Photoinduced electron transfer across linearly fused oligo-norbornyl structures

Article abstract of DOI:10.1016/j.tet.2005.05.023

The rates of photoinduced electron transfer (ET) reactions across two oligo-norbornyl spacer groups (S), that is, structure 1 fused by two norbornadiene (NBD) units and structure 2 fused by three NBD units, are examined. Substituted naphthalene acted as an electron donor (D), whilst ethylene-1,2-dicarboxylate as an electron acceptor (A). ET rates were measured by fluorescence quenching experiments on these D-S-A dyads, and the results were correlated with reaction free energies according to the Marcus relationship. It was found that naphthalene with phenyl substituents showed relatively slower ET rates. The conformational flexibility of phenyl substituents may cause a hindrance on the electronic coupling between D and A. Another salient feature was the abnormally high quenching rates observed in nonpolar solvents such as cyclohexane, the results of which may be ascribed to a competing energy transfer process.

Full text of DOI:10.1016/j.tet.2005.05.023

Tetrahedron 61 (2005) 6967–6975
Photoinduced electron transfer across linearly fused
oligo-norbornyl structures
b
b
a
b
Tahsin J. Chow,a, Yan-Ting Pan, Yu-Shan Yeh, Yuh-Sheng Wen, Kew-Yu Chen
*
and Pi-Tai Choub
aInstitute of Chemistry, Academia Sinica, Taipei 115, Taiwan, ROC
bDepartment of Chemistry, National Taiwan University, Taipei 106, Taiwan, ROC
Received 28 March 2005; revised 9 May 2005; accepted 11 May 2005
Available online 4 June 2005
Abstract—The rates of photoinduced electron transfer (ET) reactions across two oligo-norbornyl spacer groups (S), that is, structure 1 fused
by two norbornadiene (NBD) units and structure 2 fused by three NBD units, are examined. Substituted naphthalene acted as an electron
donor (D), whilst ethylene-1,2-dicarboxylate as an electron acceptor (A). ET rates were measured by fluorescence quenching experiments on
these D–S–A dyads, and the results were correlated with reaction free energies according to the Marcus relationship. It was found that
naphthalene with phenyl substituents showed relatively slower ET rates. The conformational flexibility of phenyl substituents may cause a
hindrance on the electronic coupling between D and A. Another salient feature was the abnormally high quenching rates observed in
nonpolar solvents such as cyclohexane, the results of which may be ascribed to a competing energy transfer process.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
has the virtue of high symmetry as well as structural rigidity,
so that the D and A chromophores can be aligned linearly
across a s-skeleton. The distance between the centers of D
and A in compounds 1 and 2 is then adjustable by the
number of NB units. Their ET rates were found to correlate
well with both D–A distance and solvent polarities. For
example, varying the D–A distance from 1 (5.5!109 sK1
for 5a in diethyl ether) to 2 (5.4!107 sK1 for 7a) reduced
the ET rates by approximately two orders of magnitude. A b
value of 0.77 was estimated according to an exponential
decay relationship expressed in Eq. 6 (vide infra). The value
of electronic coupling element Hel can further be deduced,
which was found to be a function of D–A orientation and the
bonding nature of the spacer. Such information is valuable
for the future design of molecular devices utilizing these
spacer groups. In this report, a comprehensive work based
on the design and synthesis of analogues of compound 1 and
2 was performed to shed light on their associated ET
dynamics. Consequently, the mechanism of photoinduced
ET process is rigorously examined.
Electron transfer process occurs ubiquitously in many
physical and biological pathways, and the fundamental
and applications of which have received much attention.
Recent advances in this field have extended to the design of
molecular devices, in which donor (D) and acceptor (A)
pairs are ingeniously linked by covalent spacers (S) to form
D–S–A dyads. Electron transfers between D and A across S
in a controlled manner may thus, display useful function-
alities such as molecular rectifiers,1 switches,2 electro-
chemical sensors,3 photovoltaic cells,4 and nonlinear optical
materials,5 etc. Spacer groups that have been utilized are
versatile, including small molecules, for example, cyclo-
hexane,6 adamantane,7 bicyclo[2.2.2]octane,8 steroids,9 and
oligomers of various sizes, for example, polynorbornanes,10
and ladderanes,11 etc. Among numerous types of spacers,
rigid linear rod-shaped structures, however, are not
commonly seen.12,13 The highly symmetrical structures
reduce the complexity due to the constraint of geometrical
and conformational variations. In our previous studies on
photoinduced electron transfer (ET) reactions, the rates of
ET in two series of oligo-norbornyl (NB) derivatives (1 and
2) have been estimated.14 The geometry of these compounds
2. Results and discussion
2.1. Compounds preparation and characterization
Keywords: Electron transfer; Donor and acceptor; Poly-norbornyl; Marcus
relationship; Charge transfer.
Compounds 1 and 2 were prepared through a coupling
reaction of norbornadiene (NBD) catalyzes by
*
Corresponding author. Tel.: C886 2 27898552; fax: C886 2 27884179;
e-mail: tjchow@chem.sinica.edu.tw
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.05.023

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T. J. Chow et al. / Tetrahedron 61 (2005) 6967–6975
Co2(CO)6(PPh3).15 The naphthalene donor (D) groups of
4a–c and 6a–c were fused on by [4C2] cycloaddition of
respective o-quinodimethane derivatives.16 The two ortho-
bromo substituents of 4b and 6b were transformed to the
phenyl groups of 4d and 6d by Suzuki coupling reaction
using PhB(OH)2 and Pd(PPh3)4.17 The dicarboxylate
acceptor (A) groups of 5a–d and 7a–d were made by
[2C2] cycloaddition reactions with dimethyl acetylene-
dicarboxylate (DMAD) upon the catalysis of RuH2-
(CO)(PPh3)3.18 All compounds exhibited two-fold
symmetry on NMR spectral signals.
˚
distance was estimated to be 14.7 A. The p-faces of D and A
were aligned parallel to each other, yet not on the same plane.
2.2. Spectroscopic property
Figure 2 depicts the absorption and emission spectra of two
prototypical models 4c and 4d, in which 4c consists of two
major absorption bands on the long wavelength side of the
UV spectra. The one at 300–320 nm, corresponding to the
first (p, p*) transition of naphthalene moiety, is assigned to
the 1A/1Lb transition according to the Platt classifi-
cation,19 whereas the next higher level transition at 245–
290 nm is assigned to the 1A/1La transition (Fig. 2). Both
bands exhibit distinctive vibronic progressions as a result of
conformation rigidity. Excitation at 310 nm induced a
fluorescence at 320–380 nm. The high-energy edge of the
emission spectrum overlaps well with 0–0 band of
absorption. The nearly negligible amount of Stokes’ shift
reflects a high structural similarity between the ground and
excited states. Similar spectral features also appeared on 4a
and 4b.
X-ray diffraction analysis on a single crystal of 5c was
performed. An ORTEP drawing of the structure is shown in
Figure 1. It appears that the central skeleton of (NBD)2 is
zig-zag in shape. The special orientation between D and A
attached ontospacer 1 (i.e., 5a–c) is slightly different from that
attached onto spacer 2 (7a–c). For example, structure of 5c
consists of both D and A groups locked rigidly via the spacer
(S), forminga dihedralangle ofca. 1108. Theestimatedcenter-
˚
to-center distance was 10.9 A from the central bond of
naphthalene to the middle of the line connecting the two
carbonyl groups. In the homologous compound 7c, the D–A
Figure 2. Absorption and emission spectra of compounds 4c and 4d in
CH3CN.
In a sharp contrast, the UV spectra of diphenyl substituted
derivatives 4d–7d exhibit a quite different pattern. The
major absorption band of 4d is broad with a peak
wavelength at 258 nm (1Bb band), accompanied by a
Figure 1. Molecular structure of compound 5c in single crystal.

T. J. Chow et al. / Tetrahedron 61 (2005) 6967–6975
6969
shoulder at w280 nm (1La band). The S1 transition (1Lb
band) appears in low intensity at 310–335 nm (Fig. 2). It is
well understood that phenyl substituents at C-2 position
shift the 1Lb band bathochromically because of its
longitudinal polarization.20 The broad and featureless
shape is apparently caused by the rotational flexibility of
the phenyl groups. The fluorescence spectrum of 4d (lmax at
370 nm) exhibited a substantial red-shift (37 nm) and wider
full width at half maximum (fwhm w56 nm) comparing to
that of 4c (lmaxw343 nm, fwhm w26 nm). The broadening
of emission band in 4c indicates either a significant mixing
between phenyl p-orbitals and naphthalene chromophore
or, in part, the diphenyl conformational flexibility.
where Eox(D) and Ered(A) are the oxidation and reduction
potentials of D and A molecules, respectively, in aceto-
nitrile. E00(D) is the energy of 0–0 transition, rCD and rAK are
effective ionic radii, 3 is the dielectric constant of solvent,
and d is the center-to-center distance between D and A. An
C
K
22
˚
approximation was further, made on rZrD ZrA Z4.5 A.
With all of the values substituted into Eq. 1, the free
energies were calculated and listed in Table 2. Figure 3
shows a linear plot of DG versus 1/3. Obviously, the ET
processes are calculated to be exothermic in most solvents,
except in a few nonpolar media such as n-hexane.
The rates of ET were estimated by Stern–Volmer relation-
ship expressed as kETZ[(FrelK1)/Frel](1/tD); where Frel is
the relative fluorescence intensity of D–S–A dyads
molecules 5 and 7 with respect to those of standards 4 and
6, while tD is the fluorescence lifetime of the latter. The
measurements were performed in five different solvents in
order to examine the effect of solvent and the results are
listed in Table 2. Note that data relevant to compounds
5a/4a and 7a/6a were extracted from our previous report.14
As supported by Table 2, it was apparent that the ET rates
increase upon decreasing the values of DG.
2.3. Electron transfer kinetics
The oxidation potentials of naphthalene moieties were
measured by cyclic voltammetry (see Table 1). The values
obtained for 5a–c agreed with the substituent effect, for
example, 1.27 V for 5c (di-MeO) and 1.78 V for 5b (di-Br).
The reduction potential of ethylene-1,2-dicarboxylate
moiety was estimated to be K1.57 V. These values were
used for evaluating the free-energy (DG) of ET between an
excited-state donor molecule (D*) and a ground-state
acceptor at a defined distance (d) according to Eq. 1:21
Theoretically, upon excitation electron migrates (or tunnels)
from donor to acceptor site via the spacer, forming a charge-
separated ion pair. Charge recombination to the ground state
may result in a low energy emission as the charge-transfer
band (CT band). Our previous analyses have shown that the
decaying rate of fluorescence coincides with the rising
dynamics of the CT band. In many cases, however, the CT
band may not be readily detected due to its weak intensity,
particularly in high polarity solvents such as acetonitrile, in
which the lower energy emission is subject to dominant
radiationless deactivation described by an energy gap law.23
As shown in Figure 4, in contrast to a unique normal
fluorescence for 4d in THF, dual emission was observed in
5d, in which a broad CT band centered at w500 nm was
resolved. CT emissions in other solvents such as dichloro-
methane and ethyl acetate can also be detected, yet in very
DGðdÞ Z EoxðDÞ KEredðAÞ KE00ðDÞ Kðe2=3dÞ
Kðe2=2Þð1=rCD C1=rKA Þð1=37 K1=3Þ
(1)
Table 1. The oxidation potentials and 0–0 band of absorptions
5a/7a
5b/7b
5c/7c
5d/7d
EOX (eV)
E00 (nm)
1.74
317
1.78
330
1.27
326
1.50
335
Table 2. Free energies (DG), relative luminescence quantum yields (Frel) and kET of electron transfer reactions for the dipolar compounds 4–7 in various
solvents
b0
Solvent
t (ns)
DG (eV)
Frel
kET
(!108 sK1
Hel
(cmK1
t (ns)
DG (eV)
Frel
kET
(!108 sK1
Hel
(cmK1
)
b
)
)
)
4aa
41
61
58
37
5a
5a/4ab
0.044
0.020
0.017
0.023
5a
55
83
100
120
5a
1.2
1.8
2.3
2.6
6aa
57
51
57
48
7a
7a/6ab
0.247
0.163
0.012
0.047
7a
0.54
1.01
1.3
7a
7a/5a
0.77
0.73
0.72
0.56
7a/5a
1.01
0.97
0.97
0.78
Et2O
K0.25
K0.37
K0.44
K0.48
K0.17
K0.32
K0.39
K0.44
0.046
0.097
0.125
0.25
EtOAc
THF
CH2Cl2
4.2
4ca
5c
5c/4c
0.104
0.0068
0.0124
0.00104
0.0021
5c
13
246
117
1400
700
5c
—
9.1
6.4
22
17
6c
11
12
12
10
11
7c
0.05
K0.68
K0.75
K0.80
K0.99
7c/6c
0.64
0.35
0.22
0.17
0.18
7c
7c
—
0.58
0.82
1.08
1.08
7c/5c
0.54
0.84
0.61
0.94
0.85
7c/5c
—
0.92
0.68
1.00
0.92
C6H12
EtOAc
THF
CH2Cl2
CH3CN
6.84
5.96
6.78
7.45
6.76
K0.12
K0.74
K0.80
K0.84
K1.00
0.51
1.55
2.95
4.88
4.14
4d
42
40
39
31
25
5d
0.22
K0.40
K0.47
K0.51
K0.67
5d/4d
0.85
0.24
0.08
0.04
0.03
5d
0.04
0.75
2.9
7.8
13
5d
—
0.20
0.44
0.75
1.2
6d
40
39
38
30
41
7d
0.39
K0.35
K0.42
K0.47
K0.66
7d/6d
0.98
0.94
0.93
0.92
0.92
7d
7d
—
0.015
0.018
0.025
0.026
7d/5d
0.35
0.64
0.83
0.92
1.08
7d/5d
—
0.86
1.07
1.13
1.28
C6H12
EtOAc
THF
CH2Cl2
CH3CN
0.005
0.016
0.02
0.03
0.02
The data of compounds 4a, 5a, 6a and 7a were abstracted from Ref. 14.
a Measured by a picasecond dynamic apparatus (Ref. 29); all others by a Hitachi U-3310 spectrophotometer.
b Estimated by the difference of lifetimes, otherwise calculated by relative luminescence quantum yields.

6970
T. J. Chow et al. / Tetrahedron 61 (2005) 6967–6975
involves an electron-coupling matrix element jHelj:
ꢀ
ꢁ
2
2p
ket Z
KðDG ClÞ
2
jHelj exp
(4)
ð4plkBTÞ1=2Z
4lkBT
The value of Hel can be deduced from DG, l, and ket, and
can further, be used as a criteria for judging the effectiveness
of the s-spacer group as a modulator for ET dynamics
according to a superexchange mechanism.24 Figure 5
reveals the plots of log ket versus DG based on all
experimentally available data points of compounds 5 and
7 bearing three kinds of substituents –H (a), –OCH3 (c), and
–Ph (d). Note that the fluorescence intensity of bromo-
substituted derivatives (b) was too weak to have a reliable
value. For the purpose of comparison a simulated curve
(Eq. 4) for 5d in dichloromethane is plotted and shown in
Figure 5. Two noteworthy features can be pointed out from
the scattering pattern of data points depicted in Figure 5: (1)
the ET rates of 5d and 7d are slower than the corresponding
ones of 5a,c and 7a,c by approximately two orders of
magnitude; and (2) the ET rates of all compounds in
cyclohexane seem to be substantially faster than what were
expected. As shown in the plots of Figure 3, the estimated
free energy of ET in nonpolar solvents such as cyclohexane
is either greater or close to zero. Accordingly, the rates of
ET in such solvents (with DGw0) are expected to be
substantially slower than those in polar solvents (cf.
DGwK0.4 eV as shown in Fig. 5). The unexpected high
rate of fluorescence quenching in nonpolar solvents is
intriguing and may be ascribed to the competing processes
associated with electronic energy transfer. Although, the
absorption wavelength of acceptor is apparently shorter than
the emission wavelength of donor, processes of this kind
proceeded in high electronically excited state have been
known previously.25 In polar solvents the comparatively
slow rate of energy transfer is overshadowed by the faster
rate of ET process and is likely to be ignored.
Figure 3. Linear plots of the free energy of ET (DG) versus the reciprocal
of solvent dielectric constant (3) for compounds 5c (B), 7c (C), 5d (,)
and 7d (-), respectively. Points below the line of DGZ0 indicate
exothermic ET processes.
Figure 4. The fluorescence spectra of compounds 4d (dotted line) and 5d
(solid line) in THF. The quenching of fluorescence (378 nm) on 5d is
apparent by the reduction of emission intensity. A broad band appeared on
the right side (495 nm) originating from the emission of charges-separated
species (CT band).
Another salient feature is regarding the slow ET rate for 5d
and 7d, which may be rationalized by a mismatch of orbital
symmetry between donor and acceptor. The magnitude of
low quantum yields. According to Marcus formulation, the
energy gap of CT emission is related to the barrier of nuclear
reorganization (l) during the ET processes. In the case of 5d
in THF, the value of l can be deduced by the following
relationship
l Z DG CE00 KhnCT
(2)
Taking the data of DG and E00 listed in Tables 1 and 2, l
was then deduced to be, for example, w0.75 eV in THF.
The rate constant for a nonadiabatic ET process can be
expressed by Fermi’s golden rule:
2p
2
ket Z
jHelj FC
(3)
Z
where FC is the Franck-Condon factor, that is, the sum of
products of overlap integrals of the vibrational and solvent
wave functions of the reactants with those of the products.
These factors are weighted for the Boltzmann population of
all vibrational energy levels. In the high-temperature limit,
Marcus has provided the following expression, which
Figure 5. Plots of log kET versus DG of compounds 5a (B), 5d (,), 7a
(C), 7c (:), and 7d (&) in different solvents. The ET rates of 5a and 7a
are faster (w102) than the corresponding rates of 5d and 7d. A simulated
curve according to Eq. 4 for 5d in THF (.) is drawn as a reference.

T. J. Chow et al. / Tetrahedron 61 (2005) 6967–6975
6971
electronic coupling between donor and acceptor depends
upon the degree of superexchange interactions, the strength
of which relies not only on the relative orientation between
the donor and acceptor, but also on the corresponding
geometry of spacer group.24 The all-trans s-array is known
to be suitable for modulating electronic interactions.26,27 In
the structure of 5c (Fig. 1), it is clear that the p-face of
naphthalene (D) is held rigidly and parallel to the p-face of
ethylene dicarboxylate (A). Similar geometry is maintained
in the bromo and methoxy substituted derivatives, that is,
5b,c and 7b,c, as evidenced by the high similarity among
their absorption spectra. However, the situation for the
diphenyl substituted derivatives such as 5d and 7d is rather
different, in that the p-orbitals of naphthalene are perturbed
by the free-rotating phenyl groups. Support of this view-
point is rendered by the absorption spectral features of 5d
and 7d, which are distinctively different from those of 5a–c
(not shown here). Likewise, a significant Stokes’ shift is
observed on their emissions. The spectral difference
indicates the presence of conformational variations in both
ground and excited states. We thus, tentatively propose that
the non-planar conformation of naphthalene chromophores
of 5d and 7d reduce the degree of electron coupling between
D and A, and consequently retard the rate of ET processes.
Precise estimation on the electronic coupling element Hel
remains a difficult task. According to Eq. 2 the value of l
can be estimated from the CT emission. It can be divided
into two parts, that is, an internal part li and a solvent
dependent part ls. The value of ls can be estimated by
ls Z e2ð1=rCD C1=rKA K1=dÞð1=n2 K1=3Þ
(7)
where n is the refractive index of the solvent. The value li
can then be obtained from l (Eq. 2) and ls, and is
presumably solvent independent. A reasonable estimation
on li was in the range of 0.10–0.20 eV. This value was taken
for the calculation of Hel by Eq. 4, and the results were listed
in Table 2. Apparently, Hel of !10 cmK1 clearly indicate a
weak coupling and hence, a nonadiabatic ET process in all
cases applied in this study. The averaged b value for these
ladder-shaped spacers was thus, estimated to be about 1.0.
3. Conclusion
In conclusion, the rates of electron transfer were measured
across two types of spacer groups, that is, 1 and 2, where
substituted naphthalene acted as the electron donor and
ethylene-1,2-dicarboxylate as the acceptor. The methoxyl
substituents resonate effectively with the aromatic
p-system, therefore, enrich the electron density of the
donor group. Their ET rates became faster in all solvents
than the one without methoxy substituents. On the contrary,
the presence of phenyl substituents retarded the rates of ET
as judged from the same DG values. The conformational
flexibility of phenyl substituents seem to perturb the well-
aligned symmetry relationship between D and A, resulting
in a reduction of effective electronic coupling. Furthermore,
the free-rotated phenyl substituents render a much wider
Stokes shifts, as well as a substantial band broadening in the
emission spectra.
The value of electronic coupling element Hel is a function of
D–A distance and orientation, as well as the bonding nature
(s or p) and geometry of the spacer. As a trend with similar
structures, its value decreases exponentially with respect to
the edge-to-edge distance (dK2r) between D and A
expressed as
Hel Z He0l exp½Kb0ðd K2rÞꢀ Z He0l exp½Knbꢀ
(5)
where H0el is a value at contact distance 2r for D and A, and
b0 is an attenuation coefficient. The value of Hel usually is
rather difficult to measure accurately. Empirically, the
distance-dependence of ET rate in a specific solvent may be
alternatively expressed by the number of s-bonds (n)
separating D and A:
The free energies of ET were deduced from redox potentials
of both D and A and the 0–0 absorption of D. The
reorganization energy l was estimated according to the
charge transfer emission of 5d (Fig. 4) by Eq. 2.
Accordingly, electronic coupling element Hel was deduced
from DG and l. Comparing the Hel values of systems 1 and
2, the exponential decaying parameter b were computed
according to the relationship of Eq. 5. The values ranging
from 0.6 to 0.9 were not much deviated from analogous
cases published in the literatures. The values reveal the
nature of these linear ladder-shaped oligonorbornyl spacer
groups using as ET modulator, of which the choice is crucial
for a proper design of molecular devices.
kET Z k0 expðK2nb0Þ
(6)
McConnell has calculated the distance dependence of
electronic coupling in a series of a,u-diphenylalkanes and
found the value of b0 to be ca. 2.5.28 Paddon-Row et al. have
measured the ET rates across a series of fused norborna-
diene skeletons. They found out the value of b0 to be in a
range of 0.4–0.63 depending on the solvents.27 These values
complied well with that estimated by Hoffmann,26 and were
much smaller than what were predicted by McConnell.
From the rate constants listed in Table 2, the value of b0 can
be deduced via comparisons between compounds 5 (6
s-bonds between D and A) and 7 (9 s-bonds). For example,
the b value derived from 5a/7a in THF was 0.72 in THF,
whereas those derived from 5c/7c and 5d/7d were 0.61 and
0.83, respectively, (Table 2). It should be noted that these
numbers were neither corrected for distance dependence of
the Franck-Condon factor in Eq. 3, nor the conformational
variations between the structures of 5 and 7. As depicted by
molecular modeling, a change of bending angles between
the p-facial planes of D and A appears to be 608 in 5 (see
Fig. 1) and 08 in 7.
4. Experimental
4.1. General
Infrared spectra were recorded on a Perkin-Elmer 682
infrared spectrophotometer. Elemental analyses were
obtained on a Perkin-Elmer 2400 CHN instrument. Melting
points were measured with a Thomas-Hoover mp apparatus
and are uncorrected. 1H and 13C spectra were obtained on a
Bruker APX-400 spectrometer. Mass spectra were carried

6972
T. J. Chow et al. / Tetrahedron 61 (2005) 6967–6975
out on a VG70-250S spectrometer. Cyclic voltammetry
measurements were performed using a voltammetric
analyzer and a glassy-carbon working electrode in aceto-
nitrile containing 0.1 M tetra-n-butylammonium tetrafluoro-
borate as a supporting electrolyte. Solvents were all of
spectragrade quality. Samples were degassed by three
freeze–pump–thaw cycles in vacuo.
70 eV): m/z (%) 344 (MC, 100), 278 (29), 226 (39), 195 (7),
165 (11). Anal. Calcd for C24H24O2: C, 83.69%; H, 7.02%.
Found: C, 83.49%, H, 7.34%.
4.1.3. 15,16-Diphenylheptacyclo[10.8.1.14,7.03,8.02,9
11,20.013,18]docosa-5,11,13,15,-17,19-hexene (4d). A
.
0
three-neck round bottom flask, fitted with a condenser and
a nitrogen inlet–outlet, was filled with a solution of
compound 4b (1.5 g, 3.4 mmol) in freshly distilled DMF
(100 mL). To it under a nitrogen atmosphere was
added tetrakis(triphenylphosphine)palladium(0) (0.2 g,
0.17 mmol), followed by phenyboronic acid (0.9 g,
7.5 mmol) and a potassium phosphate solution (2 N,
20 mL). The resulted mixture was heated to reflux for
72 h, then was allowed to cool. It was extracted three times
with methylene chloride. The combined organic phase was
dried over anhydrous magnesium sulfate, and concentrated
in vacuo. The product was purified by passing through a
silica gel chromatographic column eluted with hexane/
methylene chloride (5:1) to form colorless solids (0.17 g,
11%), mp 238.6–239.8 8C. IR (KBr): 3021, 2965, 2921,
1653, 1637, 1474, 1458, 1324, 1209, 1187, 1071, 996, 946,
Steady-state absorption and emission spectra were recorded
by a Hitachi (U-3310) spectrophotometer and an Edinburgh
(FS920) fluorimeter, respectively. Details of picosecond
dynamical measurements have been elaborated in the
previous report.29
4.1.1. 15,16-Dibromoheptacyclo[10.8.1.14,7.03,8.02,9
11,20.013,18]docosa-5,11,13,15,-17,19-hexene (4b). A
.
0
two-neck round bottom flask, fitted with a condenser and
a nitrogen inlet–outlet, was filled with a solution of
compound 1 (1.3 g, 7.0 mmol) in freshly distilled DMF
(88 mL). To it was added a,a,a0,a0-hexabromo-o-xylene
(4.5 g, 7.7 mmol), followed by sodium iodide (7.0 g,
47 mmol) in a nitrogen atmosphere. The resulted solution
was heated to 60–70 8C for 20 h, then was poured slowly
into an aqueous solution (350 mL) of sodium bisulfide (5 g).
The mixture was extracted three times with methylene
chloride. The combined organic phase was dried over
anhydrous magnesium sulfate, and concentrated in vacuo.
The product was purified by passing through a silica gel
chromatographic column eluted with hexane/methylene
chloride (5:1) to yield white solids (1.9 g, 62%), mp
223.4–224.4 8C. IR (KBr): 3053, 2970, 2955, 1638, 1619,
1579, 1559, 1466, 1400, 1323, 1273, 1261, 1209, 1190,
1
902, 770, 708, 702 cmK1; H NMR (400 MHz, CDCl3): d
7.77 (s, 2H), 7.55 (s, 2H), 7.16–7.24 (m, 10H), 6.02 (s, 2H),
3.30 (s, 2H), 2.69 (s, 2H), 2.27 (d, 1H, JZ10 Hz), 1.77 (d,
1H, JZ10 Hz), 1.61 (s, 2H), 1.60 (d, 1H, JZ9 Hz), 1.57 (s,
2H), 1.18 (d, 1H, JZ9 Hz); 13C NMR (100 MHz, CDCl3): d
147.2, 141.8, 138.0, 135.8, 132.0, 130.0, 129.3, 127.8,
126.3, 118.3, 46.0, 44.3, 42.2, 42.0, 40.0; MS (EI, 70 eV):
m/z (%) 436 (MC, 100), 370 (45), 317 (47), 241 (15), 165
(3).
1
1101, 947, 928, 898, 885, 703 cmK1; H NMR (400 MHz,
4.1.4. 15,16-Dibromo-6,7-dicarbomethoxyoctacyclo-
[10.10.1.14,9.02,11.03,10.05,8.013,22-.015,20]tetracosa-6,13,
15,17,19,21-hexene (5b). Compound 5b was collected in
78% yield following a similar procedure to that of 5c.
Physical data of 5b: mp 254–256 8C. IR (KBr): 3011, 2954,
2925, 1738, 1717, 1638, 1629, 1463, 1433, 1402, 1267,
CDCl3): d 7.99 (s, 2H), 7.38 (s, 2H), 6.01 (s, 2H), 3.26 (s,
2H), 2.68 (s, 2H), 2.44 (d, 1H, JZ10 Hz), 1.72 (d, 1H, JZ
10 Hz), 1.57 (m, 3H), 1.55 (s, 2H), 1.18 (d, 1H, JZ9 Hz);
13C NMR (100 MHz, CDCl3): d 148.6, 136.4, 133.0, 132.4,
120.9, 118.0, 46.4, 44.8, 42.7, 42.4, 42.3, 40.3; MS (EI,
70 eV): m/z (%) 442 (MC, 100), 376 (54), 323 (15), 243
(15), 163 (15). Anal. Calcd for C22H18Br2: C, 59.76%; H,
4.10%. Found: C, 60.07%, H, 4.36%.
1
1232, 1197, 1136, 1120, 1101, 1050, 929, 896 cmK1; H
NMR (400 MHz, CDCl3): d 8.01 (s, 2H), 7.40 (s, 2H), 3.79
(s, 6H), 3.27 (s, 2H), 2.62 (s, 2H), 2.38 (d, 1H, JZ10 Hz),
2.20 (s, 2H), 1.74–1.77 (m, 4H), 1.62–1.65 (m, 2H), 1.29 (d,
1H, JZ10 Hz); 13C NMR (100 MHz, CDCl3): d 161.5,
147.3, 142.0, 132.5, 131.8, 120.5, 117.5, 51.8, 45.6, 45.6,
43.7, 42.9, 41.8, 36.8, 26.0; MS (EI, 70 eV): m/z (%) 584
(MC, 100), 553 (9), 350 (41), 323 (18), 243 (27), 163 (26).
Anal. Calcd for C28H24Br2O4: C, 57.56%; H, 4.14%. Found:
C, 57.55%, H, 4.11%.
4.1.2. 15,16-Dimethoxyheptacyclo[10.8.1.14,7.03,8.02,9
11,20.013,18]docosa-5,11,13,-15,17,19-hexene (4c). A two-
.
0
neck round bottom flask, fitted with a condenser and a
nitrogen inlet–outlet, was filled with a solution of compound
1 (1.3 g, 7.0 mmol) in freshly distilled DMF (65 mL). To it
was added a,a,a0,a0-hexabromo-4,5-di-methoxy-o-xylene
(3.7 g, 7.7 mmol), followed by sodium iodide (7.0 g,
47 mmol) in a nitrogen atmosphere. The resulted solution
was heated to 60–70 8C for 20 h, then was poured slowly
into an aqueous solution (350 mL) of sodium bisulfide (5 g).
The yellow precipitates were filtered and dried in vacuo. It
was purified by passing through a silica gel chromato-
graphic column eluted with hexane/ethyl acetate (6:1) to
yield white solids (1.6 g, 68%), mp 198.6–199.8 8C. IR
(KBr): 3011, 2957, 2926, 1620, 1507, 1460, 1427, 1248,
4.1.5. 6,7-Dicarbomethoxy-15,16-dimethoxyoctacyclo-
[10.10.1.14,9.02,11.03,10.05,8.013,22.015,20]tetracosa-6,13,
15,17,19,21-hexene (5c). To a two-neck round bottom flask,
fitted with a condenser and a nitrogen inlet–outlet, were
added of compound 4c (100 mg, 0.3 mmol), dimethyl
acetylenedicarboxylate (0.04 mL, 0.3 mmol), and a
catalytic amount of RuH2CO(PPh3)3 in freshly distilled
benzene (10 mL). The resulted solution was stirred with a
magnetic bar for 15 min at ambient temperature, then was
heated to reflux for 24 h. The solvent was evaporated in
vacuo, and the product was purified by passing through a
silica gel chromatographic column eluted with hexane/ethyl
acetate (6:1) to yield white solids (121 mg, 83%), mp 214–
215 8C. IR (KBr): 3007, 2952, 1722, 1627, 1508, 1464,
1144, 1006, 879, 832, 714 cmK1 1H NMR (400 MHz,
;
CDCl3): d 7.38 (s, 2H), 7.05 (s, 2H), 6.01 (s, 2H), 3.95 (s,
6H), 3.23 (s, 2H), 2.67 (s, 2H), 2.22 (d, 1H, JZ9 Hz), 1.71
(d, 1H, JZ9 Hz), 1.52–1.57 (m, 5H), 1.17 (d, 1H, JZ7 Hz);
13C NMR (100 MHz, CDCl3): d 148.8, 145.2, 136.1, 128.0,
117.6, 55.1, 46.1, 44.5, 42.7, 42.6, 42.1, 40.1; MS (EI,

T. J. Chow et al. / Tetrahedron 61 (2005) 6967–6975
6973
1433, 1318, 1251, 1195, 1147, 1050, 1011, 887, 743 cmK1
;
NMR (100 MHz, CDCl3): d 157.9, 135.5, 132.7, 132.0,
129.0, 127.4, 117.6, 46.0, 44.4, 43.6, 42.6, 41.9, 41.6, 41.7,
40.9, 29.1; MS (EI, 70 eV): m/z (%) 534 (MC, 100), 468
(46), 376 (14), 350 (45), 269 (11), 189 (15), 163 (11). Anal.
Calcd for C29H26Br2: C, 65.19%; H, 4.90%. Found: C,
65.46%, H, 5.49%.
1H NMR (400 MHz, CDCl3): d 7.40 (s, 2H), 7.07 (s, 2H),
3.97 (s, 6H), 3.78 (s, 6H), 3.24 (s, 2H), 2.62 (s, 2H), 2.36 (d,
1H, JZ10 Hz), 2.19 (s, 2H), 1.73–1.76 (m, 5H), 1.65 (d, 1H,
JZ11 Hz), 1.27 (d, 1H, JZ11 Hz); 13C NMR (100 MHz,
CDCl3): d 161.8, 148.8, 144.5, 142.3, 128.1, 117.6, 107.0,
56.1, 52.0, 46.0, 45.9, 44.4, 43.3, 42.4, 37.0, 26.2; MS (EI,
70 eV): m/z (%) 486 (MC, 100), 455 (5), 277 (4), 252 (16),
226 (26), 165.1 (4). Anal. Calcd for C30H30O6: C, 74.06%;
H, 6.21%. Found: C, 73.84%, H, 5.97%.
4.1.8. 21,22-Dimethoxydecacyclo[14.10.1.14,13.17,10
2,15.03,14.05,12.06,11.017,26.019,24]hexacosa-8,17,19,21,23,
.
0
25-hexene (6c). Compound 6c was collected in 63% yield
according to a similar procedure to the preparation of 6b.
Physical data of 6c: mp 258.5–259.5 8C. IR (KBr): 2961,
2921, 1621, 1511, 1464, 1426, 1251, 1144, 1005, 884,
The crystal structure of 5c was solved on a Nonius
diffractometer using the q/2q scan method. It was mono-
1
710 cmK1; H NMR (400 MHz, CDCl3): d 7.35 (s, 2H),
˚
clinic in space group C2/c with aZ30.929(7) A, bZ
˚
˚
8.700(1) A, and cZ21.194(3) A, aZ908, bZ
113.466(14)8, gZ908. Crystallographic data has been
deposited with the Cambridge Crystallographic Data Centre
as supplementary publication numbers CCDC 266303.
Copies of the data can be obtained, free of charge, on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK [fax: 144 (0)1223 336033 or e-mail: deposit@ccdc.cam.
ac.uk].
7.04 (s, 2H), 5.91 (s, 2H), 3.95 (s, 6H), 3.17 (s, 2H), 2.59 (s,
2H), 2.31 (d, 1H, JZ10.0 Hz), 1.90 (s, 2H), 1.75 (d, 1H, JZ
9 Hz), 1.70–1.65 (m, 5H), 1.66 (s, 2H), 1.32 (s, 2H), 1.23 (s,
2H), 1.14 (d, 1H, JZ9 Hz); 13C NMR (100 MHz, CDCl3): d
148.5, 144.7, 135.3, 127.8, 117.2, 106.8, 55.8, 45.8, 44.2,
44.0, 42.5, 42.1, 41.8, 41.5, 41.4, 40.7, 28.9; MS (EI,
70 eV): m/z (%) 436 (MC, 100), 370 (15), 277 (4), 252 (15),
226 (15), 165 (4). Anal. Calcd for C31H32O2: C, 85.28%; H,
7.39%. Found: C, 85.28%, H, 7.45%.
4.1.6. 6,7-Dicarbomethoxy-15,16-diphenyloctacyclo-
[10.10.1.14,9.02,11.03,10.05,8.013,22.015,20]tetracosa-6,13,
15,17,19,21-hexene (5d). Compound 5d was collected in
78% yield following a similar procedure to that of 5c.
Physical data of 5d: mp 217.5–219 8C. IR (KBr): 3053,
2965, 2952, 1738, 1720, 1638, 1629, 1474, 1437, 1322,
1298, 1282, 1265, 1228, 1217, 1197, 1133, 1121, 1051, 947,
4.1.9. 21,22-Diphenyldecacyclo[14.10.1.14,13.17,10.02,15
3,14.05,12.06,11.017,26.019,24]hexacosa-8,17,19,21,23,25-
.
0
hexene (6d). A three-neck round bottom flask, fitted with a
condenser and a nitrogen inlet–outlet, was filled with a
solution of compound 6b (2.0 g, 3.7 mmol) in freshly
distilled DMF (100 mL). To it under a nitrogen atmosphere
was added tetrakis(triphenylphosphine)palladium(0)
(0.22 g, 0.185 mmol), followed by phenylboronic acid
(1.0 g, 8.1 mmol) and a potassium phosphate solution
(2 N, 20 mL). The resulted mixture was heated to reflux
for 72 h, then was allowed to cool. It was extracted three
times with methylene chloride. The combined organic phase
was dried over anhydrous magnesium sulfate, and concen-
trated in vacuo. The product was purified by passing through
a silica gel chromatographic column eluted with hexane/
methylene chloride (5:1) to form white solids (0.20 g, 10%),
mp 289–291 8C. IR (KBr): 3052, 2960, 2924, 1600, 1476,
1463, 1443, 1420, 1325, 1261, 1071, 949, 903, 770, 760,
747, 700, 567 cmK1; 1H NMR (400 MHz, CDCl3): d 7.77 (s,
2H), 7.56 (s, 2H), 7.20–7.27 (m, 10H), 5.94 (s, 2H), 3.26 (s,
2H), 2.61 (s, 2H), 2.40 (d, 1H, JZ10 Hz), 1.95 (s, 2H), 1.79
(d, 1H, JZ9 Hz), 1.78–1.72 (m, 5H), 1.72 (s, 2H), 1.39 (s,
2H), 1.38 (s, 2H), 1.15 (d, 1H, JZ8.0 Hz); 13C NMR
(100 MHz, CDCl3): d 1147.1, 142.1, 138.2, 135.5, 132.2,
130.3, 129.5, 128.0, 126.5, 118.4, 46.1, 44.5, 44.1, 42.8,
42.1, 42.0, 41.8, 41.7, 40.9, 29.2; MS (EI, 70 eV): m/z (%)
528 (MC, 100), 462 (11), 370 (5), 344 (30), 318 (15), 241
(5), 165 (1); MS (EI, 70 eV): m/z (%) 528 (MC, 100), 462
(10), 344 (22), 331 (18), 318 (20).
1
905, 770, 748, 700 cmK1; H NMR (400 MHz, CDCl3): d
7.77 (s, 2H), 7.55 (s, 2H), 7.15–7.22 (m, 10H), 3.76 (s, 6H),
3.28 (s, 2H), 2.60 (s, 2H), 2.37 (d, 1H, JZ10 Hz), 2.18 (s,
2H), 1.76–1.77 (d, 5H), 1.62 (d, 1H, JZ11 Hz), 1.26 (d, 1H,
JZ11 Hz); 13C NMR (100 MHz, CDCl3): d 161.5, 146.4,
142.0, 141.8, 138.1, 132.0, 130.0, 129.3, 127.8, 126.3,
118.4, 51.8, 45.7, 44.1, 43.3, 41.9, 36.8, 26.0; MS (EI,
70 eV): m/z (%) 578.1(MC, 100), 547.1 (4), 344.1 (31),
318.1 (30), 241.1 (5), 165.1 (1). Anal. Calcd for C40H34O4:
C, 83.02%; H, 5.92%. Found: C, 82.78%, H, 6.00%.
4.1.7. 21,22-Dibromodecacyclo[14.10.1.14,13.17,10.02,15
3,14.05,12.06,11.017,26.019,24]hexacosa-8,17,19,21,23,25-
.
0
hexene (6b). A two-neck round bottom flask, fitted with a
condenser and a nitrogen inlet–outlet, was filled with a
solution of compound 2 (1.9 g, 7.0 mmol) in freshly distilled
DMF (95 mL). To it was added a,a,a0,a0-hexabromo-o-
xylene (4.5 g, 7.7 mmol), followed by sodium iodide (7.0 g,
47 mmol) in a nitrogen atmosphere. The resulted solution
was heated to 60–70 8C for 20 h, then was poured slowly
into an aqueous solution (350 mL) of sodium bisulfide (5 g).
The mixture was extracted three times with methylene
chloride. The combined organic phase was dried over
anhydrous magnesium sulfate, and concentrated in vacuo.
The product was purified by passing through a silica gel
chromatographic column eluted with hexane/methylene
chloride (5:1) to yield white solids (2.2 g, 60%), mp 289–
291 8C. IR (KBr): 3048, 2963, 2930, 1631, 1583, 1464,
1402, 1326, 1266, 1225, 1102, 949, 928, 896, 715 cmK1; 1H
NMR (400 MHz, CDCl3): d 8.01 (s, 2H), 7.38 (s, 2H), 5.93
(s, 2H), 3.22 (s, 2H), 2.61 (s, 2H), 2.36 (d, 1H, JZ10 Hz),
1.93 (s, 2H), 1.77–1.65 (m, 4H), 1.68 (s, 2H), 1.62 (s, 2H),
1.38 (s, 2H), 1.35 (s, 2H), 1.16 (d, 1H, JZ8.2 Hz); 13C
4.1.10. 9,10-Dibromo-23,24-dicarbomethoxyundeca-
.
cyclo[16.10.1.14,15.121,26.02,17.03,16.05,14.07,12.019,28.020,27
0
22,25]octacosa-5,7,9,11,13,23-hexene (7b). Compound 7b
was collected in 78% yield following a similar procedure to
that of 5c. Physical data of 7b: mp 319.5–321.0 8C. IR
(KBr): 2951, 2927, 1740, 2719, 1627, 1618, 1559, 1435,
1267, 1232, 1197, 1138, 1124, 1100, 1049, 929, 896,
670 cmK1; 1H NMR (400 MHz, CDCl3): d 8.0 (s, 2H), 7.38
(s, 1H), 3.78 (s, 6H), 3.22 (s, 2H), 2.51 (s, 2H), 2.35 (d, 1H,

6974
T. J. Chow et al. / Tetrahedron 61 (2005) 6967–6975
H. Q. N.; Gunnlaugsson, T.; Huxley, A. J. M.; McCoy,
C. P.; Rademacher, J. T.; Rice, T. E. Chem. Rev. 1997, 97,
1515–1566.
JZ10 Hz), 2.10 (s, 2H), 1.58–1.92 (m, 14H), 1.30 (d, 1H,
JZ11 Hz); 13C NMR (100 MHz, CDCl3): d 161.8, 147.8,
142.2, 132.7, 132.0, 120.6, 117.6, 52.0, 46.0, 45.8, 44.81,
44.2, 43.7, 42.2, 42.0, 41.7, 37.0, 29.2, 26.2; MS (EI,
70 eV): m/z (%) 676 (MC, 100), 645 (8), 442 (8), 376 (9),
350 (34), 323 (11), 243 (16), 163 (8). Anal. Calcd for
C35H32Br2O4: C, 62.15%; H, 4.77%. Found: C, 62.29%, H,
4.89%.
3. (a) Yu, C. J.; Chong, Y.; Kayyem, J. F.; Gozin, M. J. Org.
Chem. 1999, 64, 2070–2079. (b) Lewis, F. D.; Wu, T.; Zhang,
Y.; Letsinger, R. L.; Greenfield, S. R.; Wasielewski, M. R.
Science 1997, 277, 673–676.
4. (a) Gust, D.; Moore, T. A.; Moore, A. L. Acc. Chem. Res. 1993,
26, 198–205. (b) Roest, M. R.; Verhoeven, J. W.; Schudde-
boom, W.; Warman, J. M.; Lawson, J. M.; Paddon-Row, M. N.
J. Am. Chem. Soc. 1996, 118, 1762–1768.
4.1.11. 23,24-Dicarbomethoxy-9,10-dimethoxyundeca-
.
cyclo[16.10.1.14,15.121,26.02,17.03,16.05,14.07,12.019,28.020,27
0
22,25]octacosa-5,7,9,11,13,23-hexene (7c). Compound 7c
5. Boyd, R. W. Nonlinear Optics; Academic: New York, 1992.
Prasad, P. N.; Williams, D. J. Introduction to Nonlinear
Optical Effects in Molecular and Polymers; Wiley: New York,
1991.
was collected in 78% yield following a similar procedure to
that of 5c. Physical data of 7c: mp 306.5–308.5 8C. IR
(KBr): 2953, 2921, 1727, 1625, 1506, 1466, 1430, 1321,
1249, 1196, 1143, 1046, 1008, 880 cmK1 1H NMR
;
6. (a) Chattoraj, M.; Paulson, B.; Shi, Y.; Closs, G. L.; Levy,
D. H. J. Phys. Chem. 1994, 98, 3361–3368. (b) Chattoraj, M.;
Bal, B.; Closs, G. L.; Levy, D. H. J. Phys. Chem. 1992, 95,
9666–9673.
(400 MHz, CDCl3): d 7.35 (s, 2H), 7.04 (s, 2H), 3.94 (s,
6H), 3.75 (s, 6H), 3.15 (s, 2H), 2.48 (s, 2H), 2.29 (d, 1H, JZ
10 Hz), 2.07 (s, 2H), 1.87 (s, 2H), 1.87–1.80 (m, 2H), 1.71
(d, JZ10 Hz, 1H), 1.70 (s, 2H), 1.70–1.69 (m, 1H), 1.58 (s,
2H), 1.55 (s, 2H), 1.53 (s, 2H), 1.27 (d, 1H, JZ11 Hz); 13C
NMR (100 MHz, CDCl3): d 161.2, 148.7, 144.6, 142.1,
127.9, 117.4, 106.9, 55.9, 51.9, 45.9, 45.7, 44.7. 44.1, 44.1,
42.2, 42.2, 41.6, 36.9, 29.0, 26.1; MS (EI, 70 eV): m/z (%)
578 (MC, 100), 547 (4), 344 (2), 252 (15), 226 (18), 165
(16). Anal. Calcd for C37H38O6: C, 76.79%; H, 6.62%.
Found: C, 76.71%, H, 6.70%.
7. Balzani, V.; Juris, A.; Venturi, M. Chem. Rev. 1996, 96,
759–834.
8. Zimmerman, H. E.; Goldman, T. D.; Hirzel, T. K.; Schmidt,
S. P. J. Org. Chem. 1980, 45, 3933–3951.
9. (a) Tung, C. H.; Zhang, L. P.; Li, Y.; Cao, H.; Tanimoto, Y.
J. Am. Chem. Soc. 1997, 119, 5348–5254. (b) Agyin, J. K.;
Timberlake, L. D.; Morrison, H. J. Am. Chem. Soc. 1997, 119,
7945–7953.
10. Warrener, R. N. Eur. J. Org. Chem. 2000, 3363–3380.
11. Warrener, R. N.; Pitt, I. G.; Butler, D. N. J. Chem. Soc., Chem.
Commun. 1983, 1340–1341.
4.1.12. 23,24-Dicarbomethoxy-9,10-diphenylundeca-
.
0
cyclo[16.10.1.14,15.121,26.02,17.03,16.05,14.07,12.019,28.020,27
22,25]octacosa-5,7,9,11,13,23-hexene (7d). Compound 7d
12. Warrener, R. N.; Abbenante, G.; Kennard, C. H. L. J. Am.
Chem. Soc. 1994, 116, 3645–3636.
was collected in 78% yield following a similar procedure to
that of 5c. Physical data of 7d: mp 294.5–296 8C. IR (KBr):
3060, 2950, 2922, 1736, 1719, 1632, 1598, 1474, 1436,
1322, 1267, 1232, 1208, 1198, 1049, 966, 949, 904, 770,
13. (a) Chiou, N. R.; Chow, T. J.; Chen, C. Y.; Hsu, M. A.; Chen,
H. C. Tetrahedron Lett. 2001, 42, 29–31. (b) Chow, T. J.; Hon,
Y. S.; Chen, C. Y.; Huang, M. S. Tetrahedron Lett. 1999, 40,
7799–7801.
1
742, 697 cmK1; H NMR (400 MHz, CDCl3): d 7.76 (s,
14. Chen, K.-Y.; Chow, T. J.; Chou, P.-T.; Cheng, Y.-M.; Tsaia,
S.-H. Tetrahedron Lett. 2002, 43, 8115–8119.
2H), 7.52 (s, 2H), 7.17–7.19 (m, 10H), 3.76 (s, 6H), 3.22 (s,
2H), 2.49 (s, 2H), 2.34 (d, 1H, JZ10 Hz), 2.08 (s, 2H), 1.89
(s, 2H), 1.89–1.80 (m, 2H), 1.73–1.70 (m, 2H), 1.70 (s, 2H),
1.59 (s, 2H), 1.56 (s, 4H), 1.27 (d, 1H, JZ11 Hz); 13C NMR
(100 MHz, CDCl3): d 161.6, 146.7, 142.0, 141.8, 138.0,
132.0, 130.0, 129.3, 127.8, 126.3, 118.2, 51.8, 45.9, 45.6,
44.6, 44.0, 43.9, 42.1, 41.9, 41.5, 36.8, 28.9, 26.0; MS (EI,
70 eV): m/z (%) 670 (MC, 100), 639 (3), 436 (1), 370 (5),
344 (14), 318 (11), 241 (3).
15. (a) Hieber, W.; Sedlmeier, J. Chem. Ber. 1954, 87, 789. (b)
Arnold, D. R.; Trecker, D. J.; Whipple, E. B. J. Am. Chem. Soc.
1965, 87, 2596–2602.
16. (a) Paddon-Row, M. N.; Patney, H. K. Synthesis 1986,
328–330. (b) Cava, M. P.; Deana, A. A.; Muth, K. J. Am.
Chem. Soc. 1959, 81, 6458–6460. (c) Mcomie, J. F. W.; Perry,
D. H. Synthesis 1973, 416–417.
17. (a) Miyaura, N.; Yanagi, T.; Suzuki, A. Synth. Commun. 1981,
11, 513–519. (b) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95,
2457–2483.
Acknowledgements
18. (a) Ahmad, N.; Levison, J. J.; Robinson, S. D.; Uttley, M. G.
Inorg. Synth. 1974, 15, 45–64. (b) Kumar, K.; Tepper, R. J.;
Zeng, Y.; Zimmt, M. B. J. Org. Chem. 1995, 60, 4051–4066.
19. Platt, J. R. J. Chem. Phys. 1949, 17, 484–495.
Supports from Academia Sinica and the National Science
Council of Taiwan are gratefully acknowledged.
˘
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