Various synthetic routes to a gable-like bis(porphyrin) constructed on a 1,10-phenanthroline chelate

Article abstract of DOI:10.1002/ejoc.200900149

Three different synthetic routes to obtain a gable-like bis(porphyrin) are described. The two porphyrins are covalently linked to a 2,9-diphenyl-l.,10- phenanthroline chelate. One way to gain access to the bis(porphyrin) relies on the simultaneous constru

Full text of DOI:10.1002/ejoc.200900149

FULL PAPER
DOI: 10.1002/ejoc.200900149
Various Synthetic Routes to a Gable-Like Bis(porphyrin) Constructed on a
1,10-Phenanthroline Chelate
Maryline Beyler,[a] Christine Beemelmanns,[a] Valérie Heitz,*[a] and Jean-Pierre Sauvage[a]
Keywords: Synthesis design / Porphyrinoids / Cross-coupling / Macrocycles
Three different synthetic routes to obtain a gable-like bis-
(porphyrin) are described. The two porphyrins are covalently
linked to a 2,9-diphenyl-1,10-phenanthroline chelate. One
way to gain access to the bis(porphyrin) relies on the simulta-
neous construction of two porphyrins on a 2,9-bis(para-for-
mylphenyl)-1,10-phenanthroline, whereas the other two are
based on Suzuki cross-coupling reactions between a presyn-
thesised porphyrin and an appropriate phenanthroline deriv-
ative.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
procedure to assemble a [2]catenane by using coordination
bonds only.[7] We would now like to describe the different
synthetic routes tested to obtain this potentially multipur-
pose bis(porphyrin) chelate.
Introduction
Porphyrins are key components in very diverse fields of
research because of their well-defined binding sites and
interesting chemical and photochemical properties. Their
use in the construction of sophisticated multicomponent
architectures is related to the development of simple syn-
thetic protocols to nonsymmetrical porphyrin–macrocycle
conjugates functionalised either on the meso positions or
on the pyrrolic sites of the porphyrin.[1] Oblique bis(por-
phyrin)s have been made and studied since the beginning of
the 1980s as models of various natural biological systems
related to allostery in haemoglobin or photosynthesis.[2]
The first compound of this family was made by the group
of Tabushi, and it was named “gable” porphyrin.[3] Later
on, several groups embarked on the synthesis and the study
of related gable porphyrins with various spacers between
the two tetrapyrrolic rings, in relation to biomimetic pro-
jects, as already mentioned, and to host–guest chemistry.
Our own group has been interested in electron and energy-
transfer processes from an early stage, and the first 1,10-
phenanthroline-based gable bis(porphyrin) has been at the
origin of a large body of studies related to catenanes and
rotaxanes, which were made and investigated as models of
an important fragment of the bacterial photosynthetic reac-
tion centre,[4] consisting of the special pair (primary elec-
tron donor) and bacteriopheophytin (primary electron
acceptor).[5] More recently, we have used a metallated
zinc(II) bis(porphyrin) constructed on the 1,10-phenan-
throline chelate as a receptor for dipyridylporphyrin to
build a tris(porphyrinic) macrocycle.[6] The same zinc(II)
bis(porphyrin) motif is also the key building block of a new
Results and Discussion
Three different strategies were explored to find a com-
promise between the number of synthetic steps and the
amount of final bis(porphyrin) obtained. The correspond-
ing retrosynthetic schemes are depicted in Scheme 1. They
are based on the simultaneous construction (Route A) or
attachment (Routes B and C) of two porphyrins on an ap-
propriate functionalised 1,10-phenanthroline.
Route A (Scheme 1) relies on a double porphyrin-form-
ing reaction carried out on 2,9-bis(4-formylphenyl)-1,10-
phenanthroline (2) from pyrrole and 3,5-di-tert-butylbenz-
aldehyde. The two other routes are modular: Route B is
based on a double Suzuki coupling reaction between 2,9-
bis(4-bromophenyl)-1,10-phenanthroline (3) and meso-
boronic ester porphyrin 4, whereas in Route C the coupling
reactions occur directly on the phenanthroline nucleus by
using 2,9-dichloro-1,10-phenanthroline (5) and meso-phenyl
boronic ester porphyrin 6 as precursors. The various steps
involved in the preparation of the precursors of these three
synthetic ways are discussed below.
Route A: Synthesis of 1 by a Double Cyclisation Reaction
This is the oldest route explored in our group.[2g] It looks
to be the simplest one, as it is based on the direct synthesis
of free-base bis(porphyrin) 7 by two simultaneous Ro-
themund reactions under Adler conditions on phenanth-
roline 2 (Scheme 2).[8]
[a] Laboratoire de Chimie Organo-Minérale, Institut de Chimie,
LC3 UMR 7177 du CNRS, Université de Strasbourg,
4 rue Blaise Pascal, 67070 Strasbourg Cedex, France
E-mail: heitz@chimie.u-strasbg.fr
Phenanthroline 2 was prepared from 1,10-phenanth-
roline by a double nucleophilic aromatic substitution with
Eur. J. Org. Chem. 2009, 2801–2805
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2801

M. Beyler, C. Beemelmanns, V. Heitz, J.-P. Sauvage
FULL PAPER
Scheme 1. Different synthetic routes, A, B, and C, explored to synthesise zinc(II) bis(porphyrin) 1 and the corresponding precursors.
the lithium derivative of para-(5,5-dimethyl-1,3-dioxan-2-
yl)bromobenzene, followed by acidic hydrolysis of the acetal
to restore the aldehyde functional group, as described in the
literature.[9] When 2 was treated with 3,5-di-tert-butylbenz-
aldehyde and pyrrole in a 1:24:25 proportion in refluxing
propionic acid, free-base porphyrin 7 was obtained with a
very poor yield of 2–3% only. This yield was expected, as
porphyrins with four identical meso substituents are usually
obtained with yields not higher than 20% under Adler con-
ditions. Compound 7 can be quantitatively converted into
1 by double metallation of the two free-base porphyrins by
using zinc(II) acetate. Difficulties in isolating 7 from the
crude product (numerous and delicate chromatographic
separations) and the amount obtained (70 mg of 7 from
500 mg of 2) make this approach unattractive.
Route B: Synthesis of 1 by a Double Suzuki Cross-Coupling
Reaction of meso-Boronic Ester Porphyrin 4 and 2,9-Bis(4-
bromophenyl)-1,10-phenanthroline (3)
Several synthetic steps were necessary to construct 4, a
porphyrin with three meso aryl groups and a boronic ester
directly attached to the remaining meso position. The syn-
thesis started with the formation of 8 from dipyrrylmethane
and 3,5-di-tert-butylbenzaldehyde according to a literature
procedure.[10] Following a two-step reaction, monobromin-
ation and subsequent Suzuki coupling as described by Odo-
bel and co-workers,[11] 8 was converted into porphyrin 10.
After almost quantitative bromination of the remaining free
Scheme 2. Route A: Synthesis of free-base bis(porphyrin) 7 by a
double cyclisation reaction.
2802
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2801–2805

Various Synthetic Routes to a Gable-Like Bis(porphyrin)
meso position and zinc metallation of the central core, 11
was obtained (Scheme 3).[12] It was converted into boronic
ester 4 in 45% yield by using pinacolborane as the trans-
metallating reagent as developed by Masuda[13] under reac-
tion conditions described by Therien and co-workers[14] for
related porphyrins. Phenanthroline 3 was prepared by a
two-step procedure from 1,10-phenanthroline as described
by our group.[15] The final double Suzuki reaction involving
3 and 4 (2 equiv.) was performed under classical conditions
to give 1 in 53% yield after purification by column
chromatography.
Scheme 4. Route C: Synthesis of meso-phenyl boronic ester porphy-
rin 6 followed by Suzuki cross-coupling reaction with 5.
Phenanthroline 5 was prepared on a gram scale in three
steps from 1,10-phenanthroline monohydrate as already de-
scribed.[18] Pd-catalysed cross-coupling of 5 with 6 (2 equiv.)
gave desired zinc(II) bis(porphyrin) 1 in 75% yield, which
is a better yield than that obtained in the last step of
Route B also based on a double Suzuki cross-coupling reac-
tion to form 1.
Scheme 3. Route B: Synthesis of porphyrin precursor 4 and the
coupling reaction of 4 with phenanthroline derivative 3.
Conclusions
Route C: Synthesis of 1 by a Double Suzuki Cross-Coupling
Reaction between meso-Phenyl Boronic Ester Porphyrin 6
and 2,9-Dichloro-1,10-phenanthroline (5)
Three different routes to a zinc(II) bis(porphyrin) were
discussed. Whereas Route A might seem attractive because
the number of steps is limited, the low yield, the limited
This route required the synthesis of porphyrin 12, a meso amount of compound obtained, and the extreme separation
substituted porphyrin similar to 4, which can be obtained and purification difficulties make it almost useless.
easily in a one-step reaction by condensation of the appro- Routes B and C are based on a double Suzuki cross-coup-
priate aromatic aldehydes and pyrrole under Adler reaction ling reaction with various halogenated 1,10-phenanthroline
conditions.[8] Metallation with zinc(II) was performed di- and boronic ester porphyrin precursors. Route C is the most
rectly on the crude product obtained after workup. The efficient one, as the number of steps to construct the func-
yield of the isolated compound (10%) was better than that tionalised porphyrin is significantly less than that of
obtained under Lindsey conditions.[16] The moderate yield Route B. This new strategy paves the way to the construc-
was counterbalanced by the amount of 12, which can be tion of more complex multiporphyrin assemblies based on
obtained in one batch (typically 500 mg) and purification this readily available ligand. The zinc(II) porphyrins can co-
of the iodo porphyrin derivative is easier than that of the ordinate nitrogen-bearing ligands, and the phenanthroline
bromo derivative (i.e., 9; Scheme 3, Route B). From 12, chelates can be used to assemble several such bis(porphyrin)s
meso-phenyl boronic ester zinc(II) porphyrin 6 was ob- around a given transition-metal centre. A noncovalent tet-
tained by using the approach of Miyaura with pinacol di- raporphyrinic catenane was recently reported in the litera-
boron as the transmetallating reagent, as represented in ture[7] and other noncovalent multiporphyrinic edifices are
Scheme 4.[17]
actually elaborated by using this zinc(II) bis(porphyrin).
Eur. J. Org. Chem. 2009, 2801–2805
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2803

M. Beyler, C. Beemelmanns, V. Heitz, J.-P. Sauvage
FULL PAPER
(70 mL), and the mixture was heated at reflux for 6 h. The solvent
was removed by adding the same amount of toluene and by evapo-
rating the mixture under reduced pressure. The crude product was
taken up in dichloromethane and triethylamine (100 mL) was
added. Then, the mixture was washed with water (3ϫ50 mL), and
the organic layer was evaporated under reduced pressure and dried
under vacuum. The crude product was again taken up in dichloro-
methane and filtered by a column of silica gel in order to remove
the black polymers. The fractions containing the desired product
were then precipitated in CH2Cl2/EtOH and purified by column
chromatography (silica gel; cyclohexane/CH2Cl2, 100:0 to 80:20).
The desired porphyrin contaminated with impurities was metall-
ated with zinc acetate. The mixture was dissolved in dichlorometh-
ane, and Zn(OAc)2·2H2O (175 mg) dissolved in methanol (20 mL)
was added. The mixture was heated at reflux for 1 h, and then the
solvents were evaporated under reduced pressure. The crude was
taken up in dichloromethane and washed with water. The organic
layer was evaporated and dried under vacuum. Finally, flash col-
umn chromatography (several elutions; alumina; cyclohexane/
CH2Cl2, 98:2 to 90:10) gave 12 as a purple solid (490 mg, 10%).
1H NMR (300 MHz, CD2Cl2): δ = 9.00 (d, 3J = 4.6 Hz, 2 H,
Hpyrrolic), 8.99 (s, 4 H, Hpyrrolic), 8.94 (d, 3J = 4.6 Hz, 2 H, Hpyrrolic),
8.12 (d, 3J = 8.2 Hz, 2 H, Ho), 8.09 (d, 4J = 1.8 Hz, 6 H, Hopx,opz),
7.98 (d, 3J = 8.2 Hz, 2 H, Hm), 7.84 (m, 4J = 1.8 Hz, 3 H, Hppx,ppz),
1.53 (s, 54 H, HtBux,tBuz) ppm. MS (ES): m/z = 1040.43 [M]+.
Experimental Section
General Methods: Dry solvents were distilled from suitable drying
agents: 1,2-dimethoxyethane from sodium/benzophenone and 1,2-
dichloroethane from calcium hydride. Commercial anhydrous diox-
ane was purchased from Aldrich and used as received. Flash col-
umn chromatography was carried out by using Combi Flash Re-
trieve (alumina neutral chromatography columns by Teledyne Isco).
Column chromatography was carried out by using silica gel (Merck
Kieselgel, silica gel 60, 0.063–0.200 mm). All chemicals were of best
commercially available grade and used without further purification
(except when mentioned). NMR spectra for 1H were acquired with
a Bruker Avance 300 spectrometer. The spectra were referenced to
residual proton-solvent references (1H: CD2Cl2 at δ = 5.32 ppm).
In the assignments, the chemical shift (in ppm) is given first, fol-
lowed, in brackets, by the multiplicity of the signal (s: singlet, d:
doublet, t: triplet, m: multiplet, br. d: broad doublet), the value of
the coupling constants in Hertz if applicable, the number of pro-
tons implied, and finally the assignment. Mass spectra were ob-
tained with a Bruker MicroTOF spectrometer.
Compound 4: A round-bottom flask was charged with compound
11 (115 mg, 0.11 mmol), pinacolborane (140 µL, 0.95 mmol), tri-
ethylamine (200 µL, 1.49 mmol), dichlorobis(triphenylphosphane)-
palladium(II) (2.4 mg, 0.003 mmol), and freshly distilled 1,2-
dichloroethane (20 mL). The mixture was degassed by three vac-
uum–argon cycles and then stirred at 90 °C under an atmosphere
of argon. After 2 h, thin-layer chromatography showed complete
conversion of 11. The solvent was evaporated; the residue was
taken up in dichloromethane and washed with water. The organic
layer was dried with magnesium sulfate. The solvent was evapo-
rated, and the crude product was purified by a quick column
chromatography (silica gel; pentane/CH2Cl2, 70:30) to yield 4 as a
purple solid (53 mg, 45%). 1H NMR (300 MHz, CD2Cl2): δ = 9.91
Compound 6: A round-bottom flask was charged with compound
12 (200 mg, 0.18 mmol), bis(pinacolato)diboron (67 mg, 0.26
mmol), potassium acetate (52 mg, 0.53 mmol), [1,1Ј-bis(diphenyl-
phosphanyl)ferrocene]dichloropalladium(II) (7.2 mg, 0.009 mmol),
and commercial anhydrous dioxane (2 mL). The mixture was de-
gassed by three vacuum–argon cycles and then stirred at 80 °C un-
der an atmosphere of argon. The reaction was monitored by thin-
layer chromatography, and after 5 d, no more evolution could be
detected. The solvent was removed under reduced pressure, and the
crude product was taken up in dichloromethane and washed with
water (3ϫ10 mL). The crude product was then purified by flash
column chromatography (silica gel; cyclohexane/CH2Cl2, 65:35) to
3
(d, J = 4.5 Hz, 2 H, Hpyrrolic), 9.10 (d, 3J = 4.8 Hz, 2 H, Hpyrrolic),
9.00 (d, 3J = 4.8 Hz, 2 H, Hpyrrolic), 8.99 (d, 3J = 4.8 Hz, 2 H,
4
4
H
pyrrolic), 8.12 (d, J = 1.8 Hz, 4 H, Hopx), 8.09 (d, J = 1.8 Hz, 2
4
4
H, Hopz), 7.87 (t, J = 1.8 Hz, 2 H, Hppx), 7.84 (t, J = 1.8 Hz, 1
H, Hppz), 1.86 (s, 12 H, HMe-boronic), 1.56 (s, 36 H, HtBux), 1.53 (s,
18 H, HtBuz) ppm. MS (ES): m/z = 1065.58 [M + H]+.
1
yield 50% of 6 as a purple solid. H NMR (300 MHz, CD2Cl2): δ
3
= 9.06 (s, 4 H, Hpyrrolic), 9.05 (d, J = 4.5 Hz, 2 H, Hpyrrolic), 8.99
ZnII Bis(porphyrin) 1 by Route B: A Schlenk flask was charged with
(d, 3J = 4.8 Hz, 2 H, Hpyrrolic), 8.31 (d, 3J = 8.1 Hz, 2 H, Ho), 8.20
(d, 3J = 7.8 Hz, 2 H, Hm), 8.17 (d, 4J = 1.8 Hz, 6 H, Hopx,opz), 7.91
porphyrin derivative
4
(137 mg, 0.13 mmol),
3
(21 mg,
4
0.043 mmol), barium hydroxide octahydrate (40.6 mg, 0.13 mmol),
freshly distilled 1,2-dimethoxyethane (3.5 mL), and deionised water
(0.35 mL). The mixture was freeze–pump–thaw degassed before tet-
rakis(triphenylphosphane)palladium (5 mg, 0.0043 mmol) was
added, and the mixture was then stirred at reflux under an atmo-
sphere of argon overnight. The solvents were evaporated, and the
residue was taken up in dichloromethane and washed with water.
The organic layer was dried under vacuum. The crude product was
then purified by column chromatography three times (2ϫsilica gel;
pentane/CH2Cl2, 100:0 to 50:50; then 1ϫsilica gel; cyclohexane/
CH2Cl2, 80:20 to 50:50) to give 1 as a purple solid (50 mg, 53%).
1H NMR (300 MHz, CD2Cl2): δ = 9.06 (d, 3J = 4.6 Hz, 4 H,
(t, J = 1.8 Hz, 3 H, Hppx,ppz), 1.60 (s, 54 H, HtBux,tBuz), 1.53 (s, 12
H, HMe-boronic) ppm. MS (ES): m/z 1141.53 [M + H]+.
ZnII Bis(porphyrin) 1 by Route C: A Schlenk flask was charged with
compound 6 (133.2 mg, 0.12 mmol), 5 (13.6 mg, 0.056 mmol), bar-
ium hydroxide octahydrate (36 mg, 0.12 mmol), freshly distilled 1,2-
dimethoxyethane (2.6 mL), and deionised water (0.26 mL). The
mixture was freeze–pump–thaw degassed before tetrakis(triphenyl-
phosphane)palladium (13.5 mg, 0.012 mmol) was added, and the
mixture was stirred at reflux under an atmosphere of argon over-
night. The solvents were evaporated, and the residue was taken up
in dichloromethane and washed with water (3ϫ10 mL). The or-
ganic layer was dried under vacuum. The crude product was then
purified by column chromatography (silica gel; cyclohexane/
CH2Cl2, 60:40 to 20:80) and precipitated with CH2Cl2/MeOH to
yield 1 as a purple solid (93 mg, 75%). Compound 1 was character-
ised as described in Route B.
3
3
Hpyrrolic), 8.94 (d, J = 4.6 Hz, 8 H, Hpyrrolic), 8.92 (d, J = 4.6 Hz,
4 H, Hpyrrolic), 8.92 (d, 3J = 8.3 Hz, 4 H, Ho), 8.56 (br. d, 4 H,
3
4
H3,4,7,8), 8.50 (d, J = 8.1 Hz, 4 H, Hm), 8.11 (d, J = 1.7 Hz, 4 H,
4
Hopz), 8.06 (d, J = 1.8 Hz, 8 H, Hopx), 8.01 (s, 2 H, H5,6), 7.86 (t,
4J = 1.7 Hz, 2 H, Hppz), 7.79 (t, J = 1.7 Hz, 4 H, Hppx), 1.55 (s,
4
36 H, HtBuz), 1.47 (s, 72 H, HtBux) ppm. MS (ES): m/z = 2206.09
[M + H]+.
Acknowledgments
Compound 12: In a round-bottom flask, 4-iodobenzaldehyde (1.1 g,
0.0047 mmol), 3,5-di-tert-butylbenzaldehyde (4.9 g, 0.023 mmol),
and pyrrole (1.3 mL, 0.02 mmol) were dissolved in propionic acid
We thank Dr. T. Ljungdahl for his early contribution to the syn-
thetic work. We thank also the Centre National de la Recherche
2804
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2801–2805

Various Synthetic Routes to a Gable-Like Bis(porphyrin)
261; e) J. A. Faiz, V. Heitz, J.-P. Sauvage, Chem. Soc. Rev. 2009,
38, 422–442.
[6] E. Iengo, E. Zangrando, E. Alessio, J.-C. Chambron, V. Heitz,
L. Flamigni, J.-P. Sauvage, Chem. Eur. J. 2003, 9, 5879–5887.
[7] M. Beyler, V. Heitz, J.-P. Sauvage, Chem. Commun. 2008, 5396–
5398.
[8] A. D. Adler, F. R. Longo, J. D. Finarelli, J. Goldmacher, J. Ass-
our, L. Korsakoff, J. Org. Chem. 1967, 32, 476.
[9] M. Linke, J.-C. Chambron, V. Heitz, J.-P. Sauvage, S. Encinas,
F. Barigelletti, L. Flamigni, J. Am. Chem. Soc. 2000, 122,
11834–11844.
[10] a) C.-H. Lee, J. S. Lindsey, Tetrahedron 1994, 50, 11427–11440;
b) B. J. Littler, M. A. Miller, C.-H. Hung, R. W. Wagner, D. F.
O’Shea, P. D. Boyle, J. S. Lindsey, J. Org. Chem. 1999, 64,
1391–1396.
[11] F. Odobel, S. Suresh, E. Blart, Y. Nicolas, J.-P. Quintard, P.
Janvier, J.-Y. Le Questel, B. Illien, D. Rondeau, P. Richomme,
T. Häupl, S. Wallin, L. Hammarström, Chem. Eur. J. 2002, 8,
3027–3046.
[12] K. Kurotobi, A. Osuka, Org. Lett. 2005, 7, 1055–1058.
[13] M. Murata, S. Watanabe, Y. Masuda, J. Org. Chem. 1997, 62,
6458–6459.
[14] G. Hyslop, M. A. Matthew, A. Kellett, P. M. Iovine, M. J.
Therien, J. Am. Chem. Soc. 1998, 120, 12676–12677.
[15] C. Dietrich-Buchecker, B. Colasson, M. Fujita, A. Hori, N.
Geum, S. Sakamoto, K. Yamaguchi, J.-P. Sauvage, J. Am.
Chem. Soc. 2003, 125, 5717–5725.
[16] N. Solladié, M. Gross, Tetrahedron Lett. 1999, 40, 3359–3362.
[17] T. Ishiyama, M. Murata, N. Miyaura, J. Org. Chem. 1995, 60,
7508–7510.
Scientifique (CNRS) for financial support. We acknowledge the
French Ministry of Education for a fellowship (M. B.).
[1]
[2]
K. M. Kadish, K. M. Smith, R. Guilard (Eds.), The Porphyrin
Handbook, Academic press, San Diego, CA, 2000, vol. 1, ch. 1
and 2.
a) I. Tabushi, T. Sasaki, J. Am. Chem. Soc. 1983, 105, 2901–
2902; b) I. Tabushi, S. Kugimiya, M. G. Kinnaird, T. Sasaki, J.
Am. Chem. Soc. 1985, 107, 4192–4199; c) I. Tabushi, S. Kugi-
miya, T. Sasaki, J. Am. Chem. Soc. 1985, 107, 5159–5163; d)
J. L. Sessler, J. Hugdahl, M. R. Johnson, J. Org. Chem. 1986,
51, 2838–2840; e) H. Meier, Y. Kobuke, S. Kugimiya, J. Chem.
Soc., Chem. Commun. 1989, 923–924; f) S. Kugimiya, J. Chem.
Soc., Chem. Commun. 1990, 432–434; g) S. Chardon-Noblat,
J.-P. Sauvage, Tetrahedron 1991, 47, 5123–5132; h) V. Heitz, S.
Chardon-Noblat, J.-P. Sauvage, Tetrahedron Lett. 1991, 32,
197–198; i) A. Osuka, B. L. Liu, K. Maruyama, J. Org. Chem.
1993, 58, 3582–3585; j) S. Ito, K. Nakamoto, H. Uno, T. Mura-
shima, N. Ono, Chem. Commun. 2001, 2696–2697; k) T. Mizut-
ani, K. Wada, S. Kitagawa, Chem. Commun. 2002, 1626–1627;
l) L. La Monica, D. Monti, J. Porphyrins Phthalocyanines 2002,
6, 58–65; m) Y. Kuramochi, A. Satake, M. Itou, K. Ogawa, Y.
Araki, O. Ito, Y. Kobuke, Chem. Eur. J. 2008, 14, 2827–2841.
[3] I. Tabushi, T. Sasaki, Tetrahedron Lett. 1982, 23, 1913–1916.
[4] J. Deisenhofer, O. Epp, K. Miki, R. Huber, H. Michel, J. Mol.
Biol. 1984, 180, 385–398.
[5] a) J.-C. Chambron, A. Harriman, V. Heitz, J.-P. Sauvage, J.
Am. Chem. Soc. 1993, 115, 7419–7425; b) M.-J. Blanco, M. C.
Jimenez, J.-C. Chambron, V. Heitz, M. Linke, J.-P. Sauvage, [18] a) J. Frey, T. Kraus, V. Heitz, J.-P. Sauvage, Chem. Eur. J. 2007,
Chem. Soc. Rev. 1999, 28, 293–305; c) L. Flamigni, A. M. Tal-
arico, J.-C. Chambron, V. Heitz, M. Linke, N. Fujita, J.-P.
Sauvage, Chem. Eur. J. 2004, 10, 2689–2699; d) L. Flamigni, V.
Heitz, J.-P. Sauvage, Struct. Bonding (Berlin) 2006, 121, 217–
13, 7584–7594; b) J. E. Dickeson, L. A. Summers, Aust. J.
Chem. 1970, 23, 1023–1027.
Received: February 12, 2009
Published Online: April 21, 2009
Eur. J. Org. Chem. 2009, 2801–2805
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2805