Efficient rhodium-catalyzed installation of unsaturated ester functions onto porphyrins: Site-specific heck-type addition versus conjugate addition

Article abstract of DOI:10.1002/chem.200701943

A facile introduction of α,β-or α,β,γ,δ- unsaturated ester functions onto porphyrins was achieved through rhodium-catalyzed addition of β-boryl-porphyrins to acrylate or 2,4-penta-dienoate esters. The reaction of meso-borylporphyrins with acrylates exclusively afforded saturated esters by 1,4-conjugate addition under the same reaction conditions. Thus, the reaction mode (Heck-type versus conjugate addition) is highly dependent on the reaction site (β versus meso). This functionalization has a significant impact on the electronic properties of the π system of porphyrins, which induces a substantial redshift and broadening in the absorption spectra by effective conjugation through the β positions. The coplanar structure of the unsaturated ester moieties with respect to the porphyrin core has been unambiguously elucidated by X-ray crystallographic analysis.

Full text of DOI:10.1002/chem.200701943

DOI: 10.1002/chem.200701943
Efficient Rhodium-Catalyzed Installation of Unsaturated Ester Functions
onto Porphyrins: Site-Specific Heck-Type Addition versus Conjugate
Addition
Hiromi Baba, Jinping Chen, Hiroshi Shinokubo,* and Atsuhiro Osuka*[a]
Abstract: A facile introduction of a,b-
or a,b,g,d-unsaturated ester functions
onto porphyrins was achieved through
rhodium-catalyzed addition of b-boryl-
porphyrins to acrylate or 2,4-penta-
mode (Heck-type versus conjugate ad-
dition) is highly dependent on the reac-
tion site (b versus meso). This function-
alization has a significant impact on
system of porphyrins, which induces a
substantial redshift and broadening in
the absorption spectra by effective con-
jugation through the b positions. The
coplanar structure of the unsaturated
ester moieties with respect to the por-
phyrin core has been unambiguously
elucidated by X-ray crystallographic
analysis.
the electronic properties of the
p
A
borylporphyrins with acrylates exclu-
sively afforded saturated esters by 1,4-
conjugate addition under the same re-
action conditions. Thus, the reaction
À
Keywords: boron · C C coupling ·
Heck reaction
rhodium
·
porphyrinoids
·
Introduction
carbon bond formation with high levels of asymmetric in-
duction.[7]
Peripheral functionalization is important for the modifica-
tion of porphyrins and thus the fine-tuning of their electron-
ic and photophysical properties. Most porphyrin functionali-
zations rely on classical but still useful electrophilic substitu-
tion such as halogenation, formylation, and nitration.[1] As
for modern transition metal-catalyzed reactions, palladium-
catalyzed cross coupling[2] as well as Sonogashira[3] and
Heck reactions[4] are powerful tools for the further derivati-
zation of haloporphyrins.[5] However, rhodium-catalyzed
transformations have never been employed in porphyrin
synthesis, although they have proven to be highly versatile
in organic synthesis.[6] In particular, the chemistry of organo-
boranes combined with rhodium catalysis has been exten-
sively explored in the search for new types of carbon–
For the synthesis of a functionalized porphyrin, protected
functional groups are often introduced into the porphyrin
precursor, such as dipyrromethanes and aldehydes, before
cyclization. However, the protected functional group is
sometimes decomposed to some extent under the acidic and
oxidative conditions of porphyrin synthesis. We propose the
post-modification of relatively simple porphyrins by organo-
metallic and catalytic means.[8] Herein, we report facile and
efficient installation of carboxylic ester functions at the
meso and b positions of porphyrins by the rhodium-cata-
A
lyzed addition of organoboranes to acrylates as the first ap-
plication of rhodium catalysis to porphyrin synthesis. In par-
ticular, the use of b-boryl porphyrins allows the multiple in-
troduction of a,b- and a,b,g,d-unsaturated ester groups,
which are effectively conjugated to the porphyrin p system,
at the b positions in a sterically unhindered manner.[9]
Selective introduction of ester groups at desired positions
in porphyrins is quite important because carboxylic acid
groups attached to porphyrins serve as anchoring moieties
to ensure efficient absorption on the surface of TiO2, a pro-
cess that enhances the efficiency of dye-sensitized solar cells
(DSSC).[10,11] Furthermore, carboxylic acid functions act as
hydrophilic sites in water-soluble porphyrins, which are
useful materials in photodynamic therapy and often exhibit
intriguing aggregation properties in water.[12]
[a] H. Baba, Dr. J. Chen, Prof. Dr. H. Shinokubo, Prof. Dr. A. Osuka
Department of Chemistry
Graduate School of Science
Kyoto University
Sakyo-ku, Kyoto 606-8502 (Japan)
Fax : (+81)75-753-3970
E-mail: hshino@kuchem.kyoto-u.ac.jp
osuka@kuchem.kyoto-u.ac.jp
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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Chem. Eur. J. 2008, 14, 4256 – 4262

FULL PAPER
Results and Discussion
Site-specific Rh-catalyzed addition of b- and meso-boryl
porphyrins: b-Boryl porphyrins were prepared by means of
direct, regioselective iridium-catalyzed b-borylation of por-
phyrins.[8a,c] meso-Boryl porphyrins were synthesized accord-
ing to Therienꢁs protocol.[13] b-Boryl porphyrin 1 was heated
at 1008C for 15 h in aqueous 1,4-dioxane with hexyl acrylate
(10 equiv) in the presence of 10 mol% of [{Rh(cod)(OH)}2]
G
(cod=1,5-cyclooctatriene). After chromatographic separa-
tion, unsaturated ester 2 was obtained in 82% yield along
with a small amount of saturated product (<3%), which
clearly indicated that predominant addition–elimination,
namely Heck-type addition, had proceeded (Scheme 1).[14]
Scheme 2. Reaction mechanism.
en-3-one, afforded only saturated products 8 and 9 in 89 and
77% yields, respectively. This indicates that only conjugate
addition occurs in the reaction with the a,b-enone regardless
of the position of the boryl group. The reaction with methyl
2,4-pentadienoate allowed further elongation of conjugation
through selective 1,6-addition (Scheme 3).[17] Conjugate ad-
dition competed with Heck-type addition to provide a mix-
ture of products 10 and 11, but the crude mixture was selec-
tively transformed into fully conjugated product 10 in 70%
overall yield upon treatment with DDQ. Interestingly, the
use of ZnII–porphyrin 1–Zn resulted in exclusive formation
of conjugated product 10–Zn.[18] Clearly, the central metal
has a significant effect on the selectivity of the reaction
course, probably by changing the electron density of the por-
Scheme 1. Site-specific Rh-catalyzed addition of b- and meso-boryl por-
phyrins to acrylate. Ar=3,5-di-tert-butylphenyl.
In contrast, the reaction of meso-boryl porphyrin 3 under
exactly the same conditions exclusively provided saturated
product 4 in 73% yield by 1,4-conjugate addition).[15] Nota-
bly, the reaction mode (Heck-type addition versus conjugate
addition) was highly dependent on the reaction site (b
versus meso).
phyrin core. This is also the case for diborylporphyrins:
C
In view of the reaction mechanism, it is worth noting that
the reaction mode of these rhodium-catalyzed addition reac-
tions is highly dependent on the reaction site in the porphyr-
ins. The transition states for the b-elimination steps were
calculated by DFT at the B3LYP/LANL2DZ level (see the
Supporting Information). Calculations were carried out by
using the Gaussian 03 program.[16] Whereas b elimination
occurs smoothly in transition-state A from b-boryl porphy-
rin, b elimination is not favorable from the meso-boryl por-
phyrin due to steric repulsion between the adjacent b
proton in transition-state B (Scheme 2). The intermediate is
then hydrolyzed to provide the conjugate addition product
via oxa-p-allylrhodium species C.
The use of b,b’-diboryl- and b,b’b’’,b’’’-tetraborylporphyrin
provided diester 5 and tetraester 6 in 72 and 68% yield, re-
spectively, by Heck-type addition. meso,meso’-Diboryl por-
phyrin underwent exclusive 1,4-conjugate addition to furnish
the corresponding saturated ester 7 in 61% yield. Interest-
ingly, the reaction with the a,b-unsaturated ketone, oct-1-
Chem. Eur. J. 2008, 14, 4256 – 4262
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4257

H. Shinokubo, A. Osuka, et al.
Scheme 3. Rh-catalyzed addition of b-boryl porphyrins to methyl penta-
dienoate. DDQ=2,3-dichloro-5,6-dicyano-1,4-benzoquinone; Ar=3,5-di-
tert-butylphenyl.
tained in only 10% yield even after the use of DDQ in the
reaction with the corresponding free base porphyrin.
X-ray crystallographic analysis and electronic absorption
properties: The structures of b,b’- and meso,meso’-diester
porphyrins were unambiguously elucidated by X-ray crystal-
lographic analysis (Figure 1). In the case of 5, the b-unsatu-
rated ester moieties adopt a rather coplanar conformation
and the dihedral angles of C3-C2-C63-C64 and C17-C18-
C72-C73 are 2.5 and 22.28, respectively, because of the lack
of steric bulkiness at the meso position. This orientation
allows effective electronic conjugation in the porphyrin p
Figure 1. X-ray structures of 5, 7, and 9. a) Top view and b) side view of
5, c) top view of 7, and d) top view of 9. The thermal ellipsoids are at the
50% probability level. The meso-aryl and alkyl groups in b) are omitted
for clarity.
À
system, which is confirmed by the shortened Cpyrrole Cvinyl
single bond lengths (1.447(7) and 1.448(7) Š) relative to the
À
Cpyrrole Csp3 single bond lengths (1.508(3) Š) in diketo por-
phyrin 9. In contrast, the meso-ester substituents in 7 are
perpendicular to the porphyrin plane to minimize the steric
repulsion between the proximal b-hydrogen atoms.
sitions in porphyrins are quite significant and the shapes of
the absorption bands of 10 and 12 are much broader and are
redshifted, which implies their prospective use as light-har-
vesting dyes. In comparison with the parent triarylporphyrin,
the redshift reaches 44 nm (Soret band) in the case of 12 by
the introduction of two conjugated dienoate moieties. The
full widths at half maxima (fwhm) of the Soret bands of 10
and 12 are 2350 and 2180 cmÀ1, respectively. The shape of
the absorption spectrum of 10 in dichloromethane does not
As is evident from the X-ray structure, the lack of bulky
meso-substituents secures the extension of conjugation at
the b positions. In fact, b-enoate porphyrins 2, 5, and 6 ex-
hibit substantial redshifts and broadening of the Soret and
Q bands in the absorption spectra (Figure 2a,b). Further-
more, the electronic effects of dienoate moieties at the b po-
4258
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Chem. Eur. J. 2008, 14, 4256 – 4262

Rh-Catalyzed Installation of Ester Functions onto Porphyrins
FULL PAPER
show any notable change in the range from 4.0”10À7 to
8.0”10À6 molLÀ1. The considerable broadening in the spec-
trum is probably explained by its lower symmetry and the
electronic effect of the enoate moiety rather than by the for-
mation of aggregates of 10. Fluorescence spectra of these
porphyrins are also redshifted by the introduction of the un-
saturated substituents (Figure 2c,d). In contrast, no signifi-
cant affects on the absorption properties by meso-substitu-
tion were observed in 7 and 8 (see the Supporting Informa-
tion).
Synthesis of water-soluble porphyrin 13: Saponification of
tetraester porphyrin 6 under standard conditions provided
tetraacid 13 in quantitative yield. Absorption spectra of tet-
raacid 13 in THF and basic water are shown in Figure 3. The
blueshift of the Soret band in basic water can be accounted
for by formation of H-aggregates due to the hydrophobic
effect and p–p stacking interactions.
Figure 3. UV/Vis absorption spectra of 13 in THF (c) and basic water
(a).
Conclusion
We have demonstrated an efficient introduction of ester
functions onto porphyrins by the addition of borylporphy-
rins to acrylates. This is the first application of rhodium-cat-
alyzed transformations of organoboranes in porphyrin syn-
thesis. Interestingly, the reaction mode (Heck-type versus
conjugate addition) depends heavily on the reaction site (b
versus meso) in the porphyrins. The unsaturated ester
moiety has a significant impact on the electronic system of
the porphyrin by effective conjugation at the b positions.
This reaction will be useful for the introduction of long alkyl
chains to enhance solubility and control aggregation proper-
ties in the condensed phase by the use of properly designed
acrylate esters. Moreover, the unsaturated ester moieties in-
troduced in this way would be a nice foothold for further
functionalization. Application of the materials obtained
here in dye-sensitized solar cells is currently underway.
Figure 2. UV/Vis absorption spectra (CH2Cl2) of a) 2 (a), 5 (b), and
6 (c) and b) 10 (a; M=H2) and 12 (c; M=H2) and fluorescence
spectra (CH2Cl2) of c) 2 (a), 5 (b), and 6 (c) and d) 10 (a;
M=H2) and 12 (c; M=H2). The corresponding spectra of 5,10,15-
tris(3,5-di-tert-butylphenyl)porphyrin (c) are shown in all cases.
Chem. Eur. J. 2008, 14, 4256 – 4262
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4259

H. Shinokubo, A. Osuka, et al.
1.54 (s, 36H; tBu), 1.56 (s, 18H; tBu), 1.84–1.89 (m, 2H; Hex), 4.41 (t,
J=6.9 Hz, 2H; Hex), 7.14 (d, J=15.6 Hz, 1H), 7.79 (t, J=1.4 Hz, 1H;
Ar-para-H), 7.81 (t, J=1.4 Hz, 1H; Ar-para-H), 7.84 (t, J=1.8 Hz, 1H;
Ar-para-H), 8.04 (d, J=1.4 Hz, 2H; Ar-ortho-H), 8.09 (t, J=1.9 Hz, 4H;
Ar-ortho-H), 8.86 (d, J=4.6 Hz, 1H; b-H), 8.89 (d, J=4.6 Hz, 1H; b-H),
8.91 (d, J=5.0 Hz, 1H; b-H), 8.93 (d, J=4.6 Hz, 1H; b-H), 9.07 (d, J=
4.1 Hz, 1H; b-H), 9.23 (s, 1H; b-H), 9.38 (d, J=15.1 Hz, 1H), 9.40 (d,
J=6.0 Hz, 1H; b-H), 10.37 ppm (s, 1H; meso); UV/Vis (CH2Cl2): lmax
(e)=434 (2.52”105), 522 (2.08”104), 559.5 (9.11”103), 598 (8.22”103),
654.5 nm (5.59”103 mÀ1 cmÀ1); fluorescence (CH2Cl2), lex =434; lem =658,
723 nm; HRMS(ESI): m/z: calcd for C71H88N4O2Na: 1051.6799 [M+Na]+;
found: 1051.6799.
Experimental Section
Instrumentation and materials: 1H NMR (600 MHz) spectra were mea-
sured on a JEOL ECA-600 spectrometer, and chemical shifts were re-
ported on the d scale in ppm relative to CHCl3 (d=7.260 ppm). UV/Vis
absorption spectra were recorded on a Shimadzu UV-3150 spectrometer.
Mass spectra were recorded on
a Shimadzu/KRATOS KOMPACT
MALDI spectrometer by using the positive-MALDI ionization
4
method. High resolution ESI-TOF mass spectra were measured on a
Bruker microTOF instrument. Recycling preparative GPC-HPLC was
carried out on a JAI LC-908 instrument with preparative JAIGEL-2H
and 2.5H columns. Unless otherwise noted, materials obtained from com-
mercial suppliers were used without further purification.
n-Hexyl
3-[10,20-bis(3,5-di-tert-butylphenyl)porphyrin-5-yl]propanoate
(4): 1H NMR (600 MHz, CDCl3): d=À2.97 (s, 2H; NH), 0.81 (t, J=
6.8 Hz, 3H; Hex), 1.19–1.23 (m, 4H; Hex), 1.27–1.30 (m, 2H; Hex), 1.56
(s, 36H; tBu), 1.58–1.63 (m, 2H; Hex), 3.58 (t, J=8.3 Hz, 2H), 4.20 (t,
J=6.9 Hz, 2H), 5.47 (t, J=8.3 Hz, 2H), 7.83 (t, J=1.8 Hz, 2H; Ar-para-
H), 8.10 (d, J=1.86, 4H; Ar-ortho-H), 9.01 (d, J=4.6 Hz, 2H; b-H), 9.04
(d, J=4.6 Hz, 2H; b-H), 9.28 (d, J=4.1 Hz, 2H; b-H), 9.58 (d, J=4.6 Hz,
Crystallographic data collection and structure refinement: Data collec-
tion was carried out at low temperature (À1538C) on a Rigaku RAXIS-
RAPID instrument with graphite monochromated MoKa radiation (l=
0.71069 Š). Details of the crystallographic data are listed in Table 1. The
structures were solved by direct methods (SHELXS-97[19]) by using the
full-matrix least square technique (SHELXL-97).[19] CCDC 646245 (5),
646246 (7), and 646247 (9) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
2H; b-H), 10.12 ppm (s, 1H; meso); HRMS(EIS):
C57H71N4O2: 843.5572 [M+H]+; found: 843.5551.
m/z: calcd for
Di-n-hexyl (E,E)-3,3’-[5,10,15-tris(3,5-di-tert-butylphenyl)porphyrin-2,18-
diyl]diprop-2-enoate (5): 1H NMR (600 MHz, CDCl3): d=À2.53 (s, 2H;
NH), 0.94 (t, J=6.9 Hz, 6H; Hex), 1.38–1.42 (m, 8H; Hex), 1.49–1.53
(m, 4H; Hex), 1.53 (s, 18H; tBu), 1.54 (s, 36H; tBu), 1.84–1.89 (m, 4H;
Hex), 4.41 (t, J=6.9 Hz, 4H; OCH2), 7.15 (d, J=15.6 Hz, 2H), 7.77 (t,
J=1.9 Hz, 1H; Ar-para-H), 7.84 (t, J=1.9 Hz, 2H; Ar-para-H), 8.01 (d,
J=1.9 Hz, 2H; Ar-ortho-H), 8.06 (d, J=1.9 Hz, 4H; Ar-ortho-H), 8.84
(d, J=4.6 Hz, 2H; b-H), 8.85 (d, J=4.6 Hz, 2H; b-H), 9.22 (s, 2H; b-H),
9.37 (d, J=15.6 Hz; 2H), 10.43 ppm (s, 1H; meso); UV/Vis (CH2Cl2):
lmax (e)=449 (2.67”105), 535 (2.25”104), 571 (7.48”103), 609.5 (7.48”
General procedure: Borylated porphyrin (1, 40.9 mg, 41 mmol) and [{Rh-
(cod)(OH)}2] (1.8 mg, 4 mmol) were placed in a Schlenk flask, which was
A
evacuated and then purged with argon five times. Hexyl acrylate (70 mL,
0.4 mmol) followed by 1,4-dioxane/water (1.5/0.15 mL) were introduced
by using a syringe. The mixture was then stirred at 1008C for 16 h. The
reaction mixture was cooled to room temperature, diluted with CH2Cl2,
and filtered through a small plug of silica gel with copious washings
(CH2Cl2). After removal of the solvent in vacuo, the residue was purified
by silica-gel, column chromatography (hexane/CH2Cl2) and careful re-
crystallization (methanol/dichloromethane) to afford the Heck product 2
(34.7 mg, 34 mmol; 82%).
103), 668 nm (2.08”103 mÀ1 cmÀ1); fluorescence (CH2Cl2): lex =449; lem
=
671, 740 nm; HRMS(EIS):
m/z: calcd for C80H102N4O4Na: 1205.7793
[M+Na]+; found: 1205.7791.
Tetraethyl (E,E,E,E)-3,3’,3’’,3’’’-[5,15-bis(3,5-di-tert-butylphenyl)porphyr-
in-2,8,12,18-tetrayl]tetraprop-2-enoate (6): 1H NMR (600 MHz, CDCl3):
d=À2.39 (s, 2H; NH), 1.52 (t, J=6.9 Hz, 12H; CH3), 1.59 (s, 36H; tBu),
4.49 (q, J=6.8 Hz, 8H; OCH2), 7.15
n-Hexyl (E)-3-[5,10,15-tris(3,5-di-tert-butylphenyl)porphyrin-2-yl]prop-2-
enoate (2): 1H NMR (600 MHz, CDCl3): d=À2.72 (s, 2H; NH), 0.97 (t,
J=7.1 Hz, 3H; Hex), 1.40–1.43 (m, 4H; Hex), 1.50–1.52 (m, 2H; Hex),
(d, J=15.6 Hz, 4H), 7.91 (t, J=
1.8 Hz, 2H; Ar-para-H), 8.06 (d, J=
Table 1. Crystallographic data for 5, 7, and 9.
5
7
9
1.9 Hz, 4H; Ar-ortho-H), 9.20 (s, 4H;
b-H), 9.33 (d, J=15.6 Hz, 4H),
10.43 ppm (s, 2H; meso); UV/Vis
(CH2Cl2): lmax (e)=460 (2.65”105),
544 (2.73”104), 581.5 (1.24”104), 619
empirical formula
M
crystal system
space group
a [Š]
b [Š]
c [Š]
a [8]
b [8]
C
80.98H103.96Cl0.98N4O4
C66H83.80N4O4Zn
1062.54
triclinic
C80H106Cl2N4O2
1226.59
triclinic
1232.24
triclinic
P1 (2)
¯
¯
¯
P1 (2)
P1 (2)
(1.01”104),
678.5 nm
(4.17”
11.955(3)
17.381(5)
18.601(6)
84.117(10)
80.176(9)
71.333(9)
3603.1(18)
2
1.136
0.104 (MoKa
1333
0.10”0.10”0.10
55.0
123(2)
12504
5405
5.774(3)
14.425(7)
17.283(9)
94.571(18)
90.653(17)
90.721(16)
1434.6(11)
1
1.230
0.480 (MoKa
570
0.45”0.10”0.10
55.0
123(2)
14121
6463
12.937(5)
17.159(7)
17.616(9)
82.555(17)
68.410(14)
74.705(12)
3505(3)
2
1.142
0.142 (MoKa
1328
040”0.40”0.20
55.0
103 mÀ1 cmÀ1); fluorescence (CH2Cl2):
lex =460.5; lem =681, 755 nm; HRMS
(ESI): m/z: calcd for C68H78N4O8Na:
1101.5712
1101.5728.
[M+Na]+;
found:
g [8]
V [Š3]
Z
Di-n-hexyl 3,3’-[10,20-bis(3,5-di-tert-
butylphenyl)porphyrinate(zinc)-5,15-
AHCTREUNG
1calcd [gcmÀ3
]
diyl]dipropanoate (7): d=1H NMR
(600 MHz, CDCl3): d=0.80 (t, J=
7.1 Hz, 6H; Hex), 1.19–1.23 (m, 8H;
Hex), 1.26–1.30 (m, 4H; Hex), 1.56
(s, 36H; tBu), 1.59–1.63 (m, 4H;
Hex), 3.58 (t, J=8.3 Hz, 4H), 4.19 (t,
J=6.6 Hz, 4H; Hex), 5.41 (t, J=
8.3 Hz, 4H), 7.82 (t, J=1.9 Hz, 2H;
Ar-para-H), 8.07 (d, J=1.4 Hz, 4H;
Ar-ortho-H), 9.05 (d, J=4.6 Hz, 4H;
b-H), 9.59 ppm (d, J=4.6 Hz, 4H; b-
m [mmÀ1
(000)
]
)
)
)
F
ACHTREUNG
crystal size [mm3]
2qmax [8]
T [K]
123(2)
31920
15340
15340
903
total reflections
unique reflections
reflection used
parameters
absorption correction
R1
5405
918
none
0.0959
0.2893
1.011
6463
375
none
0.0836
0.2426
1.065
none
0.0605
0.2189
0.985
H); HRMS(EIS):
m/z: calcd for
wR2
GOF
C66H85N4O4Zn: 1061.5857 [M+H]+;
found: 1061.5854.
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Chem. Eur. J. 2008, 14, 4256 – 4262

Rh-Catalyzed Installation of Ester Functions onto Porphyrins
FULL PAPER
5,15-Bis(3,5-di-tert-butylphenyl)-10,20-bis(3-oxooctyl)porphyrinate
zinc(II) (8): 1H NMR (600 MHz, CDCl3): d=0.85 (t, J=6.9 Hz, 6H;
Pen), 1.25–1.28 (m, 8H; Pen), 1.55 (s, 36H; tBu), 1.64–1.69 (m, 4H;
Pen), 2.48 (t, J=7.3 Hz, 4H), 3.69 (t, J=8.2 Hz, 4H), 5.34 (t, J=7.8 Hz,
4H), 7.82 (d, J=1.8 Hz, 2H; Ar-para-H), 8.06 (d, J=1.9 Hz, 4H; Ar-
ortho-H), 9.03 (d, J=4.6 Hz, 4H; b-H), 9.53 ppm (d, J=4.6 Hz, 4H; b-
H); HRMS(ESI): m/z: calcd for C64H80N4O2ZnNa: 1023.5465 [M+Na]+;
found: 1023.5462.
short silica gel column chromatography and recrystallization (CH2Cl2/
MeOH) to provide compound 10.
A
2,8,12,18-tetrayl]tetraprop-2-enecarboxylic acid (13): Porphyrin tetraethyl
ester 6 (10.8 mg, 0.01 mmol) was dissolved in THF (1 mL). Then, ethanol
(1 mL) and aqueous NaOH (0.5 mL, 2m, 100 equiv) were added. The so-
lution was stirred under a N2 atmosphere at 708C (oil bath) for 20 h. The
solvent was removed in vacuo, and the residue was dissolved in water
(50 mL). The aqueous solution was extracted with CH2Cl2 (”2) to get rid
of the unreacted ester. The tetraacid was precipitated by the slow addi-
tion of aqueous 1m HCl to the aqueous solution. The precipitate was fil-
tered and washed thoroughly with water and CH2Cl2 to give product 13
(98%) as a dark-brown powder. 1H NMR (600 MHz, [D5]pyridine): d=
À1.95 (s, 2H; NH), 1.63 (s, 36H; tBu), 7.71–7.74 (d, 4H, J=15.9 Hz;
double bond), 8.15 (s, 2H; ArH), 8.51 (s, 4H; ArH), 9.76 (s, 4H; b-H),
9.94–9.97 (d, 4H, J=15.5 Hz; double bond), 11.16 ppm (s, 2H; meso-H);
MALDI-TOF-MS: m/z: calcd for C60H62N4O8 966.46 [M]+; found: 963;
UV/Vis (THF): lmax (e)=457 (1.7”105), 541 (1.8”104), 579 (7.8”103),
619 (6.8”103), 676 nm (tail, 2.3”103 mÀ1 cmÀ1).
5,10,15-Tris(3,5-di-tert-butylphenyl)-2,18-bis(3-oxooctyl)porphyrin
(9):
1H NMR (600 MHz, CDCl3): d=À2.85 (s, 2H; NH), 0.86 (t, J=6.4 Hz,
6H; Pen), 1.25–1.33 (m, 8H; Pen), 1.52 (s, 18H; tBu), 1.57 (s, 36H; tBu),
1.65–1.69 (m, 4H; Pen), 2.57 (t, J=7.3 Hz, 4H), 3.48 (t, J=7.8 Hz, 4H),
4.44 (t, J=7.8 Hz, 4H), 7.79 (s, 1H; ArH), 7.82 (s, 2H; ArH), 8.07 (s,
2H; ArH), 8.09 (s, 4H; ArH), 8.71 (s, 2H; b-H), 8.89 (s, 4H; b-H),
10.18 ppm (s, 1H; meso); HRMS(EIS):
m/z: calcd for C78H102N4O2:
1149.7895 [M+Na]+; found: 1149.7840.
Methyl (2E,4E)-5-[5,10,15-tris(3,5-di-tert-butylphenyl)porphyrin-2-yl]pen-
1
ta-2,4-dienoate (10): H NMR (600 MHz, CDCl3): d=À2.70 (s, 2H; NH),
1.50 (s, 18H; tBu), 1.54 (s, 18H; tBu), 1.56 (s, 18H; tBu), 3.88 (s, 3H;
OCH3), 6.25 (d, J=15.1 Hz, 1H), 7.60 (dd, J=15.6, 11.5 Hz, 1H), 7.78 (t,
J=1.9 Hz, 1H; Ar-para-H), 7.81 (t, J=1.8 Hz, 1H; Ar-para-H), 7.84 (t,
J=1.8 Hz, 1H; Ar-para-H), 7.97 (dd, J=15.1, 11.9 Hz, 1H), 8.04 (d, J=
1.9 Hz, 2H; Ar-ortho-H), 8.09 (d, J=1.8 Hz, 2H; Ar-ortho-H), 8.11 (d,
J=1.9 Hz, 2H; Ar-ortho-H), 8.64 (d, J=14.6 Hz, 1H), 8.86 (d, J=4.6 Hz,
1H; b-H), 8.90 (d, J=4.6 Hz, 2H; b-H), 8.92 (d, J=4.6 Hz, 1H; b-H),
9.06 (d, J=4.6 Hz, 1H; b-H), 9.18 (s, 1H; b-H), 9.37 (d, J=4.1 Hz, 1H;
b-H), 10.28 ppm (s, 1H; meso); UV/Vis (CH2Cl2): lmax (e)=304.0 (2.67”
104), 436.0 (1.85”105), 524.5 (2.08”104), 563.5 (1.21”104), 599.5 (7.99”
Acknowledgement
This work was partly supported by a Grant-in-Aid for Scientific Research
(no. 18685013) from MEXT. H.S. acknowledges the Asahi Glass Founda-
tion and the Ogasawara Science Foundation for financial support. J.C.
thanks the JSPS for a postdoctoral fellowship.
103), 655.5 nm (3.00”103 mÀ1 cmÀ1); fluorescence (CH2Cl2): lex
=
435.5 nm; lem =659, 726 nm; HRMS(ESI): m/z: calcd for C68H81N4O2:
985.6354 [M+H]+; found: 985.6382.
[1] a) M. D. G. H. Vicente in The PorphyrinHadnbook, Vol. 1
(Eds:
Methyl (3Z)-5-[5,10,15-Tris(3,5-di-tert-butylphenyl)porphyrin-2-yl]pent-3-
enoate (11): 1H NMR (600 MHz, CDCl3): d=À2.87 (s, 2H; NH), 1.50 (s,
18H; tBu), 1.55 (s, 36H; tBu), 3.60 (d, J=7.3 Hz, 2H), 3.75 (s, 3H;
OCH3), 4.93 (d, J=6.9 Hz, 2H), 6.02 (dtt, J=10.6, 7.3, 1.8 Hz, 1H), 6.52
(dtt, J=10.6, 7.3, 1.9 Hz, 1H), 7.78 (t, J=1.8 Hz, 1H; Ar-para-H), 7.79–
7.81 (m, 2H; Ar-para-H), 8.06 (d, J=1.8 Hz, 2H; Ar-ortho-H), 8.09 (d,
J=1.8 Hz, 2H; Ar-ortho-H), 8.10 (d, J=1.9 Hz, 2H; Ar-ortho-H), 8.75 (s,
1H; b-H), 8.90 (m, 3H; b-H), 8.94 (d, J=4.6 Hz, 1H; b-H), 9.04 (d, J=
4.6 Hz, 1H; b-H), 9.32 (d, J=4.6 Hz; b-H), 10.15 ppm (s, 1H; meso);
K. M. Kadish, K. M. Smith, R. Guilard), Academic Press, New
York, 2000, p. 149; b) L. Jaquinod in The PorphyrinHadnbook,
Vol. 1 (Eds: K. M. Kadish, K. M. Smith, R. Guilard), Academic
Press, New York, 2000, p. 201.
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DiMagno, V. S.-Y. Lin, M. J. Therien, J. Am. Chem. Soc. 1993, 115,
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HRMS(EIS):
987.6501.
m/z: calcd for C68H83N4O2: 987.6511 [M+H]+; found:
Dimethyl
(2E,2’E,4E,4’E)-5,5’-[5,10,15-tris(3,5-di-tert-butylphenyl)por-
phyrin-2,18-yl]dipenta-2,4-dienoate (12): 1H NMR (600 MHz, CDCl3):
d=À2.49 (s, 2H; NH), 1.50 (s, 18H; tBu), 1.56 (s, 36H; tBu), 3.90 (s, 6H;
OCH3), 6.27 (d, J=15.1 Hz, 2H), 7.61 (dd, J=15.1, 11.0 Hz, 2H), 7.78
(dd, J=1.9, 1.8 Hz, 1H; Ar-para-H), 7.85 (dd, J=1.8, 1.4 Hz, 2H; Ar-
para-H), 8.02 (d, J=1.4 Hz, 2H; Ar-ortho-H), 8.03 (dd, J=15.1, 11.5 Hz,
2H), 8.09 (d, J=1.9 Hz, 4H; Ar-ortho-H), 8.68 (d, J=15.6 Hz, 2H), 8.84
(d, J=4.6 Hz, 2H; b-H), 8.86 (d, J=4.6 Hz, 2H; b-H)), 9.18 (s, 2H; b-
H), 10.31 ppm (s, 1H; meso); UV/Vis (CH2Cl2): lmax (e)=302.5 (3.34”
104), 459.5 (1.53”105), 542.5 (1.88”104), 576.5 (8.17”103), 613.5 (7.34”
103), 674.0 nm (2.08”103 mÀ1 cmÀ1); fluorescence (CH2Cl2): lex =459;
lem =677, 746 nm; HRMS(ESI): m/z: calcd for C74H87N4O4: 1095.6722
[M+H]+; found: 1095.6749.
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G
G
CDCl3): d=1.51–1.57 (m, 54H; CH3 in tBu), 3.89 (s, 6H; OCH3), 6.24–
6.27 (d, J=15.1 Hz, 2H; double bond), 7.58–7.61 (dd, J=15.1 Hz, 2H;
double bond), 7.78 (s, 1H; Ar-para-H), 7.85 (s, 2H; Ar-para-H), 8.01–
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8.96 (m, 4H; b-H), 9.27 (s, 2H; porphyrin b-H), 10.38 ppm (s, 1H; por-
phyrin meso-H); MS(MALDI-TOF) m/z: calcd for C74H84N4O4Zn:
1156.58 [M]+; found: 1151.
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Received: December 8, 2007
Published online: March 25, 2008
4262
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