzo[12]annulene 317) 32%)
3Scheme 5). The formation of 16 can be explained by the
initial formation of E,E,Z-tribenzo[12]annulene 318),
followed by the intramolecular [21212] cycloaddition.
The thermal reaction of syn-trimer 6b in re¯uxing o-dichloro-
benzene for 16 h produced the all-Z-tribenzo[12]annulene
38) in 90% yield, together with E,Z,Z-tribenzo[12]annulene
319) 33%).
As shown in Scheme 5, the thermal ring-opening of 6a and
6b is considered to proceed almost keeping the con®gura-
tion of the starting materials, presumably due to the rigidity
of their molecular framework. The X-ray analysis of 6a
shown in Fig. 1 reveals an almost planar cyclohexane
ring, and the maximum atomic deviation from the least-
Ê
Figure 1. Molecular structure of 6a. Selected bond lengths 3A) and angles
38): C1ZC2, 1.59033); C2ZC3, 1.53833); C3ZC4, 1.59333); C4ZC5,
1.52633); C5ZC6, 1.59733); C6ZC1, 1.51733); C1ZC2ZC3, 118.832);
C2ZC3ZC4, 120.332); C3ZC4ZC5, 120.532); C4ZC5ZC6, 118.832);
C5ZC6ZC1, 120.531).

3570
Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
Table 2. Parameters of the thermal reaction of 5a,a 5b,b 6a,c 6b,d 20,e and
21f
³
³
Compound
DH 3kcal mol-1)
DS 3cal mol-1´K)
5a
5b
6a
6b
20
21
27.54^0.06
28.31^0.21
42.0^1.2
32.7^0.9
41.3^0.9
31.0^0.7
2.8^0.2
3.3^0.6
13.3^2.5
1.8^2.0
0.75
6.5^0.8
a
Parameters from 5a to 13.
Parameters from 5b to 13.
Parameters from 6a to 16.
Parameters from 6b to 8.
Parameters from 20 to 22.
Parameters from 21 to 23.
b
c
d
e
f
∆
5
Scheme 7. Dehydrogenation of 6.
20
to dehydrogenation with Pd±C in re¯uxing p-cymene. It is
worth noting that the 1H NMR spectrum of 25 shows fairly
high ®eld shifts of AA0BB0 signals [d 6.45±6.48 3AA0, 2H),
6.79±6.82 3BB0, 2H)]. As shown in Scheme 7, the molecular
structure of 25 estimated by MOPAC AM1 calculations
adopts a concave p-system, and one benzene ring locates
in the shielding region of the other two benzene rings.
22
21
23
Scheme 6. Thermal reactions of 5, 20, and 21.
The formation of 24 can be explained by the skeletal
rearrangement from the cationic intermediate 26, which
can be generated by a direct hydride abstraction or a step-
wise oxidation via a radical intermediate.20 As shown in
Scheme 8, oxidation of 6a with DDQ affords the cation
26, which undergoes 1,2-alkyl-shifts on two occasions to
³
20!22,9c whereas DH for 6b!8 is similar to that for
³
21!2319 3Scheme 6). Since DS in the latter is comparable,
the transition state in the two reactions is similar. In the
³
former, however, DS for 6a!16 is much larger than that
for 20!22, and hence the transition states between these
two cases are different. The rate-controlling step for 6a!16
³
may be the isomerization 18a!18b, re¯ecting a large DS
value. The thermal reaction of 5a may proceed with inver-
sion of stereochemistry via the o-xylylene derivative
DDQ
6a
³
3Scheme 6).17b Surprisingly, DH for 5a!13 with inversion
is smaller than that for 5b!13 without inversion.17b±e
26
2.3. Dehydrogenation of 6
- H+
Tris3benzocyclobutadieno)benzene 37) is of considerable
interest because of its unique p-electron system.8,21 If the
central cyclohexane ring in 6 is dehydrogenated to the
benzene ring, it may be a simple method for preparing 7.
However, dehydrogenation of 6a with DDQ 33 equiv.) in
re¯uxing anisole for 3 h resulted in the formation of diben-
zo[a,e]indeno[1,3-c,d]azulene 324) in 13% yield 3Scheme
7). The formation of 24 can be detected easily, because 24
shows an intense red color in solution, re¯ecting its azulene
chromophore.22 On the other hand, treatment of 6b with
DDQ 33 equiv.) in re¯uxing toluene for 3 h produced the
didehydrogenated derivative 25 in 63% yield. The
compound 25 is stable to prolonged heating with DDQ or
27
DDQ
- H+
24
Scheme 8. Plausible mechanism for the formation of 24.

Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
3571
I
I
a
b
+
2
OH
OH
OH
HOH2C
CH2OH
29
11
12
28
OH
OH
e
c
d
CHO
OHC
30
31
O
O
OH
OH
h
f
g
8
O
O
34
32
33
S
Scheme 9. Synthesis of 8. Conditions: 3a) Pd3PPh3)4, CuI, Et3N; 3b) H2, Lindlar catalyst, THF; 3c) PCC, CH2Cl2; 3d) VCl33THF)3, Zn, THF; 3e) 3COCl)2,
DMSO, Et3N, CH2Cl2; 3f) NaBH4, EtOH, CH2Cl2, 08C; 3g) TCDI 3thiocarbonyldiimidazole), toluene, re¯ux; 3h) DMPD 31,3-dimethyl-2-phenyl-1,3,2-
diazaphospholidine), benzene, re¯ux.
form the isomeric cation 27. Deprotonation of 27, followed
by dehydrogenation with DDQ and ring-opening, produces
the indenoazulene derivative 24.
2.5. Synthesis, structure, and properties of metal
complexes derived from 8
On the basis of the calculated molecular structure of 8 by
MOPAC AM1, p-electrons of the benzene rings and the
ethylene linkages are orthogonal and cannot conjugate
with each other. Thus, 38) shows no delocalization in the
2.4. Stepwise synthesis of all-Z-tribenzo[12]annulene *8)
Since all-Z-tribenzo[12]annulene 38) bears a rigid, crown-
like structure with C3v symmetry, 8 can be expected to
behave like a p-prismand.10 In addition, 8 contains three
ethylene groups arranged with C3 symmetry, and hence
these ethylene groups can take part in the metal complexa-
tion as a p-host molecule. The synthetic route for 8 starting
from 1 is quite short, but the total yield of 8 is not suf®-
ciently high to allow investigation of the properties of 8.
Therefore, we developed a new route to synthesize 8
3Scheme 9). The palladium-catalyzed cross-coupling reac-
tion of 2-hydroxymethylphenylacetylene 312) 32 equiv.)
with 1,2-diiodobenzene 11 31 equiv.) in re¯uxing triethyl-
amine in the presence of CuI for 15 min produced 28 in 94%
yield. Partial reduction of 28 using the Lindlar catalyst
[Pd±Pb3OAc)2 on CaCO3] in THF at room temperature
370±77%), followed by oxidation of 29 with PCC 382%),
afforded the corresponding diene-dialdehyde 30. Pinacol-
coupling of the dialdehyde 30 with a low-valent vanadium
complex23 in THF at room temperature for 5 h yielded the
threo-diol 31 382%). Swern oxidation of the diol 31
produced the annulenedione 32 in 86% yield. Reduction
of 32 with NaBH4 in ethanol±CH2Cl2 afforded the
erythro-isomer 33 380%) with a small amount of the
threo-isomer 31. The reaction of 33 with TCDI 3thiocarbo-
nyldiimidazole) in re¯uxing toluene led to the thionocarbo-
nate 34 378%) which was converted into 8 384%) by the
reaction with DMPD 31,3-dimethyl-2-phenyl-1,3,2-diaza-
phospholidine) [modi®ed Corey±Winter procedure].24
Z,Z,Z-Tribenzo[12]annulene 38) was synthesized in 22%
overall yield based on 12.
Scheme 10. Metal complexes of 8.

3572
Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
macrocyclic ring, but a face-to-face geometry of the three
benzene rings and three ethylene units in 8 makes it possible
for 8 to behave like p-prismand. In order to evaluate the
possibility of p-electron delocalization among its three
benzene rings, the 3h6-arene)chromium tricarbonyl
complex 35 was prepared by treatment of 8 with Cr3CO)6
in diglyme±THF 34:1) under re¯ux for 10 h. However, the
electronic spectra of 35 and 8 showed no through-space and
through-bond interaction of the benzene rings, in contrast to
the case of deltaphane.10b
as a broad singlet at room temperature, also due to an
equilibrium in solution.
Single crystals of 36 were obtained by recrystallization from
hexane±dichloromethane, and its crystal structure was
determined by X-ray analysis. As shown in Fig. 2a, the
silver atom in 36 locates in the center of the cavity of the
[12]annulene. The AgZC3ole®n) distances of the complex
Ê
36 vary only in the range from 2.53039) to 2.68739) A
Ê
3average 2.61 A), indicating almost equal coordination
with the three ethylene units. The average AgZC distance
Ê
Ê
Secondly, we attempted to synthesize the complexes 9 and
10 3Scheme 10) with AgOTf, since B3LYP density func-
tional calculations for 9 and 10 suggest that 9 is less stable
than 10, but the energy difference in the heat of formation
between 9 and 10 is small 3EAgˆ2.4 kcal mol21).11d The
reaction of 8 with AgOTf 31.5 equiv.) in THF afforded the
32.61 A) is longer than those 32.36±2.53 A) of most of the
reported silver complexes with alkenes,25,26 and is com-
Ê
parable to that 32.65 A) of the AgNO3 1:1 adduct with
cyclooctatetraene.27 The annulene ring shows no large
distortion, and the distances [average CvC3alkene)
Ê
1.33 A estimated by B3LYP calculation] and angles of the
1
corresponding silver complex 36 in 82% yield. The H
alkene parts are similar values to those of 8. Interestingly,
the plane Ag1±C1±C2 is not perpendicular to the C1±C2±
C3±C12 plane but rather forms an angle of 768 with it. Thus,
the silver ion is distorted by an average 148 in the direction
of the cis hydrogens; i.e., Ag1 locates slightly outside the
coordination site of the three alkene ligands. A similar
observation was made for the AgNO3 3:1 complex with
Z,Z,Z-1,4,7-cyclononatriene.27 As shown in Fig. 2b, the
silver ion is bonded to two oxygen atoms of the different
NMR spectrum of 36 clearly indicates formation of the
silver complex in solution. Since the ole®nic protons at d
6.76 in 8 shift to down®eld d 7.48, the structure of the
complex can be assigned to the ole®nic complex 10.
However, the aromatic protons at d 6.95 and 7.07 in 8
also shift to down®eld d 7.09 in 36, and the benzenoid
complex 9 might coexist at equilibrium in solution. The
1H NMR signal of the ole®nic protons in 36 was observed
Ê
Figure 2. ORTEP diagram of 36: 3a) side view; 3b) packing diagram. Selected bond lengths 3A) and angles 38): Ag1ZO1, 2.40436); Ag1ZO2, 2.50639);
Ag1ZC1, 2.53039); Ag1ZC2, 2.53238); Ag1ZC5, 2.57338); Ag1ZC6, 2.61139); Ag1ZC9, 2.68739); Ag1ZC10, 2.62439); C1ZC2, 1.3131); C2ZC3,
1.490310); C3ZC4, 1.3931); C4ZC5, 1.4731); C1ZC12, 1.5131); C1ZC2ZC3, 124.537); C2ZC3ZC4, 122.437); C2ZC1ZC12, 126.637).

Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
3573
counter anions at AgZO distances of 2.40436) and 2.50639)
Ê
A to form a one-dimensional polymer. There is no inter-
action observed between the silver ion and the benzene
rings.
brs), 3.76 34H, s); 13C-NMR 322.5 MHz, CDCl3) d 147.6,
127.5, 122.8, 49.8. Anal. Found: C, 93.74; H, 5.91%. Calcd
for C16H12: C, 94.08; H, 5.92%.
3.2.2. syn-Dimer 5b. Colorless crystals 3hexane), mp
122.5±123.58C 3decomp.); MS3EI) m/z 204 3M1); IR
3KBr) 2990, 1457, 1172, 740, 462 cm21; UV 3cyclohexane)
In summary, we have shown two routes for the synthesis of
8, a cage molecule with a concave p-system. Since 8 can
behave as a biconcave host like 9 and 10, an interesting
host±guest chemistry might be expected using 8 and its
derivatives.
l
max 3log 1) 257sh 33.15), 263 33.58), 269 33.54), 276 33.51)
nm; 1H-NMR 390 MHz, CDCl3) d 6.98±6.72 38H, m), 4.09
34H, s); 13C-NMR 322.5 MHz, CDCl3) d 145.7, 126.8,
122.6, 41.4. Anal. Found: C, 93.94; H, 5.93%. Calcd for
C16H12: C, 94.08; H, 5.92%.
3. Experimental
3.1. General
3.2.3. anti-Trimer 6a. Colorless prisms 3CH2Cl2±hexane),
mp 161.5±163.58C 3decomp.); MS3EI) m/z 306 3M1); IR
3KBr) 3056, 2898, 1600, 1457, 1181, 1154, 996, 935, 745,
553 cm21; UV 3cyclohexane) lmax 3log 1) 213sh 33.75), 262
Melting points were determined on a hot-stage apparatus
and are uncorrected. IR spectra were taken with Hitachi
EPI-G3 or Perkin±Elmer 1600 spectrometers and only
signi®cant maxima are described. Electronic spectra were
measured with Shimadzu U-3400 or UV-3101PC spectro-
meters. Mass spectra were recorded with JEOL JMS01SG-2,
JMS-SX102 or JMS-AX500 spectrometers using a direct-
1
32.95), 268 33.11), 274 33.08) nm; H-NMR 3500 MHz,
CDCl3) d 7.30±7.26 32H, m), 7.23±7.20 32H, m), 7.09±
7.00 38H, m), 4.16±4.11 32H, m), 4.09 32H, s), 4.04±3.99
32H, m); 13C-NMR 3125 MHz, CDCl3) d 148.4, 148.3,
146.8, 127.6, 126.8, 126.7, 124.0, 121.6, 121.1, 42.9, 42.5,
40.5. Anal. Found: C, 94.13; H, 5.92%. Calcd for C24H18: C,
94.08; H, 5.92%.
1
inlet system. H-NMR spectra were recorded on a Varian
XL-100A 3100 MHz) or JEOL JNM-LA500 3500 MHz)
spectrometer with TMSas the reference. 13C-NMR spectra
were recorded on a JEOL FX90Q 322.5 MHz) or JNM-
3.2.4. syn-Trimer 6b. Colorless needles 3CH2Cl2±hexane),
mp 191.5±192.58C 3decomp.); MS3EI) m/z 306 3M1); IR
3KBr) 3057, 2920, 1455, 1360, 1203, 1106, 998, 747, 655,
582, 495 cm21; UV 3cyclohexane) lmax 3log 1) 218sh
LA500 3125 MHz) spectrometers with TMSor CDCl
377.02 ppm) as the reference.
3
1
34.23), 262 33.53), 268 33.63), 275 33.54) nm; H-NMR
3500 MHz, CDCl3) d 7.02±6.99 36H, m), 6.98±6.95 36H,
m), 4.19 36H, s); 13C-NMR 3125 MHz, CDCl3) d 147.2,
126.4, 123.7, 40.6. Anal. Found: C, 93.96; H, 5.90%.
Calcd for C24H18: C, 94.08; H, 5.92%.
The reaction solvents were distilled after an appropriate
drying procedure. Progress of reactions was followed by
TLC on Merck pre-coated silica gel 3Kieselgel 60F254).
Alumina 3Merck, activity II±III) or silica gel 3Daiso gel
1001W or Merck Art. 1097) was used for column chromato-
graphy.
3.3. X-ray crystallography of 6a
X-ray diffraction data were collected on a Rigaku AFC5R
diffractometer with MoKa radiation. The structures were
solved by direct method and re®ned using full-matrix
least-squares analysis. Anisotropic thermal parameters
were used for non-hydrogen atoms. Crystal data: C24H18,
Mwˆ306.41, monoclinic, space group P21/n 3No. 14),
3.2. General procedure for cyclooligomerization of 1
*Table 1)
A suspension of NiBr2L2 3LˆPPh3 or PBun , 0.8 mmol),
3
activated zinc powder 31.05 g, 16 mmol), and an additive
[1.6 mmol of PR3 3RˆPh or Bun) or 8.0 mmol of iodide:
Et4NI or NaI] in dry solvent 3benzene, THF or DMF; 10 ml)
was degassed and the ¯ask was ®lled with gaseous
argon. Then the suspension was irradiated with ultrasonic
waves for 5 min and was stirred for 45 min under argon
atmosphere. To the suspension was added dropwise with a
syringe over 2 h a degassed solution of compound 1 31.05 g,
4.0 mmol) in each solvent 310 ml) and the reaction mixture
was stirred for 15 h at room temperature. The mixture was
®ltered off and washed with benzene. The ®ltrate and wash-
ings were combined and concentrated, and the residue was
passed through a short plug of alumina eluted by a mixture
of benzene and hexane. After concentration of the elution,
the residue was chromatographed on silica gel. The frac-
tions eluted with hexane±benzene afforded the products.
Ê
Ê
Ê
aˆ9.19931) A, bˆ14.77032) A, cˆ12.34831) A, bˆ
Ê 3
23
106.88739)8, Vˆ1605.433) A , Zˆ4, Dcˆ1.27 g cm
,
Rˆ0.043, Rwˆ0.053, GOFˆ1.40 for 2300 re¯ections with
I.3.0s3I).
3.4. Thermal isomerization of the trimers *6a, 6b)
A
solution of anti-trimer 330.8 mg, 0.10 mmol) in
o-dichlorobenzene 350 ml) was heated under re¯ux for
15 h in an argon atmosphere. After cooling to room
temperature, the reaction mixture was concentrated to
dryness under reduced pressure and the residue was sepa-
rated by chromatography on silica gel with hexane as eluent.
The products 316: 21.9 mg, 71%; 17: 0.65 mg, 2%) isolated
here showed spectroscopic data identical with those in the
literature.21
3.2.1. anti-Dimer 5a. Colorless crystals 3hexane), mp
132.5±133.58C 3decomp.); MS3EI) m/z 204 3M1); IR
3KBr) 2968, 1453, 1148, 997, 754, 746 cm21; UV 3cyclo-
hexane) lmax 3log 1) 257sh 33.28), 265sh 33.53), 271 33.82),
In a similar manner, 8 382.5 mg, 90%) and 19 32.9 mg, 3%)
were obtained from thermal reaction of 6b 392 mg,
0.30 mmol) in diclorobenzene 350 ml) for 16 h.
1
278 33.93) nm; H-NMR 3100 MHz, CDCl3) d 7.20 38H,

3574
Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
3.4.1. All-Z-tribenzo[12]annulene *8). Colorless plates
3EtOH), mp 185.5±186.08C; MS3EI) m/z 306 3M1); IR
3KBr) 2990, 1690, 1635, 1467, 1449, 1392, 1087, 948,
863, 802, 773, 746, 704, 662, 570, 490 cm21; UV 3cyclo-
hexane) lmax 3log 1) 219sh 34.50), 267sh 33.23) nm;
1H-NMR 3500 MHz, CDCl3) d 7.09±7.05 36H, m), 6.96±
6.93 36H, m), 6.76 36H, s); 13C-NMR 3125 MHz, CDCl3) d
136.2, 132.2, 129.9, 125.8. Anal. Found: C, 94.03; H,
5.96%. Calcd for C24H18: C, 94.08; H, 5.92%.
127.8, 127.6, 125.2, 121.2, 92.6, 90.9, 63.8. Anal. Found:
C, 85.03; H, 5.27%. Calcd for C24H18O2: C, 85.18; H,
5.36%.
3.7. 1,2-Phenylenebis*2-Z-ethenylbenzyl alcohol) *29)
In a 300 ml round-bottomed ¯ask, 500 mg of Lindlar
catalyst 3Pd±Pb3OAc)2 on CaCO3) was added to a solution
of the diyne 28 31.69 g, 5.00 mmol) in THF 3150 ml) and the
mixture was vigorously stirred for 14 h under H2
atmosphere. The reaction mixture was ®ltered and evapo-
rated to dryness under reduced pressure. The residual solid
was puri®ed by recrystallization from acetone±isopropyl
ether to afford 1.31 g 377%) of the diene-diol 29 as colorless
needles, mp 111.4±113.58C; IR 3KBr) 3211, 2869, 1458,
1046, 1020, 777, 749 cm21; UV 3THF) lmax 3log 1), 261
34.54), 255 34.60), 249 34.59) nm; MS3EI) 342 3M 1);
1H-NMR 3500 MHz, CDCl3) d 7.37 32H, d, Jˆ7.5), 7.19
32H, t, Jˆ7.5), 7.05 32H, t, Jˆ7.5), 6.96±6.93 32H, m),
6.91±6.89 34H, m), 6.81 34H, s), 4.65 34H, s), 1.75 32H,
brs); 13C-NMR 3125 MHz, CDCl3) d 138.4, 135.9, 135.7,
130.2, 129.7, 129.4, 128.9, 127.9, 127.50, 127.46, 126.8,
63.4. Anal. Found: C, 84.22; H, 6.55%. Calcd for
C24H22O2: C, 84.18; H, 6.48%.
3.5. Dehydrogenation of the trimers *6a, 6b)
A solution of the trimer 6a 3152 mg, 0.50 mmol) and DDQ
3380 mg, 1.6 mmol) in anisole 330 ml) was heated under
re¯ux for 3 h in an argon atmosphere. After cooling to
room temperature, the reaction mixture was concentrated
under reduced pressure and the residue was separated by
chromatography on silica gel with CH2Cl2±hexane as
eluent. The red elution was collected and evaporated to
afford 24 320 mg, 13%), the spectral data of which were
identical with those of the literature.22
In a similar manner, syn-trimer 6b 38.0 mg, 26 mmol) was
dehydrogenated with DDQ 320 mg, 78 mmol) in re¯uxing
toluene 38 ml) for 3 h to afford 25 35.0 mg, 63%); colorless
plates 3hexane), mp 178.5±179.58C; MS3EI) m/z 304 3M1);
IR 3KBr) 3052, 2911, 1461, 1435, 1362, 1196, 1157, 990,
910, 757, 743, 722, 662, 582, 471 cm21; UV 3cyclohexane)
3.8. 1,2-Phenylenebis*2-Z-ethenylbenzaldehyde) *30)
To a solution of the diene-diol 29 3524 mg, 1.5 mmol) in
CH2Cl2 380 ml) was added pyridinium chlorochromate
31.29 g, 6 mmol) and the resulting suspension was stirred
at room temperature for 2 h. The reaction mixture was
diluted with ether and ®ltered through a Celite pad, which
was washed with ether. The combined ®ltrate and
washings were concentrated under reduced pressure and
the residual oil was puri®ed by column chromatography
on silica gel eluted by benzene±ethyl acetate. After
evaporation of the solvent, 418 mg 382%) of the dialdehyde
30 was obtained as colorless solid. Pure sample was
obtained by recrystallization from isopropyl ether, mp
98.8±101.18C; IR 3KBr) 3060, 2841, 2720, 1693, 1594,
782, 764 cm21; UV 3THF) lmax 3log 1), 260 34.59), 254
34.67), 249 34.68) nm; MS3EI) 338 3M 1); 1H-NMR
3500 MHz, CDCl3) d 10.21 32H, s), 7.81 32H, dd, Jˆ7.0,
2.0), 7.37±7.32 34H, m), 7.10 32H, d, Jˆ12.0), 6.96 32H, dd,
Jˆ7.0, 2.0), 6.92 32H, d, Jˆ12.0), 6.91±6.87 34H, m);
13C-NMR 3125 MHz, CDCl3) d 192.0, 140.1, 135.4,
133.5, 131.6, 130.8, 130.2, 129.9, 128.4, 127.6, 127.1.
Anal. Found: C, 85.04; H, 5.33%; Calcd for C24H18O2: C,
85.18; H, 5.36%.
l
max 3log 1) 226 34.02), 236 33.93), 246 33.82), 267sh 33.96),
273 34.08), 283 34.20), 293sh 34.18), 296 34.22), 306sh
1
34.25), 311 34.56), 322sh 34.34), 328 34.65) nm; H-NMR
3500 MHz, CDCl3) d 7.39±7.36 32H, m), 7.21±7.17 34H,
m), 7.04±7.01 32H, m), 6.82±6.79 32H, m), 6.48±6.45 32H,
m), 4.34±4.33 32H, m), 4.26±4.23 32H, m); 13C-NMR
3125 MHz, CDCl3) d 149.8, 144.2, 143.8, 127.95, 127.93,
127.8, 126.8, 122.69, 122.68, 119.9, 48.33, 48.26. Anal.
Found: C, 94.41; H, 5.34%. Calcd for C24H16: C, 94.70;
H, 5.30%.
3.6. 1,2-Phenylenebis*2-ethynylbenzyl alcohol) *28)
To a solution of ethynylbenzyl alcohol 38.22 g, 62 mmol)
and o-diiodobenzene 39.90 g, 30 mmol) in triethylamine
3150 ml) were added copper3I) iodide 3116 mg, 0.6 mmol)
and Pd3PPh3)4 3356 mg, 0.3 mmol). The resultant mixture
was heated to re¯ux and stirred for 15 min under Ar
atmosphere. After cooling to room temperature, the reaction
mixture was diluted with 2 M HCl 3250 ml) and saturated
aqueous NH4Cl 3250 ml) and extracted with dichloro-
methane. The combined organic extracts were washed
with saturated aqueous NH4Cl and dried over MgSO4.
After evaporation of the solvent, the residual solid was puri-
®ed with chromatography on silica gel with a mixture of
benzene and ethyl acetate as eluent. The solid product
obtained by concentration of the elution was recrystallized
from acetone±benzene to afford 9.57 g 394%) of colorless
needles, mp 124.0±125.68C; IR 3KBr) 3337, 3246, 1490,
1032, 756 cm21; UV 3THF) lmax 3log 1), 314 34.49), 261
34.77), 255 34.78), 249 34.79), 243 34.77) nm; MS3EI) 338
3.9. threo-Pinacol 31
In a three-necked 100 ml ¯ask attached with a dropping
funnel, a three-way stop cock connected to an N2 supply
and a stopper, was placed VCl33THF)3 31.21 g, 3.2 mmol)
under nitrogen atmosphere, which was dissolved in 20 ml of
THF. Zn powder 3212 mg, 3.2 mmol) was added and the
resultant mixture was stirred for 30 min. A solution of the
dialdehyde 30 3678 mg, 2.0 mmol) in 20 ml of THF was
added dropwise for 2.5 h to the stirred mixture. After addi-
tional stirring for 2.5 h, the reaction mixture was diluted
with ethyl acetate 340 ml) and saturated aqueous NaHCO3
350 ml) was added. The resultant mixture was stirred for 1 h
3M1); H-NMR 3500 MHz, CDCl3) d 7.60±7.57 34H, m),
7.45 32H, d, Jˆ7.5), 7.38±7.35 32H, m), 7.29 32H, t, Jˆ7.5),
4.84 34H, d, Jˆ6.0), 2.64 31H, t, Jˆ6.0); 13C-NMR
3125 MHz, CDCl3) d 142.8, 132.4, 132.2, 129.1, 128.4,
1

Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
3575
and ®ltered by suction. The organic phase of the ®ltrate was
separated and the aqueous phase was extracted with ethyl
acetate 32£50 ml). The combined organic phase was washed
with saturated aqueous NH4Cl and dried over MgSO4. After
removal of the solvent, the residual solid mass was sepa-
rated by chromatography on silica gel with benzene±ethyl
acetate as eluent. The solid product obtained by concentra-
tion of the corresponding fraction was puri®ed by recrystal-
lization from dichloromethane and isopropyl ether to afford
556 mg of colorless prisms, mp 216.3±217.78C; IR 3KBr)
3354, 3056, 2915, 1400, 1026, 799, 766 cm21; UV 3THF)
Jˆ12.5), 5.73 31H, d, Jˆ12.5), 5.60 31H, d, Jˆ12.5), 5.26
31H, dd, Jˆ3.5, 2.0), 5.21 31H, dd, Jˆ4.0, 2.0), 4.51 31H, d,
Jˆ4.0), 4.47 31H, d, Jˆ3.5); 13C-NMR 3125 MHz, CDCl3)
d 139.6, 138.2, 135.6, 135.2, 134.1, 133.4, 132.1, 131.8,
130.7, 129.7, 129.1, 128.6, 127.9, 127.8, 127.62, 127.59,
127.5, 127.2, 127.01, 126.95, 126.7, 125.1, 82.63, 73.41.
3.11. Thionocarbonate 34
A solution of erythro-diol 33 3204 mg, 0.6 mmol) and thio-
carbonyl-diimidazole 3TCDI, 125 mg, 0.7 mmol) in toluene
315 ml) was heated under re¯ux for 18 h in an argon
atmosphere. After cooling to room temperature, the reaction
mixture was concentrated to dryness and the residual solid
was puri®ed by column chromatography on silica gel with
benzene±hexane as eluent. The solid product obtained by
concentration of the corresponding fraction was recrystal-
lized from CH2Cl2±isopropyl ether to afford 179 mg 378%)
of colorless plates, mp 231.1±232.38C; IR 3KBr) 3004,
l
max 3log 1), 260 34.46), 255 34.51), 249 34.54) nm; MS3EI)
340 3M1); H-NMR 3500 MHz, CDCl3) d 7.85 32H, d,
Jˆ7.5), 7.24±7.21 34H, m), 7.05±7.03 32H, m), 6.93 32H,
t, Jˆ7.5), 6.63 32H, d, Jˆ7.5), 5.89 32H, d, Jˆ12.0), 5.70
32H, d, Jˆ12.0), 4.91 32H, s), 3.37 32H, brs); 13C-NMR
3125 MHz, CDCl3) d 137.4, 137.2, 133.6, 132.0, 129.2,
127.6, 127.45, 127.37, 127.27, 126.8, 124.5, 73.4. Anal.
Found: C, 84.50; H, 5.79%; Calcd for C24H20O2: C, 84.68;
H, 5.92%.
1
1470, 1366, 1325, 1308, 1273, 1160, 970, 935, 743 cm21
;
MS3EI) 382 3M 1); 1H-NMR 3500 MHz, CDCl3) d
7.28±7.24 34H, m), 7.16±7.13 32H, m), 7.02 32H, d,
Jˆ7.5), 6.99 32H, td, Jˆ7.5, 1.5), 6.94 32H, td, Jˆ7.5,
1.5), 6.83 32H, d, Jˆ12.2), 6.77 32H, d, Jˆ12.2), 6.43
32H, s); 13C-NMR 3125 MHz, CDCl3) d 191.1, 135.4,
134.9, 134.2, 130.7, 130.5, 129.9, 129.5, 128.4, 127.0,
126.6, 126.3, 83.4. Anal. Found: C, 78.29; H, 5.02%;
Calcd for C25H18O2S: C, 78.51; H, 4.74%.
3.10. erythro-Pinacol 33
A solution of oxalyl chloride 30.8 ml, 9.2 mmol) in 30 ml of
CH2Cl2 was cooled to 2788C 3bath temp.) and a solution of
dimethylsulfoxide 31.0 ml, 14.1 mmol) in 10 ml of CH2Cl2
was added dropwise. After stirring for 15 min, a solution of
31 3683 mg, 2.0 mmol) in THF 330 ml) was added dropwise
and the resulting mixture was warmed to ca. 2608C and
stirred for 15 min. A solution of Et3N 32.0 ml, 14.3 mmol)
in THF 310 ml) was added dropwise, and the resultant
mixture was stirred with gradual warming to 2308C for
1 h. After additional stirring for 1 h with removal of the
cold bath, the reaction mixture was poured into saturated
aqueous NH4Cl and extracted with ether 33£50 ml). The
combined extract was washed with water and saturated
aqueous NH4Cl successively and dried over MgSO4. After
evaporation of the solvent, the residual oil was puri®ed by
chromatography on silica gel with benzene as eluent.
Recrystallization of the solid mass obtained by evaporation
of the corresponding elution afforded the dione 32 3578 mg,
86%) as yellow needles, mp 198.1±199.88C; MS3EI) 336
3M1); Anal. Found: C, 85.49; H, 4.60%; Calcd for
C24H16O2: C, 85.69; H, 4.79%.
3.12. All-Z-tribenzo[12]annulene *8)
A solution of thionocarbonate 337.8 mg, 0.1 mmol) and 1,3-
dimethyl-2-phenyl-1,3,2-diazaphospholidine 3DMPD, 42.5
mg, 0.2 mmol) in benzene 34 ml) was heated under re¯ux
for 15 h in an argon atmosphere. After cooling to room
temperature, the reaction mixture was concentrated and
the residual oil was separated by chromatography on silica
gel with benzene±hexane as eluent. The product 38,
25.3 mg, 84%) was obtained after concentration of the
corresponding fraction.
3.13. Tribenzo[12]annulene chromium tricarbonyl
complex *35)
A solution of 8 330 mg, 0.10 mmol) and Cr3CO)6 366 mg,
0.30 mmol) in a mixture of diglyme 320 ml) and THF 35 ml)
was heated under re¯ux for 10 h in an argon atmosphere.
After cooling to room temperature, the reaction mixture was
concentrated and the residual solid was separated by chro-
matography on silica gel with CH2Cl2±hexane as eluent.
The crude product obtained by concentration of the corre-
sponding fraction was recrystallized to afford yellow
needles 335, 16 mg, 36%), mp ca. 1608C 3decomp.); IR
3KBr) 1960, 1887 cm21 3CvO); UV 3cyclohexane) lmax
3log 1), 326 33.88), 254sh 33.87) nm; MS3EI) 442 3M 1);
1H-NMR 390 MHz, CDCl3) d 7.26±7.07 38H, m), 6.87 32H,
d, Jˆ12), 6.66 32H, s), 6.62 32H, d, Jˆ12), 5.26±5.14 32H,
m), 5.02±4.92 32H, m).
The dione 32 3336 mg, 1.0 mmol) was dissolved in a
mixture of ethanol and CH2Cl2 310 ml each) and NaBH4
338 mg, 1.0 mmol) was added. After stirring for 1.5 h at
room temperature, the reaction mixture was poured into
saturated aqueous NH4Cl 3100 ml) and extracted with
ether 33£30 ml). After drying over MgSO4, the combined
extract was concentrated to dryness under reduced pressure
and the residual solid was puri®ed by chromatography on
silica gel to afford erythro-diol 33 3271 mg, 80%) together
with threo-diol 31 315 mg, 5%) after evaporation of the
corresponding fraction followed by recrystallization from
ether±hexane. The erythro-diol 33 was obtained as colorless
plates, mp 203.4±204.48C; IR 3KBr) 3421, 3060, 2890,
1486, 1070, 1021, 798, 767 cm21; MS3EI) 340 3M 1);
1H-NMR 3500 MHz, CDCl3) d 7.90 31H, d, Jˆ7.5), 7.32
31H, d, Jˆ7.5), 7.24±7.17 33H, m), 7.11±7.06 33H, m), 6.92
31H, t, Jˆ7.5), 6.84 31H, t, Jˆ7.5), 6.67 31H, d, Jˆ12.5),
6.59 31H, d, Jˆ7.5), 6.57 31H, d, Jˆ7.5), 6.01 31H, d,
3.14. Tribenzo[12]annulene silver tri¯ate complex *36)
Tribenzo[12]annulene 8 310 mg, 33 mmol) was treated with
AgOTf 312 mg, 49 mmol) in THF 35 ml) under argon

3576
Y. Kuwatani et al. / Tetrahedron 57 12001) 3567±3576
11. 3a) Iyoda, M.; Kuwatani, Y.; Yamauchi, T.; Oda, M. J. Chem.
Soc., Chem. Commun. 1988, 65. 3b) Kuwatani, Y.; Kusaka, A.;
Iyoda, M.; Yamamoto, G. Tetrahedron Lett. 1999, 40, 2961.
3c) Kuwatani, Y.; Yoshida, T.; Kusaka, A.; Iyoda, M.
Tetrahedron Lett. 2000, 41, 359. 3d) Yoshida, T., Kuwatani,
Y., Hara, K., Yoshida, M., Matsuyama, H., Iyoda, M., Nagase,
S. Tetrahedron Lett., in press
atmosphere. After stirring for 30 min, the reaction mixture
was concentrated to dryness and the residual solid was
recrystallized from CH2Cl2±hexane to afford 15 mg 382%)
of colorless prisms, mp 180±1818C 3decomp.); H-NMR
3500 MHz, CDCl3, 2308C) d 7.54 36H, s), 7.13 36H, s).
1
12. For a review, see: Grotjahn, D. B. In Comprehensive Organo-
metallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson,
G., Eds.; Pergamon: Oxford, 1995; Vol. 12, p. 741.
13. 3a) Binger, P.; Schroth, G.; McMeeking, J. Angew. Chem., Int.
Ed. Engl. 1974, 13, 465. 3b) Binger, P.; Doyle, M. J.;
McMeeking, J.; KruÈger, C.; Tsay, Y.-H. J. Organomet.
Chem. 1977, 135, 405. 3c) Hashimi, A. S.; Naumann, F.;
Probst, R.; Bats, J. W. Angew. Chem., Int. Ed. Engl. 1997,
36, 104.
Acknowledgements
Financial support for this study was provided by Grant-in-
Aids for Scienti®c Research on Priority Areas from the
Ministry of Education, Science and Culture, Japan
306224223 and 12042267). We thank Mr. Tetsuhiro
Yamauchi and Mr. Toshihiro Sauchi for preliminary
reactions of 1 with nickel complexes.
14. For reviews, see: 3a) Heck, R. F. In Palladium Reagents in
Organic Synthesis; Academic Press: New York, 1985; p. 322.
3b) Tsuji, J. In Palladium Reagents and Catalysts; Wiley &
Sons: Chichester, 1995; p. 422.
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