Selective and gram-scale synthesis of [8]cycloparaphenylene

Article abstract of DOI:10.1021/acs.joc.9b02844

Selective and large-scale synthesis of [8]cycloparaphenylene (CPP) was achieved in seven steps starting from commercially available 4-bromo-4′-hydroxybiphenyl and 4,4′-dibromobiphenyl. The key unsymmetrical tetraring unit, 4-bromophenyl and 4′-bromobiphenyl-substituted cis-1,4-bis(triethylsiloxy)-2,5-cyclohexadiene-1,4-diyl (5fA), was synthesized on an ～50 g scale by stereoselective cis-addition of 4-bromo-4′-lithiobiphenyl to 4-(4-bromophenyl)-4-hydroxy-2,5-cyclohexadien-1-one, which was synthesized on an ～100 g scale. Platinum-mediated selective dimerization of the four-ring unit 5fB and subsequent reductive aromatization of the cyclohexadiene-diyl by H₂SnCl₄ gave 2 g of [8]CPP in 6.6% overall yield (10.2% on small scale).

Full text of DOI:10.1021/acs.joc.9b02844

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Article
Selective and Gram-Scale Synthesis of [8]Cycloparaphenylene
Tatsuya Kawanishi, Kosuke Ishida, Eiichi Kayahara, and Shigeru Yamago
J. Org. Chem., Just Accepted Manuscript • Publication Date (Web): 12 Jan 2020
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Selective and Gram-Scale Synthesis of
[8]Cycloparaphenylene
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Tatsuya Kawanishi,† Kosuke Ishida,‡ Eiichi Kayahara,‡* and Shigeru Yamago‡*
†Oji R&D Center, Tokyo Chemical Industry Co., LTD., Toshima, Kita-ku, Tokyo 114-0003, Japan
‡Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
KEYWORDS. Cycloparaphenylene, Macrocycles, Platinum, Tin, Reductive aromatization
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ABSTRACT. A selective and large-scale synthesis of [8]cycloparaphenylene (CPP) was achieved
in seven steps starting from commercially available 4-bromo-4’-hydroxybiphenyl and 4,4’-
dibromobiphenyl. The key unsymmetrical tetraring unit, 4-bromophenyl and 4’-bromobiphenyl-
substituted cis-1,4-bis(triethylsiloxy)-2,5-cyclohexadiene-1,4-diyl (5fA), was synthesized on an
~50 g scale by stereoselective cis-addition of 4-bromo-4’-lithiobiphenyl to 4-(4-bromophenyl)-4-
hydroxy-2,5-cyclohexadien-1-one, which was synthesized on an ~100 g scale. Platinum-mediated
selective dimerization of the four-ring unit 5fB and subsequent reductive aromatization of the
cyclohexadiene-diyl by H2SnCl4 gave 2 g of [8]CPP in 8.8% overall yield.
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Introduction
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Hoop-shaped -conjugated macrocycles have garnered immense interest due to their unique
topological structure, physical properties, and potential applications in molecular electronics.1-4
[N]Cycloparaphenylenes ([N]CPPs, Figure 1), which consist of para-linked N phenylene units
forming a cyclic structure corresponding to the simplest structural unit of armchair carbon
nanotubes (CNTs), occupy the central position among such macrocycles after the first synthesis
of [9], [12], and [18]CPPs by Bertozzi and Jasti in 2008.5 With the significant endeavors by Itami,6
Yamago,7 Jasti,8 and others,9-17 CPPs with different sizes ([5]-[16], [18], [20], and [21]CPPs), 18-
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21,22-25,26-33
various CPP derivatives,12, 13, 15, 16, 34-46 and structurally related cyclic conjugated
macrocycles10, 14, 47-51 have also been synthesized to date. Moreover, the unique properties of CPPs,
such as photophysical properties,52, 53 redox properties,26, 54-62 and host–guest chemistry,63-71 have
been intensively studied. Furthermore, applications of these conjugated macrocycles to organic
devices have emerged.17, 46, 72, 73 With these advances in CPP chemistry and materials science, the
demand for the availability of CPPs in quantity has been increasing. While large-scale synthesis
(>0.5 g scale) of [5],30 [6],31 [8],19 [10],19, 32 and [12]CPPs22 has already been reported, the
development of a more efficient synthetic route is still lacking.
Figure 1. Structure of [N]CPPs.
[8]CPP is a unique CPP with characteristic yellow-green fluorescence with a moderate quantum
yield (8%).7 CPPs larger than [9]CPPs emit blue fluorescence with high quantum yields,52 but
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[7]CPP emits orange fluorescence with a very low quantum yield (0.7%).8 No fluorescence was
observed for [6] and [5]CPPs.20, 21, 28, 29 Furthermore, a recent time-resolved spectroscopic study
revealed that [8]CPP possesses the longest life time of the S1 state among [5]-[12]CPPs.74 These
results suggest that [8]CPP is located at the inflection point in the photophysical properties of CPPs.
Therefore, increasing the availability of [8]CPP would further stimulate the elucidation of its
interesting properties and lead to the development of [8]CPP-based materials through, for example,
its chemical functionalization.
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[8]CPP was synthesized for the first time by Yamago by using the platinum-mediated
cyclotetramerization of 4,4’-bistrimethylstannylbiphenyl (Scheme 1a).7 The overall yield was 57%
after the optimization,75 but the requirement for four equivalents of platinum and the low solubility
of the platinum intermediate limited the large-scale synthesis. Jasti reported the gram-scale
synthesis of [8]CPP based on the coupling reaction of three-ring unit 1a and five-ring unit 2a (R
= Me) having cis-1,4-dimethoxy-2,5-cyclohexadiene-1,4-diyl groups to yield macrocycle 3a
(Scheme 1b).3 Reductive aromatization of the dimethoxy-2,5-cyclohexadiene-1,4-diyl moieties in
3a by sodium naphthalenide afforded [8]CPP. More than 1 g of [8]CPP was obtained in 3.1%
overall yield from the commercially available 4-bromo-4’-hydroxybiphenyl. Yamago reported the
modification of this method using bis(triethylsilyloxy [TES]) derivatives 1b and 2b (R = SiEt3) as
the coupling partners and applying H2SnCl4-mediated reductive aromatization of 3b to give
[8]CPP in 4.8% overall yield.30 Itami also reported the coupling reaction of seven-ring unit 4 and
1,4-phenylenediboronic acid followed by oxidative dehydration, but the scale and yield were low
(<1 % overall yield, Scheme 1c).25
Here, we report a new and scalable synthesis of [8]CPP (Scheme 1d). The method is based on
our gram-scale synthesis of [6]CPP through the platinum-mediated dimerization of 5c (x, y =
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Scheme 1. a-c) Previous synthetic routes of [8]CPP. d) Previous synthesis of [6], [10], and
[14]CPPs and new synthetic route for [8]CPP. cod = 1,5-cyclooctadiene, pin = pinacolato, MOM
= methoxymethyl.
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1).31 Although one-step cyclization of 5c by Yamamoto coupling employing a Ni(0) complex gave
a mixture of cyclic dimer 6c, trimer, and tetramer, the reaction of 5c and PtCl2(cod) (cod = 1,5-
cyclooctadiene) selectively and exclusively afforded dimer 6c, from which the reductive
elimination of platinum and reductive aromatization of the 1,4-cyclohexadiene groups by H2SnCl4
yielded gram quantities of [6]CPP. The method was recently applied to the synthesis of [10]CPP32
and [14]CPP33 through the platinum-mediated selective dimerization of 5d (x, y = 2) and 5e (x, y
= 3), respectively. The method is highly reliable for the synthesis of cyclic dimers of 5 derivatives,
and various substituted [10]CPP derivatives have been synthesized by this method on the gram
scale.32 However, the method is applicable for the synthesis of [2(2x +1)]CPPs only when the
numbers of phenylene units x and y are equal. If we can use an unsymmetrical precursor with
different values of x and y, the method would become more versatile. Here, we report the synthesis
[8]CPP based on the dimerization of unsymmetrical precursor 5f (x = 1, y = 2) as a proof of
principle of this synthetic route. Furthermore, the generality of this method was evaluated by
synthesizing fluorene-embedded [8]CPP.
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Results and Discussion
The synthesis started from commercially available 4-bromo-4’-hydroxybiphenyl, which was
transformed to 4-(4-bromophenyl)-4-hydroxy-2,5-cyclohexadien-1-one (7)19 in two steps on a 100
g scale by modifying the method reported by Jasti19 (Scheme 2). Then, 7 was converted to TES-
protected 5fA (M = Br) in one pot in 56% yield through protection of the hydroxyl group of 7 as
a sodium salt by treatment with NaH (1.3 equiv), addition of 4-bromo-4′-lithiobiphenyl prepared
in situ from 4,4′-dibromobiphenyl (8, 2.1 equiv) and BuLi (2.2 equiv), and trapping of the resulting
bis-alkoxide with TES chloride (3.0 equiv). NMR analyses suggest the exclusive formation of the
cis isomer (>90% selectivity). 4-Bromo-4′-lithiobiphenyl was generated from 4-bromo-4′-
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iodobiphenyl in a previous report,32 and we found that dibromo precursor 8, which has higher
availability than 4-bromo-4’-iodobenzene, was successfully used with equal efficiency. Then, 5fA
was converted into bis-boronate 5fB (X = B[pin]) through a twofold bromine-borane exchange
reaction. Nearly 40 g of 5fB was isolated by silica gel chromatography in 76% yield.
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Scheme 2. Synthesis of [8]CPP
The feasibility of the new synthetic route was first examined on a small scale. Thus, a mixture
of 5fB (0.20 mmol) and PtCl2(cod) (1.0 equiv) in the presence of K3PO4 (5.0 equiv) in THF was
heated at 65 °C for 20 h, and the desired cyclic dimer 6f was isolated in 62% yield by preparative
gel permeation chromatography (GPC). While nearly 20% of linear oligomers were separated, no
cyclic oligomers other than 6f were detected. The structure of 6f was estimated at first by 1H NMR
measured in CDCl3; the protons of the cyclohexadiene groups appeared at  = 5.81 and 5.99 ppm
as two doublets (3JH-H = 10.0 Hz), and those of the paraphenyl groups were observed at  = 6.99,
7.08, 7.18, 7.29, 7.33, and 7.33 ppm as doublets (3JH-H = 8.0-8.4 Hz). The olefinic protons of the
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cod ligand were observed at 5.21 and 5.08 ppm as singlets with a 195Pt satellite (2JPt-H = 43 and 56
Hz, respectively), and the methylene protons appeared at approximately 2.54 ppm as broad peaks.
In the 13C NMR spectrum, twelve and four signals corresponding to the carbon atoms of the
paraphenyl and cyclohexadiene groups, respectively, were observed. The observed spectra are
consistent with the C2h structure of 6f. In the electrospray ionization time-of-flight mass spectra
(ESI-TOF MS), the molecular ion mass of 6f was observed as sodium ion adducts.
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The reductive elimination of platinum from 6f in the presence of PPh3 (5.0 equiv) afforded
cyclic dimer 9 in 77% yield after silica gel chromatography. The highly symmetric D2h structure
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of 9 was suggested by H NMR spectroscopy; the protons of the cyclohexadiene and the central
paraphenyl rings in the terphenyl bridge appear at 6.33 and 7.16 ppm, respectively, as singlets, and
those of the paraphenylene rings connected to the 1,4-cyclohexadiene groups appear at 6.95 and
7.00 ppm (3JH-H = 8.8 Hz) as two doublets. The observed high magnetic field resonance of the
latter signals is due to the deshielding effect of the facing paraphenyl rings. Indeed, the optimized
structure of the free alcohol form of 9 by density functional theory (DFT) calculations at the rings
connecting to the 1,4-cyclohexadiene groups are located 3.51 and 4.42 Å from the centroid
Figure 2. Optimized structure of the free alcohol form of 9 calculated by DFT calculation at the
B3LYP/6-31G(d) level of theory. Gray, white, and red represent carbon, hydrogen, and oxygen
atoms.
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B3LYP/6-31G(d) level of theory suggests that the two protons (H1 and H2) of the paraphenylene
of the facing paraphenyl group, respectively (Figure 2). These distances are consistent with the
deshielding effect of H1 and H2 observed in the 1H NMR.
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Next, the same reaction was repeated on a large scale by starting from 50.0 g of 5fB (60.9 mmol)
and PtCl2(cod) (22.8 g, 60.9 mmol) in the presence of K3PO4 (64.7 g, 0.305 mol) in THF (4.0 L)
at 65 °C for 46 h. The crude reaction mixture containing 6f was directly used for the next step
without purification, and the reductive elimination of platinum at 105 °C by adding PPh3 gave 10.7
g of 9 in 31% yield (two steps).
Reductive aromatization of 9 (5.80 g, 5.12 mmol) was successfully carried out by employing
H2SnCl4 (4.4 equiv)30 prepared in situ from SnCl2 and HCl (2.0 equiv) in THF at room temperature
for 18 h, and 1.97 g of [8]CPP was isolated by silica gel chromatography in 67% yield. The overall
yield was 8.8% in 7 steps with 6 pots from the commercially available 4-bromo-4’-
hydroxybiphenyl. While purification of the intermediate and final product by silica gel
chromatography was still needed, this synthetic route significantly improved the previous gram-
scale synthesis of [8]CPP.
To clarify the advantage of platinum-mediated dimerization, one-step cyclization of 5fA was
investigated under the Ni(0)-mediated Yamamoto coupling reaction condition by treatment with
Ni(cod)2 and 2,2’-bipyridyl (Scheme 3). Cyclic trimer 10 was formed as the major product in 34%
yield, and the desired dimer 9 was obtained in only 21% yield. As 10 and 9 could be separated by
preparative GPC and 10 could be transformed to [12]CPP in high yield by H2SnCl4-mediated
reductive aromatization, the method can be utilized for the random synthesis of [8] and [12]CPPs.
Despite the usefulness of the random synthesis for increase the availability of CPPs with different
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size, however, the method is limited to the small scale synthesis due to the use of preparative GPC
for the separation. Therefore, the platinum-mediated method is suitable for obtaining [8]CPP with
high efficiency and selectivity.
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Scheme 3. One-step cyclization of 5fA
Finally, the generality of the new protocol was examined by the synthesis of fluorene-embedded
[8]CPP 11 (Scheme 4). The asymmetric unit 12 was synthesized by the addition of 2-bromo-9,9-
dibutyl-7-lithio-9H-fluorene, which was in situ generated from 2,7-dibromo-9,9-dibutyl-9H-
fluorene (13) and BuLi, to a sodium salt of 7 and subsequent TES protection gave 12A with high
cis selectivity in 64% yield. After bromine-borane transformation from 12A to 12B, the reaction
of 12B and PtCl2(cod) in the presence of K3PO4 gave the bis-platinum complex 14 in 71% yield
along with ca. 15% of linear oligomers. 14 consists of a 50:50 mixture of syn and anti rotamers
with respect to the relative orientation of the fluorene unit. Highly selective synthesis of 14 is in
sharp contrast to our previous attempts to synthesize CPPs through a rectangular shaped platinum
complex having platinum atom at each corner,26 which resulted in low yield of the desired product.
The difference most likely comes from the rigid structure of 1,4-cyclohexadiene unit in 14
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compared to the platinum atom for making curvature required for the synthesis of cyclic complexes.
The mixture of syn and anti isomers of 14 was subjected to the reductive elimination of platinum
giving a 58:42 mixture of two rotamers of cyclic dimer 15. Reductive aromatization of 15 by
H2SnCl4 afforded the desired 11 as a 61:39 mixture of syn and anti isomers in 81% combined yield.
The syn/anti ratio of both 15 and 11 did not change after heating at 150 °C for 12 h in CD2Cl4.
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Bu Bu
(cod)
Pt
Bu
Bu
Br
Br
OSiEt3
OSiEt3
13
Et3SiO
Et3SiO
(2.1 equiv)
13
BuLi (1.1 equiv to
THF, -78 °C, 1 h
)
Bu
Bu
M
Bu Bu
Li
Br
Et3SiO
1)
Bu
Pt
(cod)
Bu
NaH
Pt
Cl2(cod) (1.0 equiv)
K3PO4 (5.0 equiv)
THF, -78 °C, 2 h
(1.3 equiv)
14
syn-
7
THF
65 °C, 24 h
71%
THF
-78 °C, 1 h
2) Et3SiCl (3.0 equiv)/DMF
THF, -50 °C to rt, 12 h
(cod)
Pt
Bu
Et3SiO
Bu
64%
14/
14
(syn- anti- = 50/50)
M
OSiEt3
OSiEt3
12
: M = Br
: M = Bpin
Et3SiO
Et3SiO
1) BuLi (2.4 equiv),
THF, -78 °C, 0.5 h
2) iPrOBpin (3.0 equiv)
-78 °C to rt, 6 h
87%
A
B
Bu
14
Pt
(cod)
Bu
Bu
Bu
anti-
Bu
Bu
OSiEt3
OSiEt3
Et3SiO
Et3SiO
Bu
15
Bu
Bu
Bu
H2SnCl4 (4.4 equiv)
PPh3 (5.0 equiv)
11
syn-
syn-
THF
rt, 6 h
81%
toluene
105 °C, 18 h
72%
Bu
Bu
Bu
Bu
11/
11
(syn- anti- = 61/39)
(Isomer ratio = 58/42)
OSiEt3
Et3SiO
OSiEt3
Et3SiO
Bu
Bu
Bu
11
anti-
Bu
15
anti-
Scheme 4. Synthesis of fluorene-embedded [8]CPP 11
The stability of the syn and anti isomers of 15 and 11 was estimated by the DFT calculation for
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the model compounds of 15, tetraol (OH group instead of OTES group) of bis-dimethylfluorene-
embedded derivative, and 11, bis-dimethylfluorene derivative, at the B3LYP/6-31G* level of
theory. The results indicates that the anti isomer is slightly thermodynamically more stable than
the syn isomer by 6.1 kJ mol-1 for 15, whereas the syn isomer is significantly more stable than the
anti isomer by 15 kJ mol-1 for 11. The results would suggest that the enrichment of the syn isomer
in 11 is due to the isomerization during the transformation from 15 to 11 or the difference in the
efficiency of conversion from anti and syn isomers of 15 to the corresponding isomers of 11.
Further studies are needed to clarify this point.
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In summary, [8]CPP was synthesized on a gram scale in 7 steps through the platinum-mediated
dimerization of unsymmetrical four-ring unit 5fB and H2SnCl4-mediated reductive aromatization.
We believe that the current method opens new possibilities to design and synthesize various CPP
derivatives and structurally diverse macrocycles in a highly selective and efficient manner.
Experimental Section
General. All reactions involving air- and moisture-sensitive compounds were carried out in a dry
reaction vessel under nitrogen atmosphere. An oil bath was used to elevate the temperature of
reactions. Preparative GPC was performed on JAIGEL 1H, 2H, and 2.5H polystyrene columns
(Japan Analytical Industry Co., Ltd.) with CHCl3 as the eluent. 1H (400 MHz) and 13C{1H} (100
MHz) NMR spectra were obtained for a CDCl3 solution of the samples and are reported asin
units of parts per million (ppm) from an internal tetramethylsilane or a residual solvent peak. The
electrospray ionization (ESI)-TOF MS spectrum was recorded on a spectrometer in positive or
negative mode. A sample was injected as a CH2Cl2/methanol or acetonitrile solution. The matrix-
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assisted laser-desorption ionization (MALDI)-TOF MS spectrum was obtained on a spectrometer
in positive reflection mode at an acceleration voltage of 20 kV. Samples were prepared from a
THF solution by mixing a sample (1 mg mL-1) and dithranol (10 mg mL-1) in a 1:1 ratio. Infrared
(IR) spectroscopy was reported in cm-1. Melting point (mp) was measured and was uncorrected.
Materials. Unless otherwise noted, commercially available materials were used without
purification. Chlorotrimethylsilane was distilled just before use. The water content in the solvents
was determined by a Karl-Fisher water titrater. Compound 7 was synthesized by modifying the
literature method.19 PtCl2(cod) and 1376 were synthesized according to literature procedures.77
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Synthesis of 4-(4-bromophenyl)-4-hydroxycyclohexa-2,5-dien-1-one (7). To a slurry of 4-
bromo-4’-hydroxybiphenyl (100 g, 401 mmol) and imidazole (32.8 g, 481 mol) in CH2Cl2 (150
mL) was added chlorotrimethylsilane (55.8 mL, 441 mmol) over 30 min at 0 °C, and the resulting
mixture was slowly warmed to room temperature. After stirring for 10 h at 0 °C, the reaction
mixture was quenched with a saturated aqueous NaHCO3 solution and extracted with CH2Cl2. The
combined organic layers were washed with saturated brine solution and dried over Na2SO4, filtered
and concentrated to give 4-bromo-4’-[(trimethylsilyl)oxy]-1,1’-biphenyl quantitatively (129 g) as
a colorless solid. [Acetyloxy(phenyl)-λ3-iodanyl] acetate (PhI(OAc)2, 155 g, 481 mmol) and the
above-obtained biphenyl were alternatively added to a mixture of THF (2.00 L), CH3CN (500 mL)
and H2O (500 mL) over the course of 3 h at room temperature. After stirring for an additional 12
h at room temperature, the reaction mixture was quenched with saturated aqueous NaHCO3
solution and extracted with CH2Cl2. The combined organic layer was washed with a saturated
aqueous NaCl solution, dried over Na2SO4, filtered and concentrated under reduced pressure to
give a crude mixture. The residue was washed with dibutyl ether to give 7 as a colorless solid in
80% yield (84.9 g). The NMR spectra were consistent with literature data.19
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Synthesis
of
[1-[4-bromo-(1,1'-biphenyl)-4’-yl]-4-(4-bromophenyl)-4-
8
9
triethylsilyloxycyclohexa-2,5-dien-1-yl]oxy-triethylsilane (5fA). A solution of 7 (30.0 g, 0.113
mol) in 240 mL of THF was added slowly to a slurry of sodium hydride (5.88 g, 0.147 mol, 60%
in mineral oil) in 300 mL of THF over 0.5 h at -78 °C through a dropping funnel, and the resulting
mixture was stirred for 1 h at the same temperature. In a separate flask, BuLi (156 mL, 1.6 M in
hexane, 0.249 mol) was added slowly to a solution of 4,4’-dibromobiphenyl (74.1 g, 0.238 mol)
in THF (750 mL) at -78 °C using a dropping funnel. After stirring for 1 h at the same temperature,
the resulting 4-bromo-4′-lithiobiphenyl was added through a cannula to the above-prepared
solution containing 7 at -78 °C. After stirring for 2 h at the same temperature, DMF (120 mL) and
TES chloride (51.2 g, 0.340 mol) were added to the solution at approximately -50 °C. After stirring
overnight at room temperature, the reaction mixture was quenched with crushed ice and a saturated
aqueous NaHCO3 solution and extracted with ethyl acetate. The combined organic layer was
washed with a saturated aqueous NaCl solution, dried over Na2SO4, filtered and concentrated
under reduced pressure to give a crude mixture. Purification by silica gel chromatography
(hexane/toluene = 100/0, 20/1 to 9/1) afforded 5fA as a colorless gummy oil in 56% yield (46.2
g).
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1H NMR (CDCl3, 400 MHz) 0.62 (q, 6H, J = 7.8 Hz, SiEt3), 0.63 (q, 6H, J = 7.8 Hz, SiEt3), 0.95
(t, 9H, J = 7.8 Hz, SiEt3), 0.96 (t, 9H, J = 7.8 Hz, SiEt3), 5.98 (d, 2H, J = 10.0 Hz, -CH=CH-), 6.04
(d, 2H, J = 10.0 Hz, -CH=CH-), 7.24 (d, 2H, J = 8.8 Hz, -Ar), 7.39 (d, 2H, J = 8.0 Hz, -Ar), 7.40
(d, 2H, J = 8.4 Hz, -Ar), 7.46 (d, 2H, J = 8.4 Hz, -Ar), 7.48 (d, 2H, J = 8.4 Hz, -Ar), 7.56 (d, 2H,
J = 8.3 Hz, -Ar); 13C{1H} NMR (CDCl3, 100 MHz) 6.39, 6.42, 7.04, 7.04, 71.1, 71.2, 121.2, 121.5,
126.3, 126.7, 127.7, 128.6, 131.15, 131.19, 131.7, 131.8, 138.9, 139.6, 145.1, 145.3; HRMS (ESI-
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TOF) m/z: [M + Cs]+ Calcd for C36H46Br2O2Si2Cs 857.0458, found 857.0483; IR (KBr) 726, 878,
8
9
1003, 1070, 1241, 1351, 1412, 1456, 1601, 2877, 2956.
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Synthesis of [1-[4’-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,1’-biphenyl-4-yl]-4-[4-
(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-4-triethylsilyloxycyclohexa-2,5-dien-1-
yl]oxy-triethylsilane (5fB). To a solution of 5fA (45.2 g, 62.2 mmol) in THF (600 mL) was added
BuLi (93.4 mL, 1.60 M in hexane, 0.149 mol) through a dropping funnel at -78 °C over 0.5 h.
After stirring for 1 h at this temperature, a solution of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (iPrOB(pin), 34.7 g, 0.187 mol) in THF (80 mL) was slowly added through a
dropping funnel at -78 °C, and the resulting mixture was slowly warmed to room temperature.
After stirring for 18 h at this temperature, the reaction mixture was quenched with H2O and
extracted with ethyl acetate. The combined organic layer was washed with saturated aqueous NaCl
solution, dried over Na2SO4, filtered and concentrated under reduced pressure to give a crude
mixture. Purification by silica gel chromatography (hexane/ethyl acetate = 20/1 to 9/1) afforded
5fB as a faint yellow solid in 76% yield (38.6 g).
1H NMR (CDCl3, 400 MHz) 0.59 (q, 6H, J = 7.8 Hz, SiEt3), 0.65 (q, 6H, J = 7.8 Hz, SiEt3), 0.93
(t, 9H, J = 7.8 Hz, SiEt3), 0.97 (t, 9H, J = 7.8 Hz, SiEt3), 1.35 (s, 12H, -Bpin), 1.37 (s, 12H, -Bpin),
6.01 (s, 4H, -CH=CH-), 7.41 (d, 4H, J = 8.2 Hz, -Ar), 7.53 (d, 2H, J = 8.2 Hz, -Ar), 7.61 (d, 2H, J
= 7.8 Hz, -Ar), 7.75 (d, 2H, J = 7.8 Hz, -Ar), 7.88 (d, 2H, J = 8.2 Hz, -Ar); 13C{1H} NMR (CDCl3,
100 MHz) 6.41, 6.41, 7.0, 7.1, 24.9, 71.4, 71.5, 83.7, 83.8, 125.2, 126.2, 126.4, 126.9, 131.3, 131.6,
134.7, 135.2, 139.7, 143.5, 145.4, 149.2; HRMS (ESI-TOF) m/z: [M + Cs]+ Calcd for
C48H70B2O6Si2Cs 953.3952, found 953.3975; IR (KBr) 881, 1271, 1456, 1609, 2824, 2924, 3030,
3078; mp 75.0-76.2 °C.
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Small scale synthesis of bis[μ-[[(1,1’-biphenyl)-4,4’-diyl]-1,4-bis[(triethylsilyl)oxy]-2,5-
cyclohexadiene-1,4-diyl][1,4-phenylene]]bis[(1,2,5,6-η)-1,5-cyclooctadiene]diplatinum (6f).
A suspension of 5fB (246 mg, 0.300 mmol), PtCl2(cod) (112 mg, 0.300 mmol), and K3PO4 (318
mg, 1.50 mmol) in THF (60 mL) was heated at 65 °C for 24 h. Water was added, and the resulting
mixture was extracted with CH2Cl2 (50 mL). The combined organic layer was washed with a
saturated aqueous NaCl solution, dried over Na2SO4, filtered and concentrated under reduced
pressure to give a crude mixture, which was purified by recycling preparative GPC using
chloroform as the eluent to give 6f as a colorless solid in 62% yield (162 mg). A mixture of linear
oligomers was also separated, and the amount was 51.1 mg (~20%).
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1H NMR (CDCl3, 400 MHz) 0.54 (q, 12H, J = 8.0 Hz, SiEt3), 0.60 (q, 12H, J = 8.0 Hz, SiEt3),
0.87 (t, 18H, J = 7.8 Hz, SiEt3), 0.92 (t, 18H, J = 7.8 Hz, SiEt3), 2.54 (brs, 16H, cod), 5.08 (s, 4H,
2JPt-H = 43 Hz, cod), 5.21 (s, 4H, 2JPt-H = 56 Hz, cod), 5.81 (d, 4H, J = 10 Hz, -CH=CH-), 5.98 (d,
4H, J = 10 Hz, -CH=CH-), 6.98 (d, 4H, J = 8.0 Hz, 3JPt-H = 68 Hz, -Ar), 7.07 (d, 4H, J = 8.4 Hz, -
Ar), 7.18 (d, 4H, J = 8.0 Hz, -Ar), 7.29 (d, 4H, J = 8.8 Hz, -Ar), 7.33 (d, 4H, J = 6.0 Hz, -Ar), 7.33
13
(d, 4H, J = 6.0 Hz, 3JPt-H = 64 Hz, -Ar); C{1H} NMR (CDCl3, 100 MHz) 6.45, 6.46, 7.0, 7.1,
29.8, 29.9, 71.4, 72.0, 104.2 (d, 2JPt-C = 66 Hz), 104.7 (d, 2JPt-C = 66 Hz), 125.5, 125.6, 125.7, 126.0,
1
1
126.1, 131.2 (d, JPt-C = 212 Hz), 131.5 (d, JPt-C = 212 Hz), 134.0, 135.1, 135.2, 139.7, 143.6,
154.1 (d, 1JPt-C = 229 Hz), 155.1 (d, 1JPt-C = 253 Hz); HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for
C88H116O4Si4Pt2Na 1760.7123, found 1760.7147; IR (KBr) 521, 732, 806, 1074, 1479, 1583, 1794,
2876; dp > 174 °C.
Small
scale
synthesis
of
triethyl-[[14,17,30-tris(triethylsilyloxy)-
nonacyclo[28.2.2.22,5.26,9.210,13.214,17.218,21.222,25.226,29]octatetraconta-
2,4,6,8,10,12,15,18,20,22,24,26,28,31,33,35,37,39,41,43,45,47-docosaenyl]oxy]silane (9).
A
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solution of 6f (87.1 mg, 50.0 mol) and PPh3 (65.6 mg, 250 mol) in toluene (5 mL) was heated
at 105 °C for 24 h. The resulting solution was concentrated under reduced pressure to give a crude
mixture. Purification by silica gel chromatography (hexane/CH2Cl2=4/1 to 2/1) afforded 9 as a
colorless solid in 77% yield (44 mg).
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1H NMR (CDCl3, 400 MHz) 0.64 (q, 24H, J = 7.8 Hz, SiEt3), 0.97 (t, 36H, J = 7.8 Hz, SiEt3), 6.33
(s, 8H, -CH=CH-), 6.95 (d, 8H, J = 8.8 Hz, -Ar), 7.00 (d, 8H, J = 8.4 Hz, -Ar), 7.16 (s, 8H, -Ar);
13C{1H} NMR (CDCl3, 100 MHz) 6.4, 7.0, 72.5, 126.6, 126.7, 127.7, 133.6, 139.8, 140.2, 142.4;
HRMS (MALDI-TOF) m/z: [M]+ Calcd for C72H92O4Si4 1132.6073, found 1132.6091; IR (KBr)
812, 840, 1004, 1184, 1238, 1381, 1487, 2453, 2955; mp 194-199 °C.
Large-scale synthesis of 9. A suspension of 5fB (50.0 g, 60.9 mmol), PtCl2(cod) (22.8 g, 60.9
mmol), and K3PO4 (64.7 g, 0.305 mol) in THF (4.0 L) was heated at 65 °C for 46 h. After the
resulting mixture was quenched with H2O, THF was removed under reduced pressure, and the
resulting mixture was extracted with CH2Cl2 (2.0 L  2). The combined organic layer was washed
with a saturated aqueous NaCl solution, dried over Na2SO4, filtered and concentrated under
reduced pressure to give a crude mixture, which was used for the next step without further
purification. A solution of the crude mixture and PPh3 (39.9 g, 0.152 mol) in toluene (1.25 L) was
heated at 105 °C for 24 h. The resulting solution was concentrated under reduced pressure, and
purification of the resulting crude mixture by silica gel chromatography (hexane/CH2Cl2=4/1 to
2/1) afforded 9 as a pale yellow solid in 31% yield (10.7 g, for 2 steps).
Synthesis of [8]CPP. To a solution of SnCl2ꞏ2H2O (5.08 g, 22.5 mmol) in THF (500 mL) was
added conc. HCl (3.75 mL, 12 N, 45.0 mmol) at room temperature. After stirring for 0.5 h at this
temperature, the resulting solution was added to a solution of 9 (5.80 g, 5.12 mmol) in THF (80
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mL). After stirring for 18 h at room temperature, the reaction mixture was quenched with crushed
ice and a 10% aqueous NaOH solution and extracted with CH2Cl2 (400 mL x 2). The combined
organic layer was washed with saturated aqueous NaCl solution, dried over Na2SO4, filtered and
concentrated under reduced pressure. The residue was purified by passing over a short silica gel
plug with CH2Cl2 as the eluent. The resulting solid was dispersed in MeOH, filtered, and washed
with MeOH to give [8]CPP (1.97 g, 63%) as a yellow solid. The NMR and MS spectra were
consistent with the literature data.7
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Synthesis
of
triethyl-[[14,17,30,33,46-penta[(triethylsilyl)oxy]-
tridecacyclo[44.2.2.22,5.26,9.210,13.214,17.218,21.222,25.226,29.230,33.234,37.238,41.242,45]doheptaconta2,4
,6,8,10,12,15,18,20,22,24,26,28,31,34,36,38,40,42,44,47,49,51,53,55,57,59,61,63,65,67,69,71-
tritriacontaenyl]oxy]silane (10). Ni(cod)2 (303 mg, 1.10 mmol) and 2,2’-bipyridyl (172 mg, 1.10
mmol) were dissolved in THF (50 mL), and the mixture was stirred at 50 °C for 0.5 h under a
nitrogen atmosphere. The resulting mixture was added to a solution of 5fA (363 mg, 0.500 mmol)
in THF (50 mL), and the resulting mixture was refluxed for 18 h. The reaction mixture was passed
through a pad of Celite using ethyl acetate as the eluent and was concentrated under reduced
pressure to give a crude mixture. The residue was purified by recycling preparative GPC using
chloroform as the eluent, giving 9 (59.5 mg, 21%) and 10 (96.2 mg, 34%) as off-white solids.
10: 1H NMR (CDCl3, 400 MHz) 0.65 (q, 36H, J = 8.0 Hz, -SiEt3), 0.97 (t, 54H, J = 8.0 Hz, -SiEt3),
6.05 (s, 12H, -CH=CH-), 7.47 (d, 12H, J = 8.4 Hz, -Ar), 7.58 (d, 12H, J = 8.8 Hz, -Ar), 7.67 (s,
13
12H, -Ar); C{1H} NMR (CDCl3, 100 MHz) 6.5, 7.1, 71.5, 126.4, 126.7, 127.3, 131.5, 139.4,
139.6, 145.3 ppm; HRMS (MALDI-TOF) m/z: [M + Ag]+ Calcd for C108H138O6Si6Ag 1806.8193,
found 1806.8172; IR (KBr) 748, 864, 959, 1179, 1238, 1389, 1458, 1487, 2875, 2953, 3032; dp >
272 °C.
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Synthesis of [12]CPP. To a solution of SnCl2ꞏ2H2O (43.8 mg, 194 mol) in THF (5 mL) was
added conc. HCl (32.3 L, 12 N, 388 mol) at room temperature. After stirring for 0.5 h at this
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temperature, the resulting solution was added to a suspension of 10 (50 mg, 29.4 mol) in THF
(10 mL). After stirring for 18 h at room temperature, the reaction mixture was quenched with
crushed ice and a 10% aqueous NaOH solution and extracted with CH2Cl2 (400 mL x 2). The
combined organic layer was washed with a saturated aqueous NaCl solution, dried over Na2SO4,
filtered and concentrated under reduced pressure. The residue was purified by passing over a short
silica gel plug with CH2Cl2 as the eluent. The resulting solid was dispersed in MeOH, filtered, and
washed with MeOH to give [12]CPP (15.3 mg, 57%) as a light yellow solid. The NMR and MS
spectra were consistent with the literature data.5
Synthesis
of
[1-(7-bromo-9,9-dibutyl-9H-fluoren-2-yl)-4-(4-bromophenyl)-4-
triethylsilyloxycyclohexa-2,5-dien-1-yl]oxy-triethylsilane (12A). A solution of 7 (798 mg, 3.00
mmol) in 5 mL of THF was added slowly to a slurry of sodium hydride (156 mg, 3.90 mmol, 60%
in mineral oil) in 5 mL of THF over 0.5 h at -78 °C through a cannula, and the resulting mixture
was stirred for 1 h at the same temperature. In a separate flask, BuLi (4.20 mL, 1.56 M in hexane,
6.60 mmol) was added slowly to a solution of 13 (2.61 g, 6.00 mmol) in THF (15 mL) at -78 °C
using a syringe. After stirring for 1 h at the same temperature, the resulting 2-bromo-9,9-dibutyl-
7-lithio-9H-fluorene was added through a cannula to the above-prepared solution containing 7 at
-78 °C. After stirring for 2 h at the same temperature, DMF (1.00 mL) and TES chloride (1.50 mL,
9.00 mmol) were added to the solution at approximately -50 °C. After stirring overnight at room
temperature, the reaction mixture was quenched with crushed ice and a saturated aqueous NaHCO3
solution and extracted with ethyl acetate. The combined organic layer was washed with a saturated
aqueous NaCl solution, dried over Na2SO4, filtered and concentrated under reduced pressure to
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give a crude mixture. Purification by silica gel chromatography (hexane/ethyl acetate = 100/0 to
8
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95/5) afforded 12A as a colorless solid in 64% yield (1.64 g).
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1H NMR (CDCl3, 400 MHz) 0.48-0.63 (m, 10H, Bu), 0.66 (q, 6H, J = 7.8 Hz, SiEt3), 0.68 (q, 6H,
J = 7.8 Hz, SiEt3), 0.91 (t, 9H, J = 8.0 Hz, SiEt3), 0.96 (t, 9H, J = 8.0 Hz, SiEt3), 1.08 (quin, 4H, J
= 7.6 Hz, Bu), 1.79-1.99 (m, 4H, Bu), 5.93 (d, 2H, J = 10.4 Hz, -CH=CH-), 6.10 (d, 2H, J = 10.0
Hz, -CH=CH-), 7.21 (d, 2H, J = 8.4 Hz, -Ar), 7.31 (dd, 1H, J = 8.0, 1.6 Hz, -Ar), 7.35 (dd, 1H, J
= 8.0, 1.6 Hz, -Ar), 7.35 (d, 2H, J = 8.8 Hz, -Ar), 7.42-7.47 (m, 2H, -Ar), 7.53 (d, 1H, J = 8.8 Hz,
-Ar), 7.57 (d, 1H, J = 8.4 Hz, -Ar); 13C{1H} NMR (CDCl3, 100 MHz) 6.4, 6.5, 6.99, 7.00, 13.8,
23.0, 25.9, 40.0, 55.3, 71.1, 71.3, 119.5, 120.1, 120.9, 121.0, 125.0, 126.1, 127.5, 129.9, 131.1,
131.7, 139.3, 139.7, 145.3, 145.6, 150.5, 153.1; HRMS (ESI-TOF) m/z: [M + Cs]+ Calcd for
C45H62Br2O2Si2Cs 983.1689, found 983.1703; IR (KBr) 734, 739, 968, 1009, 1067, 1107, 1240,
1402, 1456, 2874, 2955; mp 68.3-69.4 °C.
Synthesis of [1-[7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dibutyl-9H-fluoren-2-
yl]-4-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-4-triethylsilyloxycyclohexa-
2,5-dien-1-yl]oxy-triethylsilane (12B). To a solution of 12A (851 mg, 1.00 mmol) in THF (2 mL)
was added BuLi (1.50 mL, 1.58 M in hexane, 2.40 mmol) using a syringe at -78 °C over 0.5 h.
After stirring for 1 h at this temperature, a solution of i-PrOB(pin) (620 L, 3.00 mmol) was slowly
added using a syringe at -78 °C, and the resulting mixture was slowly warmed to room temperature.
After stirring for 6 h at this temperature, the reaction mixture was quenched with H2O and extracted
with ethyl acetate. The combined organic layer was washed with saturated aqueous NaCl solution,
dried over Na2SO4, filtered and concentrated under reduced pressure to give a crude mixture. The
crude mixture was washed with cold MeOH to give 12B (821 mg, 87%) as a colorless solid.
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1H NMR (CDCl3, 400 MHz) 0.57 (q, 6H, J = 8.0 Hz, SiEt3), 0.64 (q, 6H, J = 7.8 Hz, SiEt3), 0.64
(t, 6H, J = 7.6 Hz, Bu), 0.92 (t, 9H, J = 8.0 Hz, SiEt3), 0.95 (t, 9H, J = 8.0 Hz, SiEt3), 0.98 (quin,
4H, J = 7.2 Hz, Bu), 1.06 (quin, 4H, J = 7.6 Hz, Bu), 1.32 (s, 12H, -Bpin), 1.39 (s, 12H, -Bpin),
1.80-2.05 (m, 4H, Bu), 5.97 (d, 2H, J = 10.0 Hz, -CH=CH-), 6.07 (d, 2H, J = 10.0 Hz, -CH=CH-),
7.30 (d, 1H, J = 9.2 Hz, -Ar), 7.37 (d, 2H, J = 8.0 Hz, -Ar), 7.41 (s, 1H, -Ar), 7.60 (d, 1H, J = 8.0
Hz, -Ar), 7.67 (d, 1H, J = 8.0 Hz, -Ar), 7.71 (d, 2H, J = 8.4 Hz, -Ar), 7.72 (s, 1H, -Ar), 7.79 (d,
1H, J = 7.2 Hz, -Ar); 13C{1H} NMR (CDCl3, 100 MHz) 6.4, 6.5, 7.0, 7.0, 13.8, 23.0, 24.8, 24.9,
25.9, 40.0, 55.1, 71.52, 71.53, 83.6, 83.7, 119.0, 119.7, 120.3, 124.7, 125.1, 128.1, 128.8, 131.3,
131.6, 133.7, 134.7, 140.1, 143.9, 145.8, 149.2, 150.2, 151.4; HRMS (MALDI-TOF) m/z: [M +
Cs]+ Calcd for C57H86B2O6Si2Cs 1077.5204, found 1077.5218; IR (KBr) 731, 862, 962, 1007, 1080,
1146, 1360, 1611, 2934, 2957; mp 78.2-79.8 °C.
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Synthesis
of
bis[μ-[[9,9-dibutyl-9H-fluorene-2,7-diyl]-1,4-bis[(triethylsilyl)oxy]-2,5-
cyclohexadiene-1,4-diyl][1,4-phenylene]]bis[(1,2,5,6-η)-1,5-cyclooctadiene]diplatinum (14).
A suspension of 12B (212 mg, 0.400 mmol), PtCl2(cod) (150 mg, 0.400 mmol), and K3PO4 (424
mg, 2.00 mmol) in THF (80 mL) was heated at 65 °C for 24 h. Water was added, and the resulting
mixture was extracted with ethyl acetate (50 mL). The combined organic layer was washed with a
saturated aqueous NaCl solution, dried over Na2SO4, filtered and concentrated under reduced
pressure to give a crude mixture, which was purified by recycling preparative GPC using
chloroform as the eluent to give 14 as a colorless solid in 71% yield (282 mg). The ratio of two
isomers (syn-14/anti-14) was determined to be 50:50 as judged by a comparison of the integrals
of protons at cyclohexadiene-diyl moieties ( = 5.72, 5.82, 5.95, and 6.00 ppm) in the 1H NMR
analysis. A mixture of linear oligomers was also separated in ca. 15% (59.6 mg).
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1H NMR (CDCl3, 400 MHz) 0.43 (t, 12H, J = 7.6 Hz, Bu), 0.45 (t, 12H, J = 7.6 Hz, Bu), 0.55 (q,
24H, J = 8.0 Hz, SiEt3), 0.64 (q, 24H, J = 8.0 Hz, SiEt3), 0.83 (t, 36H, J = 8.0 Hz, SiEt3), 0.92 (t,
36H, J = 8.0 Hz, SiEt3), 0.85-0.99 (m, 32H, J = 8.0 Hz, SiEt3), 1.55-2.02 (m, 16H, Bu), 2.31-2.80
(m, 32H, cod), 4.85 (brs, 4H, cod), 5.17 (brs, 4H, 2JPt-H = 42 Hz, cod), 5.28 (brs, 4H, cod), 5.37
(brs, 4H, cod), 5.72 (d, 4H, J = 9.2 Hz, -CH=CH-), 5.82 (d, 4H, J = 10 Hz, -CH=CH-), 5.95 (d,
4H, J = 10 Hz, -CH=CH-), 6.00 (d, 4H, J = 10 Hz, -CH=CH-), 6.78 (d, 4H, J = 8.0 Hz, -Ar), 7.00
(d, 8H, J = 8.0 Hz, -Ar), 7.02 (d, 4H, J = 8.0 Hz, -Ar), 7.10 (d, 4H, J = 8.0 Hz, -Ar), 7.17 (dd, 4H,
J = 7.6, 3.6 Hz, -Ar), 7.21 (s, 4H, -Ar), 7.26-7.32 (m, 8H, -Ar), 7.34 (d, 4H, J = 7.6 Hz, -Ar), 7.43
(d, 4H, J = 8.0 Hz, -Ar); 13C{1H} NMR (CDCl3, 100 MHz) 6.4, 6.5, 6.6, 7.0, 7.08, 7.11, 13.9, 22.9,
23.0, 26.0, 29.75, 29.78, 39.8, 40.1, 54.5, 54.6, 70.9, 71.2, 71.5, 72.0, 103.7, 104.0, 104.4, 104.6,
118.0, 118.1, 118.3, 118.5, 119.6, 120.4, 124.2, 124.5, 124.7, 124.8, 125.0, 129.7, 130.1, 130.5,
130.8, 131.1, 131.5, 132.0, 132.1, 132.3, 132.5, 133.5, 134.9, 135.9, 136.1, 139.7, 140.8, 141.3,
143.9, 144.0, 149.7, 149.8, 149.9, 150.2, 153.2, 153.6, 155.6, 156.6; (ESI-TOF) m/z: [M + Na]+
Calcd for C106H148O4Si4Pt2Na 2009.9660, found 2009.9642; IR (KBr) 735, 812, 866, 962, 1005,
1070, 1238, 1456, 2873, 2953; dp > 186 °C.
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Synthesis of fluorene-embedded cyclic dimer (15). A solution of 14 (87.1 mg, 100 mol) and
PPh3 (131 mg, 500 mol) in toluene (10 mL) was heated at 105 °C for 18 h. The resulting solution
was concentrated under reduced pressure to give a crude mixture. Purification by silica gel
chromatography (hexane/CH2Cl2=9/1 to 4/1) afforded 15 as a colorless solid in 72% yield (99.5
mg). The ratio of two isomers was determined to be 58:42 as judged by a comparison of the
integrals of protons at cyclohexadiene-diyl moieties ( = 5.78, 5.88-6.16, and 6.38 ppm) in the 1H
NMR analysis.
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Isomer 1:1H NMR (CDCl3, 400 MHz) 0.38 (t, 6H, J = 6.4 Hz, Bu), 0.58 (q, 12H, J = 8.0 Hz, SiEt3),
0.67 (q, 12H, J = 8.0 Hz, SiEt3), 0.88 (t, 18H, J = 8.0 Hz, SiEt3), 0.97 (t, 18H, J = 8.0 Hz, SiEt3),
0.76-1.06 (m, 16H, Bu), 1.33-2.01 (m, 8H, Bu), 5.88-6.16 (m, 8H, -CH=CH-), 6.82 (d, 4H, J = 8.0
Hz, -Ar), 6.91-7.08 (m, 10H), 7.53-7.62 (m, 6H, -Ar), Isomer 2:1H NMR (CDCl3, 400 MHz) 0.38
(t, 6H, J = 6.4 Hz, Bu), 0.52 (q, 12H, J = 8.0 Hz, SiEt3), 0.66 (q, 12H, J = 8.0 Hz, SiEt3), 0.61-0.68
(m, 6H, Bu), 0.88 (t, 18H, J = 8.0 Hz, SiEt3), 0.97 (t, 18H, J = 8.0 Hz, SiEt3), 0.76-1.06 (m, 16H,
Bu), 1.33-2.01 (m, 8H, Bu), 5.78 (d, 4H, J = 10 Hz, -CH=CH-), 6.38 (d, 4H, J = 10 Hz, -CH=CH-),
6.87 (d, 4H, J = 8.0 Hz, -Ar), 6.96 (s, 2H), 6.97 (d, 8H, J = 8.0 Hz, -Ar), 7.66 (d, 4H, J = 8.4 Hz,
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-Ar), 7.70 (s, 2H, -Ar); C{1H} NMR (CDCl3, 100 MHz) 6.40, 6.44, 6.5, 6.90, 6.94, 7.1, 13.1,
13.2, 13.8, 13.9, 22.7, 23.1, 25.9, 26.3, 38.5, 40.1, 53.6, 54.8, 69.8, 71.3, 71.4, 72.5, 119.4, 120.3,
120.4, 121.3, 121.7, 122.2, 124.0, 125.7, 125.8, 126.2, 126.3, 126.5, 126.7, 126.8, 128.5, 129.6,
131.3, 131.5, 135.1, 138.5, 138.7, 138.9, 139.0, 139.3, 139.6, 140.6, 141.4, 142.8, 143.3, 143.8,
144.57, 144.64, 145.2, 151.3, 151.65, 151.73, 153.1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for
C90H124O4Si4Na 1403.8474, found 1403.8489; IR (KBr) 743, 818, 972, 1005, 1078, 1238, 1414,
1460, 2911, 2954; mp 126-129 °C.
Fluorene-embedded [8]CPP (11). To a solution of SnCl2ꞏ2H2O (29.8 mg, 132 mol) in THF (1
mL) was added conc. HCl (22 L, 12 N, 264 mol) at room temperature. After stirring for 0.5 h
at this temperature, the resulting solution was added to a solution of 15 (41.5 mg, 30 mol) in THF
(3 mL). After stirring for 6 h at room temperature, the reaction mixture was quenched with water
and a 10% aqueous NaOH solution and extracted with CH2Cl2 (5 mL x 2). The combined organic
layer was washed with saturated aqueous NaCl solution, dried over Na2SO4, filtered and
concentrated under reduced pressure. The residue was purified by passing over a short silica gel
plug with CH2Cl2 as the eluent. The resulting solid was dispersed in MeOH, filtered, and washed
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with MeOH to give 11 (20.8 mg, 81%) as a yellow solid. The ratio of two isomers (syn-11/anti-
11) was determined to be 61:39 as judged by a comparison of the integrals of protons at the 1 and
8 positions of fluorene units (syn-11:  = 6.85 ppm, anti-11: = 6.64 and 6.89 ppm) in the 1H
NMR analysis.
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1H NMR (CDCl3, 400 MHz) -0.91 ~ -0.75 (m, 6H, Bu), -0.69 (t, 3H, J = 7.6 Hz, Bu), -0.68 (t, 3H,
J = 7.2 Hz, Bu), -0.16-0.13 (m, 12H, Bu), 0.74-0.85 (m, 16H, Bu), 1.11-1.32 (m, 16H, Bu), 1.59-
1.81 (m, 16H, Bu), 6.64 (s, 2H, -Ar of anti-15), 6.85 (d, 4H, J = 1.6 Hz, -Ar of syn-15), 6.89 (d,
2H, J = 1.6 Hz, -Ar of syn-15), 7.18 (d, 1H, J = 2.0 Hz, -Ar of anti-15), 7.28-7.51 (m, 28H, -Ar),
7.52 (s, 2H, -Ar of anti-15), 7.54 (s, 8H, -Ar of syn-15), 7.55-7.57 (m, 5H, -Ar), 7.58 (d, 2H, J =
1.2 Hz, -Ar of anti-15), 7.59 (d, 2H, J = 1.6 Hz, -Ar of anti-15), 7.61 (d, 1H, J = 1.6 Hz -Ar of
anti-15); 13C{1H} NMR (CDCl3, 100 MHz) 12.1, 12.5, 13.96, 13.96, 21.4, 21.9, 23.17, 23.17,
23.76, 23.79, 27.39, 27.41, 35.0, 35.1, 42.2, 42.5, 56.7, 121.88, 121.96, 122.03, 123.3, 123.7, 126.7,
127.2, 127.4, 127.6, 128.0, 128.1, 128.2, 128.7, 129.2, 136.4, 137.1, 137.2, 137.3, 137.7, 137.9,
138.1, 138.5, 138.9, 139.7, 139.9, 140.0, 140.2, 140.8, 152.5, 152.9; HRMS (MALDI-TOF) m/z:
[M]+ Calcd for C66H64 856.5008, found 856.5021.
ASSOCIATED CONTENT
Supporting Information.
The Supporting Information is available free of charge on the ACS Publications website at DOI:
XXXXXXXXXXXXXXXX.
Synthetic and computational data (PDF)
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AUTHOR INFORMATION
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Corresponding Authors
*kayahara@scl.kyoto-u.ac.jp
* yamago@scl.kyoto-u.ac.jp
ORCID
Eiichi Kayahara: 0000-0003-1663-5273
Shigeru Yamago: 0000-0002-4112-7249
ACKNOWLEDGMENT
This work was partly supported by the Japan Society for the Promotion of Science (JSPS)
KAKENHI Grant No. 18H01962 (E.K.) and No. 16H06352 (S.Y.) and Tokyo Chemical Industry
Co. The computational studies were supported by the Super Computer Laboratory, Institute for
Chemical Research, Kyoto University.
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