Translation of helical chirality from polymer into monomer: supramolecular polymerization of a chirality-memory molecule with an asymmetric Pd(II) complex

Article abstract of DOI:10.1016/j.tet.2008.05.126

A chirality-memorizing saddle-shaped porphyrin (1_2H) with 3,5-dipyridylphenyl side arms at the opposite meso positions underwent supramolecular polymerization in CH₂Cl₂ with a chiral Pd(II) complex of 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (Pd^II(BINAP)), forming a ladder-shaped polymer (3_2H) with a prevailing one-handed helical chirality. When this polymer was poured into AcOH containing 1,3-bis(diphenylphosphino)propane (DPPP) as a decomplexing agent, 3_2H was depolymerized in a stereochemically retentive way to give optically active 1_2H, hydrogen-bonded with AcOH. Although a cyclodimeric reference of 3_2H, formed from 2_2H having two 3-pyridylphenyl meso substituents in conjunction with Pd^II(BINAP), behaved similar to 3_2H, the translation efficiency of helical chirality was lower than that in the case with 3_2H.

Full text of DOI:10.1016/j.tet.2008.05.126

Tetrahedron 64 (2008) 8264–8270
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Translation of helical chirality from polymer into monomer:
supramolecular polymerization of a chirality-memory
molecule with an asymmetric Pd(II) complex
,
,
*
Md. Akhtarul Alam a, Akihiko Tsuda a c, Yoshihisa Sei b, Kentaro Yamaguchi b, Takuzo Aida a
a Department of Chemistry and Biotechnology, School of Engineering and Center for NanoBio Integration, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
b Laboratory of Analytical Chemistry, Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences at Kagawa Campus,
Tokushima Bunri University, Shido, Sanuki-city 769-2193, Japan
c PRESTO, Japan Science Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 April 2008
Received in revised form 17 May 2008
Accepted 30 May 2008
Available online 5 June 2008
A chirality-memorizing saddle-shaped porphyrin (12H) with 3,5-dipyridylphenyl side arms at the op-
posite meso positions underwent supramolecular polymerization in CH2Cl2 with a chiral Pd(II) complex
of 2,20-bis(diphenylphosphino)-1,10-binaphthyl (PdII(BINAP)), forming a ladder-shaped polymer (32H
)
with a prevailing one-handed helical chirality. When this polymer was poured into AcOH containing
1,3-bis(diphenylphosphino)propane (DPPP) as a decomplexing agent, 32H was depolymerized in a stereo-
chemicallyretentivewaytogiveopticallyactive 12H, hydrogen-bonded with AcOH. Although a cyclodimeric
reference of 32H, formed from 22H having two 3-pyridylphenyl meso substituents in conjunction with
PdII(BINAP), behaved similar to 32H, the translation efficiency of helical chirality was lower than that in the
Keywords:
Porphyrin
Helical polymer
Supramolecular polymerization
Depolymerization
Chiral memory
case with 32H
.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
because of a rapid saddle-to-saddle macrocyclic inversion. In 1997,
we reported that such a thermodynamic equilibrium can be shifted
to either of the two enantiomeric forms of SP by a 1:2 hydrogen-
bonding interaction with chiral acids such as mandelic acid (MA)
(Chart 1).4a Furthermore, the induced enantiomeric bias can be
fixed by pouring this hydrogen-bonded complex into achiral acids
such as acetic acid (AcOH) (Scheme 1). In this system, the hydro-
gen-bonded MA molecules are kicked out from SP by AcOH, but the
inversion of the porphyrin macrocycle, leading to racemization of
SP, can be suppressed by regenerated hydrogen bonds with AcOH.
Because of this unique feature, we named SP as a chirality-memory
molecule. After this work, some other molecular and supramolec-
ular systems such as poly(phenyl acetylene) derivatives6 and as-
sembled calixarenes7 have been found to possess an analogous
chiroptical feature that may be referred to as ‘chirality memory’.4
In our previous study,8 we demonstrated that compound 102H
having 3,5-dipyridylphenyl side arms at the opposite meso posi-
tions (Chart 1) undergoes supramolecular polymerization by
coordination with a Pt(II) complex of 1,3-bis(diphenylphosphino)-
propane (DPPP), forming a ladder-shaped polymer.9,10 Of interest,
we found that interaction of 102H in the ladder polymer with MA
forms a prevailing one-handed helical chirality along the main
chain. This is due to conformational interlocking of the meso-aryl
groups with the porphyrin macrocycle. Namely, if the two meso-
Helical polymers are an attractive chiral motif in a variety of
aspects. Since the discovery of synthetic helical polymers,1 their
chemistry has been studied extensively.2 One of the attractive
subjects in relation to supramolecular chemistry is the chiroptical
sensing of asymmetric small molecules by helical polymers, where
the guest chirality is translated into a prevailing one-handed helical
chirality of the hosting polymers.3
In the present study, we explored an interesting possibility that
such a one-handed or enantiomerically biased helical chirality
might be translated from polymers into the constituting mono-
mers. In order to realize this concept, we paid attention to a certain
family of saddle-shaped porphyrins (SP) with a symmetry group
D2.4 Because of the steric repulsion among the neighboring meso
and pyrrole-b substituents on the periphery, SP adopts a nonplanar,
saddle-shaped conformation.5 Due to this nonplanar structure
along with the presence of two different substituents (Scheme 1,
green and blue) at the neighboring meso positions, SP is chiral.
However, the enantiomers of SP are not separable from one another
* Corresponding author. Tel.: þ81 3 5841 7251; fax: þ81 3 5841 7310.
E-mail address: aida@macro.t.u-tokyo.ac.jp (T. Aida).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.05.126

Md.A. Alam et al. / Tetrahedron 64 (2008) 8264–8270
8265
aryl groups are twisted in a clockwise or counterclockwise di-
rection relative to one another, the nonplanar porphyrin macro-
cycle is inverted from one enantiomeric form to the other through
a planar transition structure. This interlocked conformation gave us
a new idea that use of a chiral metal complex as the linker for the
ladder polymer (32H) might give rise to a helical twist of the main
chain, and this helical twisting might bias the chirality of the por-
phyrin macrocycle to either of the two enantiomeric forms. If this
mechanism indeed operates, one should obtain 102H, hydrogen-
bonded with AcOH, in an optically active form by stereochemically
retentive depolymerization of 32H in AcOH containing DPPP as
a decomplexing agent. As reported in the present paper, we suc-
ceeded in translating the helical chirality of supramolecular poly-
mer 32H into the monomer porphyrin (Scheme 2). Here we used
1
2H, an advanced version of 102H in terms of its enhanced solubility,
in combination with a chiral Pd(II) complex of BINAP (PdII(BINAP))
for supramolecular polymerization. For comparison, we utilized
compound 22H, which was intended to form a cyclic dimer by co-
ordination with PdII(BINAP).
2. Results and discussion
Saddle-shaped porphyrin 12H was newly synthesized by a pro-
cedure analogous to that reported previously,8 and unambiguously
characterized by means of 1H NMR, absorption, and IR spectros-
copies, along with MALDI-TOF mass spectrometry (see Section 4).
The self-assembling behavior of 12H via coordination with chiral
metal complex PdII(BINAP) was investigated by electronic absorp-
tion, circular dichroism (CD), and 1H/31P/19F NMR spectroscopy,
together with dynamic light-scattering analysis. When 1H2 was ti-
trated with PdII(BINAP) in CH2Cl2, the Soret and Q bands at 473 and
686 nm, respectively (Fig. 1, purple curve), were intensified at the
expense of the original absorbances of 1H2 at 446 and 540 nm
(Fig. 1, black curve). These absorption spectral changes reached
a plateau when 2 equiv of PdII(BINAP) with respect to 1H2 were
added to the solution (Fig. 1, inset). Dynamic light-scattering (DLS)
analysis of a 1:2 mixture of 12H and PdII(BINAP) indicated the
Scheme 1. Schematic representations of (1) chirality transfer from mandelic acid (MA)
to D2-symmetric saddle-shaped porphyrin (SP) through hydrogen-bonding in-
teractions (SP$MA2) and (2) memorization of the resulting configurations in acetic acid
(AcOH) in the form of SP$(AcOH)2.
a
Chart 1.

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Md.A. Alam et al. / Tetrahedron 64 (2008) 8264–8270
Scheme 2. Schematic representations of (1) induction of a helical chirality by supramolecular polymerization of chirality-memorizing 12H with chiral PdII(BINAP) and (2) its
translation into the chirality of monomer 12H (hydrogen-bonded with AcOH) by stereochemically retentive depolymerization in AcOH containing 1,3-bis(diphenylphosphino)-
propane (DPPP) as a decomplexing agent.

Md.A. Alam et al. / Tetrahedron 64 (2008) 8264–8270
8267
displayed upfield-shifted signals most likely due to their mutual
magnetic shielding. The selective cyclodimerization of 2Ni with
PdII(BINAP),8 thus observed, may support our hypothesis that 12H
possibly forms polymer 32H with bridging PdII(BINAP) units
(Scheme 2).
A 1:2 mixture of 12H and (R)-PdII(BINAP) in CH2Cl2 (polymer 32H
)
displayed a distinct circular dichroism (CD) spectral feature at the
absorption bands due to the binaphthyl ligands (300–400 nm) and
saddle-shaped porphyrin moieties (400–550 nm) (Fig. 3, pink solid
curve). When the (S)-isomer of PdII(BINAP) was allowed to co-
ordinate with 12H, the observed CD spectral feature was a mirror
image (Fig. 3, blue solid curve) of the above. Figure 4 shows plots of
the CD intensities of 12H at 485 nm upon complexation with
PdII(BINAP) of different enantiomeric excess (ee) values. A linear
correlation indicates that the chiroptical feature of the resulting
polymer is given by the added chiral PdII(BINAP).14 As a control
Figure 1. Electronic absorption spectra of 12H (5.0ꢂ10ꢀ6 M) in CH2Cl2 at 20 ꢁC upon
titration with PdII(BINAP) (15.0ꢂ10ꢀ6 M). Inset shows plots of the absorbances of 12H at
473 nm at different ratios of [PdII(BINAP)]/[12H].
presence of light-scattering particles with dimensions ranging from
100 to 500 nm (average diameter¼350 nm, Fig. 2). Because of this
association, 1H NMR signals of 12H in CD2Cl2 were very broad.
Similar broadening was observed for the 31P NMR signal at 25 ppm
and 19F NMR signal at ꢀ79 ppm, due to BINAP and CF3SOꢀ3 ,
respectively, suggesting that both the triflate anion and the PdII-
(BINAP) cation are included in the assembly.11 For structural elu-
cidation of polymeric assembly 32H, we synthesized 22H, a reference
saddle-shaped porphyrin bearing only one pyridyl group in each
meso-aryl group (Chart 1), with an expectation that 22H could form
a metal-bridged cyclic dimer8 in a manner analogous to that
expected for the supramolecular polymerization of 12H (Scheme 2).
To avoid analytical complexity due to protonation of 22H, its nickel
complex 2Ni was allowed to coordinate with PdII(BINAP) in CH2Cl2.
Similar to the case with PtII(DPPP) reported previously,8 cold-spray
Figure 3. CD spectra in CH2Cl2 at 20 ꢁC of mixtures 12H/(R)-PdII(BINAP) (pink solid
curve) and 12H/(S)-PdII(BINAP) (blue solid curve), together with 22H/(R)-PdII(BINAP)
12
ionization mass spectrometry (CSI-MS) of their equimolar mix-
(pink
broken
curve)
and
2
2H/(S)-PdII(BINAP)
(blue
broken
curve).
ture displayed intense peaks at m/z¼1937,1241, and 893, assignable
to the 2:2 complex losing two, three, and four CF3SOꢀ3 counter
anions, respectively, at the ionization step.11 No peaks assignable to
higher oligomers were detected. In CD2Cl2 at 20 ꢁC, the 1:1 mixture
[12H]¼[22H]¼5.0ꢂ10ꢀ6 M. [PdII(BINAP)]¼11.7ꢂ10ꢀ6 M for 12H and 5ꢂ10ꢀ6 M for 22H
.
showed a sharp singlet 31P NMR signal at
d
25.03 ppm11 (cf.
36.43 ppm for PdII(BINAP)) due to pyridine-coordinated PdII-
(BINAP), along with a sharp singlet 19F NMR signal at
d
ꢀ78.8 ppm11
due to non-coordinated CF3SOꢀ3 .13 Because of this coordinative in-
teraction, the pyridyl groups of 2Ni in the cyclodimeric assembly
showed downfield-shifted 1H NMR signals from those of mono-
11
meric 2Ni
.
In contrast, other peripheral groups of assembled 2Ni
Figure 4. Plots of CD intensities at 485 nm of self-assembled 12H/PdII(BINAP) in CH2Cl2
observed at different enantiomeric excess (ee) values of PdII(BINAP). [12H]¼5ꢂ10ꢀ6 M.
[PdII(BINAP)]¼11.7ꢂ10ꢀ6 M.
Figure 2. Histogram profile in dynamic light scattering (DLS) in CH2Cl2 at 20 ꢁC of
a 1:2 mixture of 12H (1.5ꢂ10ꢀ3 M) and PdII(BINAP) (3.0ꢂ10ꢀ3 M).

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Md.A. Alam et al. / Tetrahedron 64 (2008) 8264–8270
experiment, we added (R)- or (S)-PdII(BINAP) to a reference saddle-
shaped porphyrin without any pyridyl side arms. However, no CD
signal emerged at the Soret absorption band of the porphyrin,
indicating that the observed CD for 12H upon mixing with (R)- or
(S)-PdII(BINAP) is the consequence of the complexation of its
dipyridylphenyl side arms, rather than its nitrogen core, with PdII-
(BINAP). We assume that supramolecular polymer 32H, formed
from 12H and PdII(BINAP), may adopt a helical structure, where the
dipyridylphenyl side arms in each porphyrin unit are twisted rel-
ative to one another in either clockwise or counterclockwise di-
rection, and the helical sense is determined by the absolute
configuration of bridging chiral PdII(BINAP). This structural feature
could result in a twisted array of the porphyrin units, thereby
exerting an efficient exciton coupling between the neighboring
porphyrin units. While the cyclic dimer of 22H, bridged by (R)- or
(S)-PdII(BINAP) ([PdII]/[22H]¼1.25), displayed a CD spectral feature
(Fig. 3, pink and blue broken curves, respectively) similar to its
polymeric version, the CD intensity at the Soret absorption band
(475–520 nm) was obviously smaller (Fig. 3). Thus, the cyclic dimer,
as expected, may possess a greater geometrical freedom than its
polymeric version.
Figure 6. CD spectra in DPPP-containing AcOH (DPPP/Pd¼5) at 20 ꢁC of mixtures 12H
/
(R)-MA (pink solid curve), 12H/(S)-MA (blue solid curve), 12H/(R)-PdII(BINAP) (pink
broken curve), and 12H/(S)-PdII(BINAP) (blue broken curve) after immersion for 60 min.
[12H]¼5ꢂ10ꢀ6 M, [MA]¼11.0ꢂ10ꢀ6 M, and [PdII(BINAP)]¼11.7ꢂ10ꢀ6 M.
As described in the introductory part, the possibility of trans-
lating the helical chirality of 32H into 12H (Scheme 2) was in-
vestigated by taking advantage of the chirality-memorizing ability
of 12H (vide ante) hydrogen-bonded with acids (Scheme 1).4 Thus,
supramolecular polymer 32H was poured into DPPP-containing
AcOH ([DPPP]/[Pd(II)]¼5), with an expectation that it may disso-
ciate into the protonated form of the monomer with retention of its
configuration (Scheme 2).8 As shown in Figure 5 (solid curves), the
intensity of the CD spectrum decreased entirely, most likely due to
the disappearance of the exciton coupling, operating among the
assembled porphyrin units, upon dissociation into 12H$(AcOH)2.
However, the spectral change subsided immediately, where the
resultant CD spectrum remained unchanged for the next 5 h at
20 ꢁC. The CD spectral profile is virtually identical to that observed
for the hydrogen-bonded 12H, formed by pouring the binary mix-
ture of 12H and (R)-MA into DPPP-containing AcOH (Fig. 6, pink
solid curve). In fact, the formation of hydrogen-bonded 12H from
polymeric 32H was confirmed by 1H NMR spectroscopy measured
in AcOH-d4.11 Although the final CD intensity after the dissociation
of polymer 32H was just 37% as large as those observed for
AcOH-treated MA complex of 12H (Fig. 6), one can conclude that
the helical chirality of 32H gives rise to an enantiomeric bias of
its monomer component8 (Fig. 5, solid curves). As a control
experiment, we simply immersed polymer 32H in DPPP-containing
CH2Cl2 in the absence of AcOH. While 32H dissociated into 12H by
the action of DPPP, the CD spectrum lost the activity at the Soret
absorption band of 12H (450–525 nm) and simply displayed CD
bands characteristic of PdII(BINAP)(DPPP) in CH2Cl2.11 Thus, the
assay we employed here indeed takes advantage of the chirality-
memorizing ability of the hydrogen-bonded form of 12H. Mean-
while, the cyclic dimer composed of 22H and PdII(BINAP), upon
being poured into DPPP-containing AcOH, showed a CD spectral
change (Fig. 5, broken curves) similar to its polymeric version.
However, the CD intensity finally attained was only a half of that
observed for the case starting from the polymeric version. From
these results, we consider that coordinating PdII(BINAP) in the main
chain of 32H with a much smaller geometrical freedom than in the
cyclodimeric reference can give rise to a more twisted geometry of
the porphyrin array, resulting in a larger enantiomeric bias of the
chiral saddle.
3. Conclusions
A chirality-memorizing saddle-shaped porphyrin (12H) with
3,5-dipyridylphenyl side arms at the opposite meso positions un-
dergoes supramolecular polymerization with a chiral Pd(II) com-
plex of BINAP, forming a ladder-shaped polymer (32H) having
a prevailing one-handed helical chirality. By stereochemically re-
tentive depolymerization of 32H in DPPP-containing AcOH, optically
active 12H, hydrogen-bonded with AcOH, was obtained. The results
presented here indicate the successful translation of a helical chi-
rality from polymer 32H into monomer 12H. The principle of this
idea may not be limited to the system reported here but might be
extendable to general asymmetric syntheses.
4. Experimental section
4.1. General
All reagents and solvents were used as-received from com-
mercial sources without further purification. The enantiomers
of mandelic acid (MA) (>99%), 1,3-bis(diphenylphosphino)pro-
pane (DPPP), [(R)-2,20-bis(diphenylphosphino)-1,10-binaphthyl]-
palladium(II) chloride, and CF3SO3Ag were purchased from
Aldrich. The enantiomers of [PdII(BINAP)][(OTf)2],10c 5-(2,6-di-
methoxyphenyl)-2,3,7,8-tetramethylpyrromethane,4a and 2,3,7,8,
12,13,17,18-octamethyl-5,15-bis(2,6-dimethoxyphenyl)-10,20-bis[3-
Figure 5. CD spectra in DPPP-containing AcOH (DPPP/Pd¼5) at 20 ꢁC of mixtures 12H
/
(R)-PdII(BINAP) (pink solid curve) and 12H/(S)-PdII(BINAP) (blue solid curve), together
with 22H/(R)-PdII(BINAP) (pink broken curve) and 22H/(S)-PdII(BINAP) (blue broken
curve). [12H]¼[22H]¼5ꢂ10ꢀ6 M. [PdII(BINAP)]¼11.7ꢂ10ꢀ6 M for 12H and 5ꢂ10ꢀ6 M
for 22H
.

Md.A. Alam et al. / Tetrahedron 64 (2008) 8264–8270
8269
(4-pyridyl)phenyl]porphine8 were synthesized according to the
literature methods.
For column chromatography, Wakogel C-300HG (particle size
40–60 mm, silica), C-400HG (particle size 20–40 mm, silica), alu-
minum oxide 90 standardized (Merck), or Bio-BeadsÔ S-X1 (BIO
RAD) was used.
Circular dichroism (CD) and electronic absorption spectra were
recorded on a JASCO type J-820 spectropolarimeter equipped with
a JASCO type PTC-423L temperature/stirring controller and a
JASCO type V-570 UV/vis/NIR spectrometer equipped with a JASCO
type ETC-505T temperature/stirring controller, respectively. 1H,
19F, and 31P NMR spectra were recorded on a JEOL model EX-270
methyl); IR (KBr): 2924, 2853, 1699, 1599, 1547, 1438, 1405, 1380,
1339, 1230, 1185, 1120, 1070, 994, 932, 837, 775, 754, 722, 697, 614,
540, 504 cmꢀ1; FABMS m/z calcd for Mþ (C29H36N2O2) 445, found
446 (MþHþ).
4.2.3. Nickel complex of 2,3,7,8,12,13,17,18-octamethyl-5,15-bis-
(2,6-dimethoxyphenyl)-10,20-bis[3,5-bis(4-pyridyl)-4-
dodecyloxyphenyl]porphine (1Ni
)
To a propionic acid solution (300 mL) of 3,5-bis(4-pyridyl)-4-
dodecyloxybenzaldehyde (1.75 g, 3.93 mmol) was added at 0 ꢁC
a
CHCl3 solution (20 mL) of 5-(2,6-dimethoxyphenyl)-2,3,7,8-
tetramethylpyrromethane4a (1.32 g, 3.36 mmol). The mixture was
stirred for 12 h at room temperature and evaporated to dryness.
The residue was dissolved in AcOH (200 mL) containing
Ni(OAc)2$4H2O (3.34 g, 13.4 mmol) and the mixture was stirred
under reflux for 12 h. The reaction mixture was evaporated to
dryness under reduced pressure and the residue was dissolved
into CHCl3, treated with NaHCO3 for neutralization, and extracted
with CHCl3/water. The combined organic extract was washed
with brine, dried over anhydrous Na2SO4, and evaporated to
dryness. The residue was chromatographed on silica gel with
CHCl3/MeOH (100:3) as an eluent, where the reddish purple
fraction was collected. Evaporation of this fraction and re-
crystallization of the residue from CH2Cl2/hexane gave 1Ni
or GSX-500 spectrometer, where chemical shifts (d in parts per
million) were determined with respect to tetramethylsilane (TMS),
hexafluorobenzene (C6F6), and phosphoric acid (H3PO4), re-
spectively, as internal standards. Matrix-assisted laser desorption/
ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was
performed with 9-nitroanthracene as a matrix on an Applied
Biosystems BioSpectrometry WorkstationÔ model Voyager-DEÔ
STR spectrometer. Fast atom bombardment (FAB) mass spectro-
metry was performed with 3-nitrobenzylalcohol as a matrix on a
JEOL type JMS-BU30 LC MATE spectrometer. Cold-spray ionization
(CSI) mass spectrometry was performed on a JEOL model JMS-
700T spectrometer with a CSI source. Dynamic light-scattering
(DLS) measurement was performed on an Otsuka model ELS-Z2
instrument.
(161 mg, 8% yield) as purple solid. UV/vis (CH2Cl2), lmax
M
(3/
ꢀ1 cmꢀ1)¼432 (45,000), 551 (3200), and 589 (3100) nm; 1H
NMR (270 MHz, CDCl3, 20 ꢁC):
d
8.69 (8H, d, J¼5.6 Hz, PyH), 7.97
4.2. Procedures for the synthesis of saddle-shaped porphyrin
12H and its nickel complex 1Ni
(4H, s, o-H of C6H3Py2), 7.71 (8H, d, J¼5.9 Hz, PyH), 7.57 (2H, t,
J¼8.2 Hz, p-H of C6H3(OMe)2), 6.83 (4H, d, J¼8.4 Hz, m-H of
C6H3(OMe)2), 3.63 (12H, s, OCH3), 3.42 (4H, t, J¼6.2 Hz, OCH2),
4.2.1. 3,5-Dibromo-4-dodecyloxybenzaldehyde (4)
2.01 (12H, s, CH3 at pyrrole-b), 1.96 (12H, s, CH3 at pyrrole-b),
A THF/DMF (4:1) solution (100 mL) of a mixture of 3,5-dibromo-
4-hydroxybenzaldehyde (3.00 g, 10.7 mmol), 1-bromododecane
(2.70 g, 10.8 mmol), and K2CO3 (4.50 g, 32.5 mmol) was refluxed for
24 h under Ar. The reaction mixture was filtered off from an in-
soluble fraction and the filtrate was evaporated to dryness. The
residue was poured into water and extracted with CHCl3. The
combined organic extract was dried over Na2SO4 and chromato-
graphed on silica gel with CHCl3/hexane (3/7 v/v) as an eluent,
where the first fraction was collected and evaporated to give 4 as
white solid in 73% yield (3.5 g, 7.81 mmol), mp 47 ꢁC. 1H NMR
1.65–1.07 (40H, m, CH2), and 0.87 (6H, t, J¼6.7 Hz, CH3); IR (KBr):
2922, 2852, 1593, 1547, 1471, 1402, 1380, 1355, 1340, 1314, 1249,
1175, 1109, 1070, 1034, 992, 970, 899, 855, 825, 775, 730, 671, 648,
605, 545 cmꢀ1; MALDI-TOF MS m/z calcd for Mþ (C100H112N8NiO6)
1580, found 1580.
4.2.4. 2,3,7,8,12,13,17,18-Octamethyl-5,15-bis(2,6-dimeth-
oxyphenyl)-10,20-bis[3,5-bis(4-pyridyl)-4-dodecyloxyphenyl]-
porphine (12H
)
To a CHCl3 solution (30 mL) of 1Ni (97 mg, 80
mmol) was added
(270 MHz, CDCl3, 20 ꢁC):
d
9.80 (1H, s, aldehyde), 7.97 (2H, s, ArH),
35% aq HCl (10 mL) and the mixture was stirred for 12 h at room
temperature. The reaction mixture was neutralized with aq
NaHCO3 and extracted with CH2Cl2. The combined organic extract
was washed with brine, dried over anhydrous Na2SO4, and evapo-
rated to dryness. A benzene solution of the residue was freeze-
dried to give 12H (89 mg 96% yield) as brown solid. UV/vis (CH2Cl2),
4.04 (2H, t, J¼6.5 Hz, alkyl), 1.91–1.81 (2H, m, alkyl), 1.57–1.24 (18H,
m, alkyl), 0.85 (3H, t, J¼6.6 Hz, methyl); IR (KBr): 2918, 2851, 1686,
1579, 1544, 1471, 1450, 1365, 1263, 1207, 1185, 1065, 1027, 1016, 984,
945, 925, 884, 741, 716, 661, 579, 543 cmꢀ1; FABMS m/z calcd for Mþ
(C19H28Br2O2) 448, found 449 (MþHþ).
lmax
(
3
/Mꢀ1 cmꢀ1)¼456 (47,000), 542 (3600), 582 (3600), 632
1
4.2.2. 3,5-Bis(4-pyridyl)-4-dodecyloxybenzaldehyde (5)
(3800), and 688 (3200) nm; H NMR (270 MHz, CDCl3, 20 ꢁC):
A 1,4-dioxane solution (80 mL) of a mixture of 4 (2.00 g,
4.46 mmol), 4-pyridineboronic acid (2.00 g, 16.27 mmol), and
K3PO4$nH2O (5.5 g) was bubbled with Ar for 30 min. Tetrakis-
(triphenylphosphine)palladium(0) (2.50 g, 2.16 mmol) was added
to this solution and the mixture was refluxed for 3 days in an Ar
atmosphere. To this reaction mixture were successively added
CHCl3, water, and ethylene diamine (20, 20, and 0.5 mL, re-
spectively). The reaction mixture was filtered off from an insoluble
fraction and the filtrate evaporated to dryness. The residue was
poured into water and extracted with CHCl3. The combined or-
ganic extract was dried over Na2SO4 and chromatographed on
silica gel with CHCl3/MeOH (98/2 v/v) as an eluent, where the
first fraction was collected and evaporated to give 5 as white
solid in 76% yield (1.5 g, 3.37 mmol). 1H NMR (270 MHz, CDCl3,
d
8.72 (8H, d, J¼5.0 Hz, PyH), 8.22 (4H, s, o-H of C6H3Py2), 7.77 (8H,
d, J¼5.0 Hz, PyH), 7.65 (2H, t, J¼8.1 Hz, p-H of C6H3(OMe)2), 6.92
(4H, d, J¼8.1 Hz, m-H of C6H3(OMe)2), 3.66 (12H, s, OCH3), 3.46 (4H,
t, J¼6.2 Hz, OCH2), 2.05 (12H, s, CH3 at pyrrole-
b), 1.98 (12H, s, CH3
at pyrrole-
b
), 1.35–1.08 (40H, m, CH2), and 0.87 (6H, t, J¼6.7 Hz,
CH3); IR (KBr): 3367, 2923, 2852, 1595, 1546, 1470, 1445, 1404, 1382,
1318, 1250, 1229, 1159, 1131, 1109, 1070, 1033, 957, 866, 822, 775,
732, 644, 605, 545 cmꢀ1; MALDI-TOF MS m/z calcd for Mþ
(C100H114N8O6) 1524, found 1524.
Acknowledgements
The present work was sponsored by a Grants-in-Aid for
Scientific Research (No. 17350044) and Encouragement of Young
Scientists (No. 18750113) from the Ministry of Education, Science,
Sports, and Culture, Japan. M.A.A. thanks the JSPS Postdoctoral
Fellowship for Foreign Researchers.
20 ꢁC):
d
10.04 (1H, s, aldehyde), 8.71 (4H, d, J¼5.9 Hz, pyridyl),
7.93 (2H, s, ArH), 7.57 (4H, d, J¼5.9 Hz, pyridyl), 3.27 (2H, t,
J¼6.2 Hz, alkyl), 1.27–0.89 (20H, m, alkyl), 0.85 (3H, t, J¼6.7 Hz,

8270
Md.A. Alam et al. / Tetrahedron 64 (2008) 8264–8270
Alam, M. A.; Tsuda, A.; Kinbara, K.; Yamaguchi, K.; Aida, T. Angew. Chem., Int. Ed.
Supplementary data
2006, 45, 3786–3790.
5. (a) Barkigia, K. M.; Berber, M. D.; Fajer, J.; Medforth, C. J.; Renner, M. W.; Smith,
K. M. J. Am. Chem. Soc. 1990, 112, 8851–8857; (b) Barkigia, K. M.; Fajer, J.; Berber,
M. D.; Smith, K. M. Acta Crystallogr., Sect. C 1995, 51, 511–515.
6. (a) Yashima, Y.; Maeda, K.; Okamoto, Y. Nature 1999, 399, 449–451; (b) Yashima,
Y.; Maeda, K.; Nishimura, T. Chem.dEur. J. 2004, 10, 42–51.
7. (a) Prins, L. J.; Jong, F. D.; Timmerman, P.; Reinhoudt, D. N. Nature 1999, 398,
498–502; (b) Prins, L. J.; Jong, F. D.; Timmerman, P.; Reinhoudt, D. N. Nature
2000, 408, 181–184.
Synthetic schemes of saddle-shaped porphyrin 1, 1H, 31P, 19F
NMR, CSI mass, and CD spectra of complexes 12H and 2Ni with/
without PdII(BINAP) are provided. Supplementary data associated
with this article can be found in the online version, at doi:10.1016/
j.tet.2008.05.126.
8. Toyofuku, K.; Alam, M. A.; Tsuda, A.; Fujita, N.; Sakamoto, S.; Yamaguchi, K.;
Aida, T. Angew. Chem., Int. Ed. 2007, 46, 6476–6480.
9. (a) Ayabe, M.; Yamashita, K.; Sada, K.; Shinkai, S.; Ikeda, A.; Sakamoto, S.;
Yamaguchi, K. J. Org. Chem. 2003, 68, 1059–1066; (b) Ikeda, A.; Ayabe, M.;
Shinkai, S. Chem. Lett. 2001, 1138–1139.
10. (a) Fan, J.; Whiteford, J. A.; Olenyuk, B.; Levin, M. D.; Stang, P. J.; Fleischer, E. B.
J. Am. Chem. Soc. 1999, 121, 2741–2752; (b) Olenyuk, B.; Whiteford, J. A.; Stang,
P. J. J. Am. Chem. Soc. 1996, 118, 8221–8230; (c) Stang, P. J.; Olenyuk, B.; Arif,
A. M. Organometallics 1995, 14, 5281–5289; (d) Fujita, N.; Biradha, K.; Fujita, M.;
Sakamoto, S.; Yamaguchi, K. Angew. Chem., Int. Ed. 2001, 40, 1718–1721.
11. See Supplementary data.
References and notes
1. (a) Nolte, R. J. M.; Beijinen, A. J. M.; Drenth, W. J. Am. Chem. Soc. 1974, 96, 5932–
5933; (b) Yuki, H.; Kiji, H.; Okamoto, Y. J. Polym. Sci., Polym. Lett. Ed. 1977, 15,
589–593.
2. (a) Green, M. M.; Peterson, N. C.; Sato, T.; Takemoto, A.; Cook, R.; Lifson, S.
Science 1995, 268, 1860–1866; (b) Green, M. M.; Garetz, B. A.; Munoz, G. B.;
Chang, H. J. Am. Chem. Soc. 1995, 117, 4181–4182.
3. (a) Okamoto, Y.; Yashima, E. Angew. Chem., Int. Ed. 1998, 37, 1020–1043;
(b) Yashima, Y.; Maeda, Y.; Okamoto, Y. J. Am. Chem. Soc. 1998, 120, 8895–
8896.
12. Yamaguchi, K. J. Mass. Spectrom. 2003, 38, 473–490.
13. Lawrance, G. A. Chem. Rev. 1986, 86, 17–33.
4. (a) Furusho, Y.; Kimura, T.; Mizuno, Y.; Aida, T. J. Am. Chem. Soc. 1997, 119, 5267–
5268; (b) Mizuno, Y.; Aida, T.; Yamaguchi, K. J. Am. Chem. Soc. 2000, 122, 5278–
5285; (c) Mizuno, Y.; Aida, T. Chem. Commun. 2003, 20–21; (d) Mizuno, Y.;
14. (a) Spector, M. S.; Selinger, J. V.; Singh, A.; Rodriguez, J. M.; Price, R. R.; Schnur,
J. M. Langmuir 1998, 14, 3493–3500; (b) Hirst, A. R.; Huang, B.; Castelletto, V.;
Hamley, I. W.; Smith, D. K. Chem.dEur. J. 2007, 13, 2180–2188.