A novel method for the synthesis of regiospecifically sulfonated porphyrin monomers and dimers

Article abstract of DOI:10.1016/S0040-4020(03)00541-6

A novel method has been developed to regiospecifically synthesize water-soluble sulfonated porphyrin monomers tetrakis(4′-sulfonatophenyl)porphyrin, tetrakis(3′-sulfonatophenyl)porphyrin, tetrakis(2′-sulfonatophenyl)porphyrin, tetrakis(2′,5′-dimethyl-4′-sulfonatophenyl)porphyrin, the dimers of 1,2-bis[5,10,15-tri(4′-sulfonatophenyl)porphyrinyl]benzene and 1,2-bis[5,10,15-tri(2′,5′-dimethyl-4′-sulfonatophenyl) porphyrinyl]benzene in high yields through introduction of the trimethylsilyl group on the phenyl rings and reaction with trimethylsilyl chlorosulfonate in CCl₄ solvent.

Full text of DOI:10.1016/S0040-4020(03)00541-6

Tetrahedron 59 (2003) 3593–3601
A novel method for the synthesis of regiospecifically sulfonated
porphyrin monomers and dimers
a
Bao-Hui Yea,b and Yosinori Naruta
,
,
*
*
aInstitute for Fundamental Research of Organic Chemistry, Kyushu University, Higashi-Ku, Fukuoka 812-8581, Japan
bSchool of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, People’s Republic of China
Received 19 December 2002; revised 17 March 2003; accepted 28 March 2003
Abstract—A novel method has been0 developed to regiospecifically synthesize water-soluble sulfonated porphyrin monomers tet0rakis(40-
sulfonatophenyl)porphyrin, tetrakis(3 -sulfonatophenyl)porphyrin, tetrakis(20-sulfonatophenyl)porphyrin, tetrakis(20,50-dimet0hyl-4 -sulfon-
atophenyl)porphyrin, the dimers of 1,2-bis[5,10,15-tri(40-sulfonatophenyl)porphyrinyl]benzene and 1,2-bis[5,10,15-tri(20,5 -dimethyl-40-
sulfonatophenyl)porphyrinyl]benzene in high yields through introduction of the trimethylsilyl group on the phenyl rings and reaction with
trimethylsilyl chlorosulfonate in CCl4 solvent. q 2003 Elsevier Science Ltd. All rights reserved.
1. Introduction
isolated from the reaction medium because they are
insoluble in water but soluble in most of organic solvents.
The chlorosulfonyl intermediate is conveniently converted
into the corresponding sulfonic acids, sulfonate ethers, and
sulfonamides. However, this method is only employed to
sulfonate the para position of the phenyl rings or meta
position of the para-substituent phenyl rings. Furthermore,
they are unsuitable to sulfonate phenylene-bridged poly-
porphyrin due to the problems of sulfonation in indefinite
site and tedious chromatographic separation. On the other
hand, the trimethylsilylbenzene can react with the sulfona-
tion reagent, ClSO3SiMe3, to produce the corresponding
sulfonated benzene in quantitative yield.23 Herein, we report
a novel method to synthesize regiospecific water-soluble
sulfonated porphyrins in high yields through introduction of
the trimethylsilyl group on the phenyl rings and successive
reaction with trimethylsilyl chlorosulfonate. In addition, we
further demonstrated its application to the synthesis of
water-soluble sulfonated bisporphyrins. To the best of our
knowledge, these are the first examples of the water-soluble
sulfonated bisporphyrins.
Sulfonated metalloporphyrins are known to be typical
water-soluble ones and have been well investigated,1
which show applications not only for their anti-HIV
activities2 and tumor localizing properties in photodynamic
therapy3,4 or as contrast-enhancing agent in magnetic
resonance imaging,5 but also for their catalytic activity as
ligninase,6 chloroperoxidase7 and peroxidase models in
biomimetic catalysts for the oxidation of pollutants.8 In
addition, sulfonated porphyrins have also been widely
applied in analytical and supramolecular chemistry.9–14
The PdII complexes of sulfonated porphyrins have been
used to determine O2 levels in biological systems by
phosphorescence quenching12 and H(b-Br8-TSPP) [TSPP¼
tetrakis(4-sulfonatophenyl)porphyrin] to determine the
lithium ion in sea water and human serum.13,14
Sulfonation of phenyl rings in porphyrin is generally carried
out with concentrated sulfuric acid.15–21 The substitution
reaction usually occurs at the para position of the phenyl
rings. The yields of such reaction are usually not good and
the purification procedures are tedious and time-consuming.
A convenient and efficient method is therefore desired for
the synthesis of water-soluble sulfonated porphyrins.
Recently, chlorosulfonic acid was employed to prepare
sulfonated porphyrin.22 The major advantage is that the
initially formed chlorosulfonyl compounds are very easily
2. Results and discussion
The syntheses of tetrakis(p-sulfonatophenyl)porphyrin have
been well investigated.1 However, meta- and ortho-
sulfonatophenyl porphyrins were not well-documented
because the direct sulfonation reaction generally occurs at
the para position of their phenyl rings.15–21 This can be
overcome by introducing of a trimethylsilyl group to a
definite position, which reacts with trimethylsilyl
chlorosulfonate and can be converted to the sulfonate
quantitatively.23
Keywords: sulfonation; regiospecific; water-soluble porphyrin;
bisporphyrin; trimethylsilyl chlorosulfonate.
*
Corresponding authors. Address: School of Chemistry and Chemical
Engineering, Sun Yat-Sen University, Guangzhou 510275, People’s
Republic of China. Fax: þ86-20-84112245; e-mail: cesybh@zsu.edu.cn
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00541-6

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B.-H. Ye, Y. Naruta / Tetrahedron 59 (2003) 3593–3601
Scheme 1. Synthesis of 3a, 3b and 3d.
2.1. Synthesis of monomer porphyrins
The synthesis of trimethylsilylbenzaldehydes is outlined in
Scheme 1. Reaction of 1,4-dibromobenzene (1a) with
an equivalent of n-BuLi in Et2O at 2788C gave the mono-
lithiated intermediate, which further reacted with chloro-
trimethylsilane affording the corresponding 1-bromo-4-
(trimethylsilyl)benzene (2a) in 88% yield.24 4-Trimethyl-
silylbenzaldehyde (3a) was obtained in 75% by treatment of
2a with 1 equiv. n-BuLi in Et2O at room temperature in the
presence of dry DMF followed by hydrolysis of the
Scheme 2. Synthesis of 3c.
Scheme 3. Synthesis of sulfonated porphyrins.

B.-H. Ye, Y. Naruta / Tetrahedron 59 (2003) 3593–3601
3595
Scheme 4. Synthesis of sulfonated porphyrin dimers.
intermediate with aqueous HCl. The other trimethylsilyl-
benzaldehydes, 3b and 3d, were also synthesized by the
similar procedures in 60% yield based on 1b and 1d.
lithiation/phosphorylation of 1,2-dibromobenzene had
been reported.27 Trimethylsilylphenylporphyrins (4) have
been synthesized by Lindsey’s method25,26 and purified on
Al2O3 and silica gel columns in 40–48% yields. The
compounds were identified by elemental analysis, NMR and
ESI-MS spectra.
2-Trimethylsilylbenzaldehyde (3c) was prepared in 68%
yield by reaction of protected 2-bromobenzaldehyde with an
equivalent of n-BuLi in the presence of chlorotrimethyl-
silane, and then deprotection by trifluoroacetic acid
(Scheme 2). We had also tried in vain to prepare 3c by a
similar procedure as that for 3a. Only a trace amount of
1-bromo-(2-trimethylsilyl)benzene was obtained in the
reaction of 1,2-dibromobenzene with 1 equiv. n-BuLi and
then with chlorotrimethylsilane at 21308C, though
The syntheses of sulfonated porphyrins are shown in
Scheme 3. First, the sulfonation reaction at the para positio0n
of the phenyl rings of 4a was performed. Tetrakis(4 -
sulfonatophenyl)porphyrin (5a) was smoothly synthesized
through sulfonation of 4a with ClSO3SiMe3 in refluxing
CCl4 solution for 4 h and then hydrolysis of the intermediate

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B.-H. Ye, Y. Naruta / Tetrahedron 59 (2003) 3593–3601
Figure 1. Comparison of experimental ESI-MS of 9a (solid line) and calculated for C100H103N8Si6 (bar).
with aqueous NaOH.23 The reaction was monitored by
NMR spectroscopy and terminated when the peak of
trimethylsilyl had disappeared. The product was purified
by dialysis with cellulose dialysis membranes and
confirmed by NMR and ESI-MS spectra. In the course of
the synthesis of water-soluble sulfonated porphyrin, the
purification procedures are tedious and time-consuming
though a few methods, including a low-pressure reverse-
solvent made the reaction time shortened to 2 days under
refluxing condition to afford 5c in 85% yield.
2.2. Synthesis of porphyrin dimers
Although several 1,2-phenylene-bridged cofacial porphyrin
dimers have been synthesized,33 – 36 the cofacial
porphyrin dimer bearing trimethylsilyl groups have not
been reported. In order to synthesize the water-soluble
sulfonate porphyrins, the trimethylsilyl-substituted
porphyrin dimers linked by an o-phenylene bridge were
synthesized by the stepwise method37 outlined in Scheme 4.
phase silica gel column,19 a Sephadex G-10 column,28
a
celite column,29 and recrystallization15,30,31 have been
developed. The dialysis method is convenient and easily
controlled, but is dependent on the molecular weight.20,32 In
our case, the sulfonation reaction proceeded to completion
and produced only inorganic salt as a by-product. Therefore,
the dialysis method was the choice for 0 purification.
Furthermore, the sulfonation of tetrakis(20,5 -dimethyl-40-
trimethylsilyphenyl)porphyrin (4d), which bears two
methyl groups on each phenyl ring, was also successful
under these reaction conditions. In the mean time, we found
that the sulfonation reaction did not proceed completely
when CH2Cl2 was used in place of CCl4. A mixture of
mono-, di-, tri-, and tetra-substituted porphyrins was
produced. This suggests that the reaction temperature
greatly affect this electrophilic substitution.
The porphyrin 6a was synthesized by Lindsey’s method.25
Cross-condensation of the methyl 2-formylbenzoate and 3a
(3 equiv.) and pyrrole (4 equiv.) in the presence of BF3·Et2O
as catalyst in CHCl3 followed by oxidation with DDQ gave
the asymmetric porphyrin 6a in 18%. In the mean time, the
symmetric porphyrin 4a was obtained as the by-product in
about 12% yield. Subsequent reduction of 6a by LiAlH4 in
THF at room temperature afforded 7a in 88% yield. Further
oxidation of 7a by active MnO2 afforded formylphenyl-
porphyrin 8a in 95% yield. The porphyrin dimer 9a was
synthesized by condensation of 8a (1 equiv.) and 4a
(11 equiv.) and pyrrole (12 equiv.) in the presence of
BF3·Et2O as catalyst in CHCl3. The subsequent oxidation
with DDQ and separation by silica gel flash column
chromatography gave the porphyrin dimer 9a in 23%
yield based on 8a. The symmetric porphyrin 5a was
obtained in 15% yield. The product was identified by
NMR and ESI-MS spectra. The ESI-MS spectrum gave a
very clear and strong isotopic cluster peaks centered at
m/z¼1584.8 for 9a (Fig. 1). The mass spectrum of these
clusters and the intensity ratio of the different isotope peaks
are in excellent agreement with the calculated isotope
pattern for the excepted molecules, [MþH]þ. The porphyrin
dimer 9b was also synthesized in a similar way as that of 9a
and identified by NMR and ESI-MS spectra.
Secondly, the sulfonation for meta-substituted porphyrin
was also0 successfully carried out. Indeed, treatment of
tetrakis(3 -trimethylsilylphenyl)porphyrin (4b) with ClSO3-
SiMe3 afforded the corresponding tetrakis(30-sulfonato-
phenyl)porphyrin (5b) in a high yield of 90%. We had
also tried to exploit0this method to synthesize the previously
unknown tetrakis(2 -sulfonatophenyl)porphyrin (5c). Thus,
treatment of tetrakis(20-trimethylsilylphenyl)porphyrin (4c)
with ClSO3SiMe3 under the same reaction conditions as
those of 4a gave only a trace amount of product 5c in 4 h.
After extending the reaction to 4 days, 5c was obtained in
82% yield. As compared with the preparation of the 4a, 4b
and 4d, 4c needed longer reaction time, which is likely due
to the steric hindrance of the bulky ortho-substituent. In
order to shorten the reaction time, increase in the reaction
temperature with 1,1,2,2-tetrachloroethane (TCE) as a
The sulfonated porphyrin dimers, 10a and 10b, were
obtained in 96 and 90% yield, respectively, by sulfonation

B.-H. Ye, Y. Naruta / Tetrahedron 59 (2003) 3593–3601
3597
Table 1. Sulfonation of porphyrins
distilled water for 4 h, and then one end was sealed with a
clump. The porphyrin sample was dissolved in a minimum
amount of distilled water, and the resulting solution was
transferred into the tubing; the other end of the tubing was
then closed with string. The dialysis tubing was hung on the
wall of beaker containing distilled water (1.8 L). The water
outside the dialysis tubes was replaced by distilled water
and the dialysis was continued for 4 days. After which the
solution in the tubing was evaporated to dryness.
Compound
Solvent
Time
Yield (%)a
5a
5b
5c
5d
10a
10b
CCl4
CCl4
TCE
CCl4
CCl4
CCl4
4 h
4 h
2 days
4 h
5 h
95
90
85
90
96
90
5 h
a
Isolated yields based on porphyrins.
NMR spectra were recorded on either a JEOL JMX-GX400
or a Varian INOVA 500 spectrometer using solvent as an
internal standard. Chemical shifts are reported as parts per
million (ppm) with respect to tetramethylsilane (TMS). IR
spectra were recorded on a Bruker VECTOR 22 spec-
trometer. A Shimadzu UV 2500-PC spectrophotometer was
used for measuring electronic absorption spectra at room
temperature. Electrospray ionization mass spectra (ESI-MS)
were obtained on a Perkin–Elmer Sciex API 300 spec-
trometer. Elemental analyses (C, H and N) were performed
on an Elementar Vario EL Elemental analyzer.
of 9a and 9b with ClSO3SiMe3 in refluxing CCl4 for 5 h
followed by hydrolysis of the intermediate with aqueous
NaOH (Table 1). Compounds 10a and 10b were also
successfully purified by dialysis with cellulose dialysis
membranes.
3. Conclusion
In conclusion, we have developed a novel method for the
regiospecific synthesis of water-soluble sulfonated
porphyrin monomers and 1,2-phenylene-bridged dimers in
high yields through the introduction of the trimethylsilyl
group on the phenyl rings and reaction with ClSO3SiMe3.
This method can also be applied to synthesize mono-, di-
and tri-substituted sulfonated porphyrins in a regiospecific
manner.
4.1.1. 1-Bromo-4-(trimethylsilyl)benzene (2a).24 To a
stirring solution of 1,4-dibromobenzene (9.44 g, 40 mmol)
in diethyl ether (80 mL) was added n-BuLi (26.7 mL,
40 mmol, 1.5 M in hexane) over 1 h under nitrogen
atmosphere at 2788C. The solution was stirred at this
temperature until the reaction was completed (monitored by
TLC, about 30 min). Then, chlorotrimethylsilane (5.33 mL,
42 mmol) was added over about 10 min. The solution was
allowed to warm to room temperature and stirred until the
reaction completed (monitored by TLC, about 1.5 h). Water
(15 mL) was added to the above solution. The organic layer
was separated and washed with brine, then dried over
magnesium sulfate. Filtration and removal of the solvent
gave a colorless oil, which was purified by column
chromatography (silica gel, hexane) and dried in vacuo
(yield 8.1 g, 88%, colorless oil). dH (400 MHz, CDCl3) 7.48
(2H, d, J¼8.3 Hz, ph–H2), 7.37 (2H, d, J¼8.3 Hz, ph–H3),
0.26 (9H, s, Me); dC (400 MHz, CDCl3) 140.8, 133.5 129.7,
128.3, 21.4.
4. Experimental
4.1. General
All reagents and solvent were of the commercial reagent
grade and were used without further purification unless
otherwise noted. Chlorotrimethylsilane was distilled under a
nitrogen atmosphere prior to use. N,N-dimethylformamide
(DMF) was treated with BaO overnight, then distilled from
˚
calcium hydride under reduced pressure and stored over 4 A
molecular sieves. Pyrrole was purchased from Tokyo Kasei,
distilled under reduced pressure and stored in sealed
ampoules. Active MnO2 was prepared by Attenburrow’s
method.38 Reagent grade diethyl ether was treated with
CaCl2, then distilled under nitrogen from sodium benzo-
phenone ketyl. CH2Cl2 was treated successively with
H2SO4 and K2CO3, then distilled from CaH2. THF was
treated with KOH, then distilled from sodium benzo-
phenone ketyl. Reagent grade chloroform (for the synthesis
of porphyrin ligands) was fractionally distilled from K2CO3
before use. Carbon tetrachloride was treated with standard
4.1.2. 1-Bromo-3-(trimethylsilyl)benzene (2b).24 The
same procedure as for 2a afforded 2b as a colorless oil in
85% yield. dH (400 MHz, CDCl3) 7.54 (1H, s, ph–H2), 7.39
(1H, d, J¼7.6 Hz, ph–H4), 7.34 (1H, d, J¼7.3 Hz, ph–H6),
7.14 (1H, t, ph–H5), 0.195 (9H, s, Me); dC (400 MHz,
CDCl3) 143.7, 135.9, 131.8, 131.6, 129.5, 122.9, 21.3.
4.1.3. 2-Trimethylsilylbenzaldehyde diethyl acetal (2c).39
The procedure is similar to the synthesis of 2a, using
2-bromobenzaldehyde diethyl acetal in place of 1,4-
dibromobenzene and the reaction was carried out at room
temperature, affording 2c as a colorless oil in 75% yield. dH
(400 MHz, CDCl3) 7.71 (1H, d, J¼7.8 Hz, ph–H3), 7.58
(1H, d, J¼7.8 Hz, ph–H6), 7.37 (1H, t, ph–H4), 7.29 (1H, t,
ph–H5), 5.61 (1H, s, phCH(OEt)2), 3.60–3.66 (2H, m,
OCH2Me), 3.45–3.51 (2H, m, OCH2Me), 1.23 (6H, t,
OCH2Me), 0.370 (9H, s, SiMe3).
˚
method and distilled from P2O5, then stored over 4 A
molecular sieves. For dialysis, cellulose membrane
(Viskase, 27/32, fractionating MW range: 12000–14000)
was used. Thin layer chromatography (TLC) was performed
on Merck silica gel 60 pre-coated aluminum sheets and
visualized using visible or UV light (254 and 365 nm).
Column chromatography was carried out under a positive
nitrogen pressure using Merck silica gel (200–400 mesh) or
neutral Al2O3.
4.1.4. 1-Bromo-2,5-dimethyl-4-(trimethylsilyl)benzene
(2d).24 The same procedure as for 2a afforded 2d as a
colorless oil in 86% yield. dH (400 MHz, CDCl3) 7.34 (1H,
Dialysis was carried out in a 2-L beaker. A 12£2.1B cm
piece of cellulose dialysis membrane tubes were rinsed with

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B.-H. Ye, Y. Naruta / Tetrahedron 59 (2003) 3593–3601
s, ph–H6), 7.27 (1H, s, ph–H3), 2.39 (3H, s, ph–Me), 2.36
(3H, s, ph–Me), 0.31 (9H, s, SiMe3).
monitored by TLC. At the end of 40 min, 2,3-dichloro-
5,6-dicycano-1,4-benoquinine (DDQ) (4.08 g, 18 mmol)
dissolved in benzene (100 mL) was added and the solution
was further stirred at room temperature for 1 h. After the
elimination of the insoluble solid by filtration, the filtrate
was concentrated and loaded on Al2O3 (200 g) column, the
crude products were eluted by CHCl3. The porphyrin was
further purified on silica gel column (chloroform–hexane,
1:1), then concentrated and dried. Yield, 48%. [Found: C,
74.31; H, 6.60; N, 6.03. C56H62N4Si4 requires C, 74.53; H,
6.81; N, 6.21%]; nmax (KBr) 3580–3498, 3240–3180, 1595,
1472, 1400, 1248, 1108, 966, 879, 845, 799, 756, 728, 708,
624 cm21; dH (400 MHz, CDCl3) 8.75 (8H, s, pyrrole b-H),
8.09 (8H, d, J¼7.32 Hz, ph–H2), 7.79 (8H, d, J¼7.32 Hz,
ph–H3), 0.42 (36H, s, Me) and 22.87 (2H, br, N–H); dC
(100 MHz, CDCl3) 147.0, 142.5, 138.5, 134.1, 131.6, 131.0,
120.2, 20.8. ESI-MS: found 903 (100%). C56H63N4Si4
[MþH]þ requires 903. UV–vis: lmax/nm (CH2Cl2): 419,
480, 516, 552, 590, 646.
4.1.5. 4-Trimethylsilylbenzaldehyde (3a). To a solution of
2a (4.56 g, 20 mmol) in diethyl ether (30 mL) was added a
solution of n-BuLi (13.40 mL, 20 mmol, 1.5 M in hexane)
by a syringe over a period of 30 min under nitrogen at 08C.
The solution was stirred at this temperature for further a
30 min, then stirred at room temperature for 1.5 h. A
solution of DMF (2.46 mL, 32 mmol) in diethyl ether
(15 mL) was added to the solution, and the mixture solution
was stirred overnight, then treated with 10% hydrochloric
acid. The organic layer was separated and the aqueous layer
was extracted with chloroform (2£40 mL). The combined
organic layer was washed with NaHCO3 and brine, then
dried over MgSO4. After filtration and removal of the
solvent, the slightly yellowish oil was chromatographed on
a silica gel column eluting with hexane–acetone (9:1, v/v)
to afford the title compound as a colorless oil in 75% yield
(2.7 g). dH (400 MHz, CDCl3) 10.02 (1H, s, CHO), 7.83
(2H, d, J¼8.3 Hz, ph–H2), 7.69 (2H, d, J¼8.3 Hz, ph–H3),
0.30 (9H, s, Me); dC (100 MHz, CDCl3) 192.6, 149.2, 136.4,
133.8, 128.6, 21.4.
4.1.10. 5,10,15,20-Tetra(30-trimethylsilylphenyl)por-
phyrin (4b). The same procedure as for 4a afforded 4b as
a purple solid in 45% yield. [Found: C, 74.42; H, 6.55; N,
6.14. C56H62N4Si4 requires C, 74.53; H, 6.81; N, 6.21%];
4.1.6. 3-Trimethylsilylbenzaldehyde (3b). The same
procedure as for 3a afforded 3b as a colorless oil in 70%
yield. dH (400 MHz, CDCl3) 9.93 (1H, s, CHO), 7.93 (1H, s,
ph–H2), 7.74 (1H, d, J¼7.8 Hz, ph–H6), 7.67 (1H, d,
J¼7.3 Hz, ph–H4), 7.40 (1H, t, ph–H5), 0.216 (9H, s, Me);
dC (100 MHz, CDCl3) 192.6, 141.6, 139.2, 135.4, 134.5,
130.0, 128.2, 21.4.
nmax (KBr) 3540–3488, 1637, 1401, 1248, 1116, 974, 841,
799, 752, 621 cm21; dH (400 MHz, CDCl3) 8.87 (8H, s,
pyrrole b-H), 8.37 (4H, d, J¼7.8 Hz, ph–H6), 8.21 (4H, s,
ph–H2), 7.92 (4H, d, J¼7.3 Hz, ph–H4), 7.74 (4H, t,
ph–H5), 0.41 (36H, s, Me) and 22.71 (2H, br, N–H); dC
(100 MHz, CDCl3) 147.1, 141.5, 139.5, 138.7, 135.0, 132.5,
131.2, 126.0, 120.5, 20.9. ESI-MS: found 903 (100%).
C56H63N4Si4 [MþH]þ requires 903.
4.1.7. 2-Trimethylsilylbenzaldehyde (3c). The 2c (2.52 g,
1 mmol) was dissolved in a CH2Cl2 (40 mL). Trifluoro-
acetic acid (25 mL) and water (15 mL) were added to the
solution. The mixture was stirred at room temperature for
6 h. The organic layer was separated and washed succes-
sively with water, aqueous NaHCO3, brine, then dried over
Na2SO4. After filtration and removal of the solvent, the
slightly yellowish oil was chromatographed on silica gel
column eluting with hexane–benzene (2:1, v/v) to afford the
title compound as a colorless oil in 90% yield (1.6 g). dH
(400 MHz, CDCl3) 10.17 (1H, s, CHO), 7.89 (1H, d, J¼
7.8 Hz, ph–H6), 7.72 (1H, d, J¼7.8 Hz, ph–H3), 7.53–7.58
(2H, m, ph–H4 and ph–H5), 0.36 (9H, s, Me); dC (100 MHz,
CDCl3) 193.5, 142.7, 141.0, 135.6, 133.0, 132.5, 129.3, 0.04.
4.1.11. 5,10,15,20-Tetra(20-trimethylsilylphenyl)por-
phyrin (4c). The same procedure as for 4a afforded 4c as
a purple solid in 42% yield. [Found: C, 74.29; H, 6.64; N,
6.03. C56H62N4Si4 requires C, 74.53; H, 6.81; N, 6.21%];
n
max (KBr) 3480–3450, 1637, 1401, 1248, 1122, 966, 836,
802, 746, 622 cm21; dH (400 MHz, CDCl3) 8.57 (8H, s,
pyrrole b-H), 7.97 (4H, d, J¼7.2 Hz, ph–H6), 7.92 (4H, d,
J¼7.6 Hz, ph–H3), 7.74 (4 h, t, ph–H4), 7.59 (4H, t,
ph–H5), 20.78 (36H, s, Me) and 22.67 (2H, br, N–H); dC
(125.7 MHz, CDCl3) 147.7, 143.3, 134.0, 133.8, 132.9,
131.1, 127.2, 126.3, 121.2, 20.2. ESI-MS: found 903
(100%). C56H63N4Si4 [MþH]þ requires 903.
4.1.12. 5,10,15,20-Tetra(20,50-dimethyl-30-trimethylsilyl-
phenyl)porphyrin (4d). The same procedure as for 4a
afforded 4d as a purple solid in 40% yield. [Found: C, 75.47;
H, 7.51; N, 5.36. C56H62N4Si4 requires C, 75.68; H, 7.74; N,
5.52%]; nmax (KBr) 3480–3458, 2953, 1597, 1560, 1472,
1401, 1249, 1227, 1187, 1071, 979, 938, 854, 834, 803, 761,
732, 696, 628, 472 cm21; dH (400 MHz, CDCl3) 8.68 (8H,
s, pyrrole b-H), 7.79–7.73 (4H, m, ph–H6), 7.63 (4H, s,
ph–H3), 2.63–2.60 (12H, q, ph–Me), 2.05–1.98 (12H, q,
ph–Me), 0.55 (36H, s, SiMe3) and 22.64 (2H, br, N–H); dC
(125.7 MHz, CDCl3) 147.2, 142.2, 141.0, 138.8, 138.2,
135.6, 135.2, 130.2, 118.8, 22.6, 20.8, 0.2. ESI-MS: found
1015 (100%). C64H79N4Si4 [MþH]þ requires 1015. UV–
vis (lmax/nm CH2Cl2): 370, 418, 478, 514, 548, 590, 644.
4.1.8. 2,5-Dimethyl-4-trimethylsilylbenzaldehyde (3d).
The same procedure as for 3a afforded 3d as a colorless
oil in 70% yield. dH (400 MHz, CDCl3) 10.24 (1H, s, CHO),
7.54 (1H, s, ph–H6), 7.32 (1H, s, ph–H3), 2.62 (3H, s,
ph–Me), 2.48 (3H, s, ph–Me), 0.34 (9H, s, SiMe3); dC
(100 MHz, CDCl3) 193.1, 146.2, 141.4, 137.8, 136.2, 134.2,
130.3, 22.3, 19.0, 20.4.
4.1.9. 5,10,15,20-Tetra(40-trimethylsilylphenyl)por-
phyrin (4a). This compound was synthesized by Lindsey’s
method.25 To a 1-L three-necked round-bottomed flask
containing CHCl3 (500 mL) were added 3a (20.0 mmol)
and pyrrole (1.34 g, 20.0 mmol). After the solution was
purged with nitrogen for 10 min, BF3·OEt2 (0.25 mL,
2 mmol) was added via a syringe. The mixture was stirred
at room temperature under nitrogen atmosphere and
4.1.13. Tetrasodium tetrakis(40-sulfonatophenyl)por-
phyrin (5a).15 To a CCl4 (20 mL) solution containing 4a

B.-H. Ye, Y. Naruta / Tetrahedron 59 (2003) 3593–3601
3599
(0.1 mmol) was added ClSO3SiMe3 (0.226 g, 1.2 mmol).
The mixture solution was refluxed under nitrogen atmos-
phere for 4 h. Upon cooling to room temperature, NaOH
solution (1N, 15 mL) was added to the above solution and
stirred for 0.5 h. The solution was separated to two layers.
The aqueous layer was washed with CHCl3 three times
(3£20 mL), concentrated to 5 mL and purified through
membrane for 4 days. The sulfonated porphyrin was
obtained by removing the water, then washed with acetone
and dried. Yield, 95%. [Found: C, 51.44; H, 2.40; N, 5.33.
C44H26N4O12S4Na4 requires C, 51.66; H, 2.54; N, 5.48%];
dH (400 MHz, DMSO-d6) 8.92 (8H, s, pyrrole b-H), 8.25
(8H, d, J¼7.58 Hz, ph–H3), 8.12 (8H, d, J¼7.58 Hz, ph–
H2), 22.84 (2H, br, N–H). ESI-MS: found 935 (100%).
[C44H26N4S4O12þ5H]þ requires 935.
4.1.14. Tetrasodium tetrakis(30-sulfonatophenyl)por-
phyrin (5b). The same procedure as for 5a afforded 5b as
a purple solid in 90% yield. [Found: C, 51.45; H, 2.30; N,
5.31. C44H26N4O12S4Na4 requires C, 51.66; H, 2.54; N,
5.48%]; dH (400 MHz, DMSO-d6) 8.84 (8H, s, pyrrole
b-H), 8.40 (4H, d, J¼7.8 Hz, ph–H6), 8.25, (4H, s, ph–H2),
8.10 (4H, d, J¼7.3 Hz, ph–H4), 7.82 (4H, t, ph–H5), 22.70
(2H, br, N–H). ESI-MS: found 935 (100%).
[C44H26N4S4O12þ5H]þ requires 935.
(2.67 g, 15.0 mmol), methyl 2-formylbenzoate (0.82 g,
5.0 mmol) and pyrrole (1.34 g, 20.0 mmol), respectively.
After the solution was purged with nitrogen for 10 min,
BF3·OEt2 (0.25 mL, 2 mmol) was added via a syringe. The
mixture was stirred at room temperature under nitrogen
atmosphere and monitored by TLC. At the end of the 40 min
reaction, DDQ (4.08 g, 18 mmol) dissolved in benzene
(100 mL) was added and the solution was further stirred at
room temperature for 1 h. After the elimination of the
insoluble solid by filtration, the filtrate was concentrated and
loaded on Al2O3 (200 g) column, the crude products were
eluted by CHCl3. The title porphyrin was purified on silica
gel column (chloroform–hexane, 1:1), then concentrated
and dried. Yield, 0.78 g, 18%. [Found: C, 74.10; H, 6.25; N,
6.08. C55H56N4O2Si3 requires C, 74.28; H, 6.35; N, 6.30%];
nmax (KBr) 3470–3410, 2954, 1733, 1637, 1596, 1472,
1400, 1249, 1107, 1084, 982, 967, 878, 839, 799, 761, 734,
696, 624, 532 cm21; dH (400 MHz, CDCl3) 8.73 (4H, d,
J¼7.3 Hz), 8.53 (2H, d, J¼4.6 Hz), 8.29 (2H, d, J¼5.2 Hz),
8.13–8.03 (8H, m), 7.80–7.72 (8H, m), 2.64 (3H, s, OMe),
0.42 (9H, s, SiMe3), 0.41 (18H, s, SiMe3), 22.78 (2H, br,
N–H); dC (125.7 MHz, CDCl3) 167.9, 142.6, 142.5, 139.5,
136.1, 134.2, 134.1, 131.6, 129.7, 128.3, 120.2, 118.9, 51.5,
20.8. ESI-MS: found 889 (100%). C55H57N4O2Si3
[MþH]þ requires 889.
4.1.15. Tetrasodium tetrakis(20-sulfonatophenyl)por-
phyrin (5c). The similar procedure as for 5a but using
TCE in place of CCl4 afforded 5c as a purple solid in 85%
yield. [Found: C, 51.51; H, 2.32; N, 5.30. C44H26N4O12S4-
Na4 requires C, 51.66; H, 2.54; N, 5.48%]; dH (400 MHz,
DMSO-d6) 8.84 (8H, br, pyrrole b-H), 8.20 (4H, br,
ph–H3), 8.04, (4H, d, ph–H6), 7.80–7.86 (8H, t, ph–H4
and ph–H5), 22.72 (2H, br, N–H). ESI-MS: found 935
(100%). [C44H26N4S4O12þ5H]þ requires 935.
4.1.16. Tetrasodium tetrakis(20,50-dimethyl-40-sulfonato-
phenyl)porphyrin (5d). The same procedure as for 5a
afforded 5d as a purple solid in 90% yield. [Found: C, 54.91;
H, 3.42; N, 4.78. C52H42N4O12S4Na4 requires C, 55.03; H,
3.70; N, 4.94%]; dH (400 MHz, DMSO-d6) 8.67 (8H, s,
pyrrole b-H), 8.04 (4H, s, ph–H3), 7.83–7.71 (4H, m,
ph–H6), 2.71 (12H, s, ph–Me), 2.01–1.88 (12H, m,
ph–Me), 22.78 (2H, br, N–H). ESI-MS: found 1047
(100%). [C52H42N4S4O12þ5H]þ requires 1047. UV–vis
(lmax/nm MeOH): 309, 413, 511, 543, 587, 643.
4.1.19. 5-(20-Methylbenzoate)-10,15,20-tri(200,500-
dimethyl-400-trimethylsilylphenyl) porphyrin (6b). The
same procedure as for 6a afforded 6b as a purple solid in
16% yield. [Found: C, 75.02; H, 6.95; N, 5.54.
C61H68N4O2Si3 requires C, 75.26; H, 7.04; N, 5.76%]; dH
(400 MHz, CDCl3) 8.67 (6H, s), 8.62–8.58 (2H, q), 8.39–
8.36 (1H, q), 8.12–8.07 (1H, m), 7.86–7.70 (5H, m), 7.65–
7.62 (3H, m), 2.79–2.80 (3H, m, OMe), 2.63–2.59 (9H, m,
ph–Me), 2.07–1.98 (9H, m, ph–Me), 0.54 (27H, s, SiMe3),
22.59 (2H, br, N–H). ESI-MS: found 973 (100%).
C61H69N4O2Si3 [MþH]þ requires 973.
4.1.20. 5-(20-Benzomethanol)-10,15,20-tri(400-trimethyl-
silylphenyl)porphyrin (7a). To a suspension of LiAlH4
(0.443 g, 12 mmol) in dry THF (40 mL) was slowly added a
solution of 6a (0.445 g, 0.5 mmol) dissolved in dry THF
(20 mL) at 08C. The mixture was stirred for 30 min at room
temperature under nitrogen atmosphere. After the reaction
was completed, methanol (10 mL) was added for quenching
at 08C. Removal of the solvent, the residue was dissolved in
CH2Cl2 (50 mL) and neutralized (pH¼5–7) by 1N HCl.
The organic layer was separated and washed with saturated
NaHCO3. The solvent was removed and the crude product
was purified on silica gel C-200 column (benzene), given
purple crystals. Yield, 0.37 g, 88%. [Found: C, 75.12; H,
6.28; N, 6.24. C54H56N4OSi3 requires C, 75.30; H, 6.55; N,
6.50%]; dH (400 MHz, CDCl3) 8.77 (4H, d, J¼4.9 Hz), 8.59
(2H, d, J¼3.4 Hz), 8.15–8.18 (8H, m), 7.99–7.73 (8H, m),
7.61–7.55 (2H, m), 4.26 (2H, d, J¼5.9 Hz, CH2OH), 0.44
(9H, s, SiMe3), 0.43 (18H, s, SiMe3), 22.80 (2H, br, N–H).
ESI-MS: found 861 (100%). C54H57N4OSi3 [MþH]þ
requires 861.
4.1.17. Methyl 2-formylbenzoate.39 To a solution of
K2CO3 (70.0 g) and 2-formylbenzoic acid (24.0 g,
0.16 mol) in acetone (500 mL) was added methyl iodide
(23.0 g, 0.16 mol) at room temperature. The mixture was
refluxed under nitrogen atmosphere for 4 h. After cooling to
room temperature, the mixture was filtrated and concen-
trated, then, the residue was extracted by CHCl3 and washed
by saturated Na2SO4 and NaCl. After removing the solvent,
the product was distilled under reduced pressure to give
19.0 g in 72.3% yield. dH (400 MHz, CDCl3) 10.62 (1H, s,
CHO), 7.99–7.93 (2H, m, ph–H), 7.67–7.65 (2H, m,
ph–H), 3.98 (3H, s, Me).
4.1.21. 5-(20-Benzomethanol)-10,15,20-tri(200,500-
dimethyl-400-trimethylsilylphenyl) porphyrin (7b). The
same procedure as for 7a afforded 7b as a purple solid in
86% yield. [Found: C, 75.98; H, 7.08; N, 5.78.
4.1.18. 5-(20-Methylbenzoate)-10,15,20-tri(400-trimethyl-
silylphenyl)porphyrin (6a). To a 1-L three-neck round-
bottomed flask containing CHCl3 (500 mL) were added 3a

3600
B.-H. Ye, Y. Naruta / Tetrahedron 59 (2003) 3593–3601
C60H68N4OSi3 requires C, 76.22; H, 7.25; N, 5.93%]; dH
(400 MHz, CDCl3) 8.59 (6H, s), 8.52 (2H, d, J¼4.8 Hz),
7.98–7.90 (1H, m), 7.84–7.70 (1H, m), 7.68–7.61 (5H, m),
7.53 (3H, s), 4.25 (2H, d, J¼5.9 Hz, CH2OH), 2.54–2.52
(9H, m, ph–Me), 1.96–1.86 (9H, m, ph–Me), 0.45 (27H, s,
SiMe3), 22.75 (2H, br, N–H). ESI-MS: found 945 (100%).
C60H69N4OSi3 [MþH]þ requires 945.
4.1.22. 5-(20-Benzoaldehyde)-10,15,20-tri(400-trimethyl-
silylphenyl)porphyrin (8a). To a solution of 7a (0.430 g,
0.5 mmol) in dry CH2Cl2 (100 mL) was added MnO2
(0.88 g, 10 mmol). The mixture was stirred at room
temperature for 3 h (monitored by TLC) under nitrogen
atmosphere. After the elimination of the insoluble MnO2 by
filtration, the filtrate was concentrated. The crude product
was purified on silica gel C-200 column (CH2Cl2), given
purple crystals. Yield, 0.41 g, 96%. [Found: C, 75.24; H,
6.178; N, 6.35. C54H54N4OSi3 requires C, 75.48; H, 6.33; N,
6.52%]; dH (400 MHz, CDCl3) 9.38 (1H, s, CHO), 8.77 (4H,
d, J¼4.6 Hz), 8.52 (2H, d, J¼4.9 Hz), 8.32–8.29 (2H, m),
8.16–8.09 (8H, m), 7.87–7.77 (8H, m), 0.418 (9H, s,
SiMe3), 0.412 (18H, s, SiMe3), 22.79 (2H, br, N–H). ESI-
MS: found 859 (100%). C54H55N4OSi3 [MþH]þ requires
859.
4.1.25. 1,2-Bis[5,10,15-tri(20,50-dimethyl-40-trimethyl-
silylphenyl)porphyrinyl]benzene (9b). The same
procedure as for 9a afforded 9b as a purple solid in 22%
yield. [Found: C, 76.61; H, 7.02; N, 6.15. C112H126N8Si6
requires C, 76.75; H, 7.25; N, 6.39%]; nmax (KBr) 3430–
3410, 3210, 2953, 1637, 1598, 1400, 1249, 975, 941, 854,
834, 801, 760, 730, 696, 628, 471 cm21; dH (400 MHz,
CDCl3) 9.25–9.21 (12H, m), 8.79–8.73 (4H, m), 8.32–8.28
(10H, m), 7.52–7.40 (6H, m), 2.56–2.37 (36H, m), 0.56–
0.54 (36H, m), 0.43–0.42 (18H, m) and 23.60 (4H, br).
ESI-MS: found 1752 (100%). C112H127N8Si6 [MþH]þ
requires 1752. UV–vis: lmax/nm (CH2Cl2): 408, 521, 596,
649.
4.1.26. Sodium 1,2-bis[5,10,15-tri(40-sulfonatophenyl)-
porphyrinyl]benzene (10a). To the CCl4 (20 mL) solution
containing 9a (0.158 g, 0.1 mmol) was added ClSO3SiMe3
(0.226 g, 1.2 mmol). The mixture solution was refluxed 5 h
under nitrogen atmosphere. After cooling to room tempera-
ture, NaOH (1N, 15 mL) was added to the above solution
and stirred for 0.5 h. A two layers solution was separated.
The aqueous layer was washed with CHCl3 three times
(3£20 mL), concentrated to 5 mL and purified through
membrane for 4 days. The sulfonated porphyrin was
obtained by removing the water, then washed with acetone
and dried. Yield, 96%. [Found: C, 55.58; H, 2.48; N, 6.14.
C82H48N8O18S6Na6 requires C, 55.84; H, 2.74; N, 6.35%];
dH (400 MHz, DMSO-d6) 9.69 (4H, br), 9.18 (2H, s), 8.69–
8.71 (14H, m), 8.38 (4H, br), 8.20–8.25 (12H, m), 8.19 (4H,
br), 8.06 (4H, t), 7.88 (4H, t), 23.72 (4H, br). ESI-MS:
found 816 (100%). [C82H48N8S6O18þ8H]2þ requires 816.
UV–vis: lmax/nm (MeOH): 309, 413, 511, 543, 587, 643.
4.1.23. 5-(20-Benzoaldehyde)-10,15,20-tri(200,500-
dimethyl-400-trimethylsilylphenyl) porphyrin (8b). The
same procedure as for 8a afforded 8b as a purple solid in
95% yield. [Found: C, 76.13; H, 6.89; N, 5.79.
C60H66N4OSi3 requires C, 76.38; H, 7.05; N, 5.94%]; dH
(400 MHz, CDCl3) 9.61–9.45 (1H, m, CHO), 8.73–8.71
(6H, m), 8.58–8.56 (2H, m), 8.42–8.39 (1H, m), 7.94–7.89
(1H, m), 779–7.73 (4H, m), 7.64 (4H, s), 2.63–2.61 (9H, m,
ph–Me), 2.04–1.98 (9H, m, ph–Me), 0.554 (27H, s,
SiMe3), 22.61 (2H, br, N–H). ESI-MS: found 943
(100%). C60H67N4OSi3 [MþH]þ requires 943.
4.1.27. Sodium 1,2-bis[5,10,15-tri(20,50-dimethyl-40-sul-
ponatophenyl)porphyrinyl] benzene (10b). The same
procedure as for 10a afforded 10b as a purple solid in
90% yield. [Found: C, 58.28; H, 3.48; N, 5.53. C94H72N8-
O18S6Na6 requires C, 58.44; H, 3.75; N, 5.80%]; dH
(400 MHz, DMSO-d6) 9.46 (8H, br), 8.92–8.95 (6H, m),
8.30–8.33 (8H, m), 7.93 (4H, br), 7.39–7.42 (6H, m), 2.76–
2.42 (18H, m), 1.87–1.32 (18H, m), 23.78 (4H, br). ESI-
MS: found 900 (100%). [C94H72N8S6O18þ8H]2þ requires
900. UV–vis: lmax/nm (MeOH): 307, 408, 520, 548, 594,
652.
4.1.24. 1,2-Bis[5,10,15-tri(40-trimethylsilylphenyl)por-
phyrinyl]benzene (9a). To a 300-mL three-neck round-
bottomed flask containing CHCl3 (150 mL) were added 8a
(0.429 g, 0.5 mmol), 3a (0.980 g, 5.5 mmol) and pyrrole
(0.420 g, 6.0 mmol). After the solution was purged with
nitrogen for 10 min, BF3·OEt2 (0.075 mL) was added via a
syringe. The mixture was stirred at room temperature under
nitrogen atmosphere and monitored by TLC. After 1 h,
DDQ (1.13 g, 5 mmol) dissolved in benzene (50 mL) was
added and the solution was further stirred at room
temperature for 1.5 h. Elimination of the insoluble solid
by filtration, the filtrate was concentrated and loaded on
Al2O3 (100 g) column, the crude products were eluted by
CHCl3. The bisporphyrin was further purified on silica gel
column (chloroform–hexane), then concentrated and dried.
Yield, 0.18 g, 23%. [Found: C, 75.62; H, 6.23; N, 6.87.
C100H102N8Si6 requires C, 75.81; H, 6.44; N, 7.08%]; nmax
(KBr) 3450–3410, 3180, 2953, 1637, 1597, 1559, 1400,
Acknowledgements
We are grateful to the Japan Society for the Promotion of
Science (JSPS) and the Ministry of Education of China for a
grant for Returned Scientists from Abroad (B. H. Y.) for
financial support. This work was also supported by the
Grants-in-Aid for COE Research (#08CE2005) and for
Science Research on Priority Areas (#09235225 and
11228207) from MEXT and for Scientific Research (A)
(#14204073) from JSPS.
1249, 1108, 981, 966, 839, 798, 755, 731, 696, 624 cm21
;
dH (400 MHz, CDCl3) 9.16 (4H, d, J¼4.9 Hz), 8.84–8.82
(2H, m), 8.37–8.35 (12H, m), 8.27–8.24 (2H, m), 7.99 (2H,
d, J¼6.8 Hz), 7.77–7.69 (16H, m), 7.56–7.51 (4H, m), 7.43
(2H, d, J¼6.3 Hz), 0.496 (36H, s), 0.363 (18H, s), 23.87
(4H, br). ESI-MS: found 1584 (100%). C100H103N8Si6
[MþH]þ requires 1584. UV–vis: lmax/nm (CH2Cl2): 408,
524, 554, 599, 655.
References
1. Hambright, P. The Porphyrin Handbook: Chemistry of Water

B.-H. Ye, Y. Naruta / Tetrahedron 59 (2003) 3593–3601
3601
Soluble Porphyrins; Kadish, K. M., Smith, K. M., Guilard, R.,
Eds.; Academic: New York, 2000; Vol. 3, pp 130–210.
2. Song, R.; Witvrouw, M.; Robert, A.; Balzarini, J.; Clereq,
E. De.; Bernadou, J.; Meunier, B. Antivir. Chem. Chemoth.
1997, 8, 85–97.
22. Gonsalves, A. M. d’A. R.; Johnstone, R. W. A.; Pereira, M. M.;
de SantAna, A. M. P.; Serra, A. C.; Sorbal, A. J. F. N.; Stocks,
P. A. Heterocycles 1996, 43, 829–838.
23. Felix, G.; Dunogues, J.; Calas, R. Angew. Chem. Int. Ed. Engl.
1979, 18, 402–404.
3. Fiel, R. J.; Mark, E. H.; Button, T. M.; Gilani, S.; Musser, D. A.
Cancer Lett. 1988, 40, 23–32.
24. Stephens, E. B.; Kinsey, K. E.; Davis, J. F.; Tour, J. M.
Macromolecules 1993, 26, 3519–3532.
4. Maderna, A.; Huertas, R.; Hawthorne, M. F.; Luguya, R.;
Vicente, M. G. H. Chem. Commun. 2002, 1784–1785.
5. Fiel, R. J.; Musser, D.; Mark, E.; Mazurchuk, R.; Alleto, J. J.
Magn. Reson. Imaging 1990, 8, 255–259.
25. Lindsey, J. S.; Schreiman, I. C.; Hsu, H. C.; Kearney, P. C.;
Marguerttaz, A. M. J. Org. Chem. 1987, 52, 827–836.
26. Lindsey, J. S.; Wagner, R. W. J. Org. Chem. 1989, 54,
828–836.
6. Labat, G.; Meunier, B. J. Org. Chem. 1989, 54, 5008–5011.
7. Labat, G.; Meunier, B. Chem. Commun. 1990, 1414–1416.
8. Labat, G.; Seris, J. L.; Meunier, B. Angew. Chem. Int. Ed.
Engl. 1990, 29, 1488–1490.
27. Reetz, M. T.; Gosberg, A. Tetrahedron: Asymmetry 1999, 10,
2129–2137.
28. Kruper, W. J.; Chamberlin, T. A.; Kochanny, J. J. Org. Chem.
1989, 54, 2753–2756.
9. Holman, K. T.; Pivovar, A. M.; Ward, M. D. Science 2001,
294, 1907–1911.
29. Harriman, A.; Porter, G. J. Chem. Soc., Faraday Trans. 1979,
2, 1532–1542.
10. Mizutani, T.; Wada, K.; Kitagawa, S. J. Am. Chem. Soc. 1999,
121, 11425–11431.
30. Jimenez, H. R.; Julve, M.; Moratal, J. M.; Faus, J. Chem.
Commun. 1987, 910–911.
11. Fermin, D. J.; Duong, H. D.; Ding, Z. F.; Brevet, P. F.; Girault,
H. H. J. Am. Chem. Soc. 1999, 121, 10203–10210.
12. Vinogradov, S. A.; Wilson, D. F. J. Chem. Soc., Perkin Trans.
2 1995, 103–111.
31. Srivastava, T. S.; Tsutsui, M. J. Org. Chem. 1973, 38,
2103–2103.
32. Busby, C. A.; Dinello, R. K.; Dolphin, D. Can. J. Chem. 1975,
53, 1554–1555.
13. Tabata, M.; Nishimoto, J.; Kusano, T. Talanta 1998, 46,
703–709.
33. Shimazaki, Y.; Takesue, H.; Chishiro, T.; Tani, F.; Naruta, Y.
Chem. Lett. 2001, 538–539.
14. Sun, H. P.; Tabata, M. Talanta 1999, 49, 603–610.
15. Fleisher, E. B.; Palmer, J. M.; Srivastava, S. T.; Chatterjee, A.
J. Am. Chem. Soc. 1971, 93, 3162–3167.
34. Fletcher, J. T.; Therien, M. J. Inorg. Chem. 2002, 41,
331–341.
35. Fletcher, J. T.; Therien, M. J. J. Am. Chem. Soc. 2000, 122,
12393–12394.
16. Hoffman, P.; Labat, G.; Robert, A.; Meunier, B. Tetrahedron
Lett. 1990, 31, 1991–1994.
36. Osuka, A.; Nakajima, S.; Nagata, T.; Maruyama, K.; Toriumi,
K. Angew. Chem. Int. Ed. Engl. 1991, 30, 582–584.
37. Meier, H.; Kobuke, Y.; Kugimiya, S. Chem. Commun. 1989,
923–924.
17. Panicuccu, R.; Bruice, T. C. J. Am. Soc. Chem. 1990, 112,
6063–6071.
18. Turk, H.; Ford, W. T. J. Org. Chem. 1991, 56, 1254–1260.
19. Sutter, T. P. G.; Rahimi, R.; Hambright, P.; Bommer, J.;
Kumar, M.; Neta, P. J. Chem. Soc., Faraday Trans. 1993,
495–502.
38. Attenburrow, J.; Cameron, A. F. B.; Chapman, J. H.; Evans,
K. M.; Hems, B. A.; Jansen, A. B. A.; Walker, T. J. Chem. Soc.
1952, 1094–1111.
20. Meng, G. G.; James, B. R.; Skov, K. A.; Korbeilik, M. Can.
J. Chem. 1994, 72, 2447–2457.
39. Osuka, A.; Nakajima, S.; Maruyama, K. J. Org. Chem. 1992,
57, 7355–7359.
21. Meng, G. G.; James, B. R.; Skov, K. A. Can. J. Chem. 1994,
72, 1894–1909.