Synthesis of 2,3-dihydrobenzo[1,4]dithiin-fused porphyrins

Article abstract of DOI:10.1080/10426501003773449

This article describes the preparation of (ethylenedithio)bicyclo[2.2.2] octadiene-fused porphyrins 13 and 14a,b as soluble precursors of 2,3-dihydrobenzo[1,4]dithiin-fused porphyrins and the retro Diels-Alder conversion of the precursors 13 and 14a,b. Co

Full text of DOI:10.1080/10426501003773449

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Phosphorus, Sulfur, and Silicon and the
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Synthesis of 2,3-
Dihydrobenzo[1,4]dithiin-Fused
Porphyrins
Guangnan Jin a , Tetsuo Okujima a , Yusuke Hashimoto a , Hiroko
Yamada a b , Hidemitsu Uno c & Noboru Ono a
a Department of Chemistry and Biology, Graduate School of Science
and Engineering , Ehime University , Matsuyama, Japan
b PRESTO , Japan Science and Technology Agency , Kawaguchi,
Japan
c Department of Molecular Science, Integrated Center for Science ,
Ehime University , Matsuyama, Japan
Published online: 27 May 2010.
To cite this article: Guangnan Jin , Tetsuo Okujima , Yusuke Hashimoto , Hiroko Yamada , Hidemitsu
Uno & Noboru Ono (2010) Synthesis of 2,3-Dihydrobenzo[1,4]dithiin-Fused Porphyrins, Phosphorus,
Sulfur, and Silicon and the Related Elements, 185:5-6, 1108-1116, DOI: 10.1080/10426501003773449
To link to this article: http://dx.doi.org/10.1080/10426501003773449
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Phosphorus, Sulfur, and Silicon, 185:1108–1116, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003773449
SYNTHESIS OF 2,3-DIHYDROBENZO[1,4]DITHIIN-FUSED
PORPHYRINS
Guangnan Jin,1 Tetsuo Okujima,1 Yusuke Hashimoto,1
Hiroko Yamada,1,2 Hidemitsu Uno,3 and Noboru Ono1
1Department of Chemistry and Biology, Graduate School of Science and
Engineering, Ehime University, Matsuyama, Japan
2PRESTO, Japan Science and Technology Agency, Kawaguchi, Japan
3Department of Molecular Science, Integrated Center for Science, Ehime
University, Matsuyama, Japan
This article describes the preparation of (ethylenedithio)bicyclo[2.2.2]octadiene-fused por-
phyrins 13 and 14a,b as soluble precursors of 2,3-dihydrobenzo[1,4]dithiin-fused porphyrins
and the retro Diels–Alder conversion of the precursors 13 and 14a,b.
Keywords Benzo[1,4]dithiin; benzoporphyrin; retro Diels–Alder reaction; ring expansion
reaction of 1,3-dithiolane
INTRODUCTION
The π-conjugated porphyrins with exocyclic rings have been extensively studied
because of their special optical and electrical properties.1 Their chemistry has been inves-
tigated for the applications to photoelectronic materials and molecular devices.2 Alterna-
tively, numerous molecules with the ethylenedithio group have also attracted the interest
of the many research groups for the preparation of the organic ferromagnets. For example,
benzo[1,4]dithiin system or bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) is a well
known compound that gives the conducting radical ion salts.3–7 These dihydro-1,4-dithiin
rings are prepared by ring expansion reaction of 1,3-dithiolanes upon treatment with var-
ious reagents such as Br2,4,8 NBS,9 NCS,10 PhSeCl,11,12 or TeCl4.13,14 The 1,3-dithiolanes
can be obtained by the dithioacetalization of the corresponding carbonyl compounds with
1,2-ethanedithiol. Recently, we have reported the synthesis of 4,7-dihydro-2H-isoindoles
via Diels–Alder reaction of ethynyl p-tolyl sulfine with several 1,3-cyclohexadienes.15 The
Diels–Alder adduct with a trimethylsilyloxy group was converted into pyrrole with fused
Received 10 December 2008; accepted 26 December 2008.
Dedicated to Professor Naomichi Furukawa on the occasion of his 70th birthday.
This work was partially supported by the Sasagawa Scientific Research Grant from The Japan Science
Society (G.J.). We used ethyl isocyanoacetate from the Nippon Synthetic Chem. Ind. (Osaka Japan).
Address correspondence to Tetsuo Okujima, Department of Chemistry and Biology, Graduate School of
Science and Engineering, Ehime University, Matsuyama 790-8577, Japan. E-mail: tetsuo@chem.sci.ehime-u.ac.jp
1108

2,3-DIHYDROBENZO[1,4]DITHIIN-FUSED PORPHYRINS
1109
bicyclo[2.2.2]octenone by hydrolytic removal of the silyl group, acetalization, and the mod-
ified Barton–Zard reaction. Therefore, this pyrrole could be the key compound in the syn-
thesis of peripheral functionalized benzoporphyrins (BPs) by the substitution reaction of the
carbonyl moiety and the retro Diels–Alder reaction of the bicyclo[2.2.2]octadiene (BCOD)
moiety. We report in this article the synthesis of 4,7-ethano-5,6-ethylenedithio-4,7-dihydro-
2H-isoindoles 1a–c; the condensation of diformyltripyrrane 12 with 1a and the tetramer-
ization of 1c followed by the oxidation to give the corresponding porphyrins 13 and 14a,b;
and the retro Diels–Alder conversion of them into mono(4,5-ethylenedithio)benzoporphyrin
(MEDT-BP 2) and tetrakis(4,5-ethylenedithio)tetrabenzoporphyrins (TEDT-TBPs 3a,b) in
Chart 1.
Chart 1
RESULTS AND DISCUSSION
Synthesis of 5,6-ethylenedithioisoindole derivatives 1 is summarized in Scheme 1.
Bicyclo[2.2.2]octanone 6 was prepared by the Diels–Alder reaction of 2-trimethylsilyloxy-
1,3-cyclohexadiene (4) with trans-1,2-bis(phenylsulfonyl)ethylene (5) and the subsequent
desilylation in 76% yield.16 The thioacetalization of 6, followed by the ring expansion
reaction with TeCl4 as a Lewis acid oxidant gave 2,3-ethylenedithiobicyclo[2.2.2]oct-2-
ene 8, which was converted into the corresponding pyrrole 1b by the modified Barton–Zard
reaction.17,18 Removal of the ethoxycarbonyl group by heating 1b with NaOH in ethylene
glycol at 170◦C gave α-free pyrrole 1a in 49%. Pyrrole 1b was also prepared starting from
9 15 by the similar procedure as shown in Scheme 2.
Scheme 1

1110
G. JIN ET AL.
Scheme 2
19
The condensation of tripyrrane 12
with 1a in CHCl3 in the presence of TFA
followed by oxidation with p-chloranil gave 13 in 22% yield as shown in Scheme 3.
Tetrakis(ethylenedithioBCOD)porphyrin 14a was synthesized by reduction of 1b with
LiAlH4 followed by tetramerization and oxidation with p-chloranil (Scheme 4).20 Zinc
complex 14b was prepared on the treatment of 14a with zinc acetate.
Scheme 3
Scheme 4
The retro Diels–Alder reaction of 13 was carried out at 240◦C in vacuo in a glass tube
oven. MEDT-BP 2 was quantitatively obtained. Thermogravimetric analysis (TGA) curves
of 13 and 14a,b are shown in Figure 1. The weight loss of 13 started at around 200◦C and
ceased after 230◦C. The loss of weight was ca. 5%, consistent with the calculated value

2,3-DIHYDROBENZO[1,4]DITHIIN-FUSED PORPHYRINS
1111
Figure 1 TGA of 13 (bold line), 14a (solid line), and 14b (broken line).
of 4.2%. Tetrakis(ethylenedithioBCOD)porphyrins 14a and 14b were also converted into
TEDT-TBPs 3 by heating at 240◦C under same conditions in nearly quantitative yields.
The absorption and fluorescence spectra of 3a,b and 14a,b are shown in Figure 2. The
Soret band of 14b appeared at 404 nm, while that of 3b appeared at 442 nm. The absorption
maxima of 14a,b showed a bathochromic shift as they were converted into TEDT-TBPs
3a,b. The emission spectra of zinc complexes 3b and 14b with excitation at their Soret
bands showed a single band at 657 nm. The values of their absolute quantum yields (ꢀ) in
CHCl3 solution were in the range of 0.10–0.11. On the other hand, the emissions of free
base porphyrins 3a and 14a were observed at around 670 nm and 688 nm with ꢀ values of
0.24 and 0.16, respectively.
In summary, 2,3-dihydro-1,4-dithiin-fused BPs, MEDT-BP 2, and TEDT-TBPs
3a,b were synthesized from (ethylenedithioBCOD)porphyrins 13 and 14a,b by the retro
Diels–Alder reaction in nearly quantitative yield. Both the Soret and Q bands of 2 and
3a,b exhibited a bathochromic shift compared to their precursors 13 and 14a,b. Free base
Figure 2 Absorption and fluorescence emission (inset) spectra of 3a (dotted line), 3b (broken line), 14a (bold
line), and 14b (solid line) in CHCl3.

1112
G. JIN ET AL.
porphyrin 3a fluoresces with ꢀ values of up to 0.25. Further works on application of these
porphyrins such as solution-processed fabrication for organic field-effect transistors are
underway.
EXPERIMENTAL
Melting points were determined on a Yanaco micro melting point apparatus MP500D
and are reported here uncorrected. DI-EI and FAB mass spectra were measured on a JEOL
JMS-700. TG analyses were performed on an SII Exstar 600 TG/DTA 6200. UV-vis spectra
were measured on a JASCO V-570 spectrophotometer. The fluorescence emission spectra
and the ꢀ values were measured on a Hamamatsu Photonics K.K. absolute PL quantum
yield measurement system C9920–03. 1H NMR spectra (13C NMR spectra) were recorded
on a JEOL AL-400 at 400 MHz (100 MHz). Elemental analyses were performed at the
Integrated Center for Sciences, Ehime University.
5,6-Bis(phenylsulfonyl)bicyclo[2.2.2]octan-2-one (6)16
A solution of 4 (4.0 mL, 21 mmol) and 5 (3.05 g, 9.89 mmol) in toluene (80 mL)
was heated at 130◦C in an autoclave for 5 d. After addition of silica gel (ca. 20 g), the
resulting mixture was stirred at room temperature overnight. The reaction mixture was
filtered with Celite and concentrated under reduced pressure. The residue was purified
by column chromatography on silica gel with CHCl3 followed by recrystallization from
CHCl3/hexane to give 6 (3.05 g, 76%) as colorless crystals.
2,3-Ethylenedithio-5,6-bis(phenylsulfonyl)bicyclo[2.2.2]oct-2-ene (8)
To a solution of 6 (8.08 g, 20.0 mmol) in dry CH2Cl2 (40 mL), 1,2-ethanedithiol (4.0
ml, 48 mmol) and powdered AlCl3 (0.95 g, 7.1 mmol) were added. The resulting mixture
was stirred at room temperature for 2 h. The reaction was quenched with sat. aqueous
NaHCO3, and the insoluble material was removed by filtration with Celite. The filtrate was
extracted with CH2Cl2. The organic layer was washed with brine, dried over Na2SO4, and
concentrated under reduced pressure. After addition of ether, the mixture was cooled in
a refrigerator overnight. The precipitate was collected by filtration as crude thioacetal 7
(9.22 g).
To a solution of crude 7 (4.81 g) in dry CH2Cl2 (40 mL), powdered TeCl4 (1.92 g,
7.13 mmol) was added at 0◦C. After stirring at room temperature for 2 h, sat. aqueous
NaHCO3 was poured into the reaction mixture. The resulting black precipitate was removed
by filtration with Celite. The filtrate was washed with brine, dried over Na2SO4, and
concentrated under reduced pressure. The residue was purified by column chromatography
on silica gel with CHCl3 followed by recrystallization from CH2Cl2/hexane to give 8
(3.69 g, 74%).
Colorless crystals; mp 198.2–200.1◦C; MS (FAB) m/z 478 (M++H); 1H NMR (400
MHz, CDCl3) δ 7.93 (m, 2H), 7.84 (m, 2H), 7.68 (m, 1H), 7.65 (m, 1H), 7.59 (m, 2H), 7.54
(m, 2H), 3.90 (dd, 1H, J = 2.2, 5.6 Hz), 3.83 (m, 1H), 3.14–3.26 (m, 4H), 3.04 (dd, 1H,
J = 2.7, 5.6 Hz), 2.69 (m, 1H), 2.35 (m, 1H), 1.70 (m, 1H), 1.62 (m, 1H), and 1.41 (m, 1H);
13C NMR (100 MHz, CDCl3) δ 139.04, 137.64, 133.98, 133.90, 129.10, 129.07, 128.99,
128.66, 123.89, 123.21, 65.74, 62.70, 39.03, 38.87, 28.27, 28.14, 24.96, and 21.67. Anal.
Calcd for C22H22O4S4: C, 55.20; H, 4.63. Found: C, 54.92; H, 4.62.

2,3-DIHYDROBENZO[1,4]DITHIIN-FUSED PORPHYRINS
1113
2,3-Ethylenedithio-5-tosylbicyclo[2.2.2]octa-2,5-diene (11)
To a solution of 9 (0.91 g, 3.3 mmol) in dry CH2Cl2 (10 mL), 1,2-ethanedithiol
(0.35 ml, 4.2 mmol) and powdered AlCl3 (165 mg, 1.24 mmol) were added. The resulting
mixture was stirred at room temperature overnight. The reaction was quenched with sat.
aqueous NaHCO3, and the insoluble material was removed by filtration with Celite. The
filtrate was extracted with CH2Cl2. The organic layer was washed with brine, dried over
Na2SO4, and concentrated under reduced pressure. After addition of ether, the mixture
was cooled in a refrigerator overnight. The precipitate was collected by filtration as crude
thioacetal 10 (0.84 g).
To a solution of crude 10 (0.36 g) in dry CH2Cl2 (10 mL), powdered TeCl4 (259 mg,
0.961 mmol) was added at 0◦C. After stirring at room temperature for 0.5 h, sat. aqueous
NaHCO3 was poured into the reaction mixture. The resulting black precipitate was removed
by filtration with Celite. The filtrate was washed with brine, dried over Na2SO4, and
concentrated under reduced pressure. The residue was purified by column chromatography
on silica gel with CHCl3 followed by recrystallization from CH2Cl2/hexane to give 11
(0.22 g, 44%).
Colorless crystals; mp 117.2–118.6◦C; MS (FAꢁB) m/z 350 (M++H); 1H NMR (400
ꢁ
ꢁ
ꢁ
MHz, CDCl3) δ 7.72 (m, 2H, H2 ,6 ), 7.31 (m, 2H, H3 ,5 ), 7.23 (dd, 1H, J = 2.1, 6.3 Hz, H6),
3.60 (dd, 1H, J = 2.6, 4.8 Hz, H4), 3.52 (ddd, 1H, J = 2.6, 2.6, 6.3 Hz, H1), 2.98–3.06 (m,
4H, -SCH2CH2S-), 2.42 (s, 3H, CH3), 1.64 (m, 1H, H7 or H8), 1.54 (m, 1H, H8 or H7), 1.41
(m, 1H, H7 or H8), and 1.27 (m, 1H, H8 or H7); 13C NMR (100 MHz, CDCl3) δ 146.23,
144.04, 142.57, 136.55, 129.67, 127.64, 123.92, 123.55, 44.67, 43.72, 27.79, 27.69, 26.73,
25.94, and 21.63. Anal. Calcd for C17H18O2S3: C, 58.25; H, 5.18. Found: C, 57.95; H, 5.06.
Ethyl 4,7-Ethano-5,6-ethylenedithio-4,7-dihydro-2H-isoindole-
1-carboxylate (1b)
From 8. A solution of potassium t-butoxide (1.34 g) in dry THF (15 mL) was added
to a stirred solution of 8 (2.44 g, 5.10 mmol) and ethyl isocyanoacetate (1.3 mL) in dry
THF (30 ml) at 0◦C under an Ar atmosphere. The resulting mixture was stirred at room
temperature for 21 h. The reaction mixture was poured into 1 M HCl (10 mL), evaporated
and extracted with CHCl3. The organic layer was washed successively with sat. aqueous
NaHCO3, water, and brine; dried over Na2SO4; and concentrated under reduced pressure.
The residue was purified by column chromatography on silica gel with CHCl3 followed by
recrystallization from CHCl3/methanol to give 1b (1.43 g, 91%).
From 11. The above procedure was followed by using 11 (83 mg, 0.24 mmol), ethyl
isocyanoacetate (0.1 ml) in dry THF (7 mL), and 1 M potassium t-butoxide solution in dry
THF (2 mL). Chromatographic purification on silica gel with CHCl3 and recrystallization
from CHCl3/hexane gave 1b (56 mg, 77%)
Colorless crystals; mp 189.5–191.4◦C; MS (70 eV) m/z (relative intensity) 307 (M+,
1
44%), 279 (M+–C2H4, 85), and 233 (100); H NMR (400 MHz, CDCl3) δ 8.50 (br, 1H,
NH), 6.58 (d, 1H, J = 2.7 Hz, H3), 4.31 (q, 2H, J = 7.1 Hz, 1-CO2Et), 4.10 (m, 1H, H4),
3.60 (m, 1H, H7), 3.12 (s, 4H, -SCH2CH2S-), 1.82 (m, 2H, H8 and H9), 1.52 (m, 2H, H8
and H9), and 1.36 (t, 3H, J = 7.1 Hz, 1-CO2Et); 13C NMR (100 MHz, CDCl3) δ 161.40,
134.58, 129.87, 126.16, 125.32, 114.11, 112.73, 60.00, 40.95, 40.66, 28.49, 28.00, 27.97,
27.87, and 14.59. Anal. Calcd for C15H17NO2S2: C, 58.60; H, 5.57; N, 4.56. Found: C,
58.34; H, 5.60; N, 4.59.

1114
G. JIN ET AL.
4,7-Ethano-5,6-ethylenedithio-4,7-dihydro-2H-isoindole (1a)
A solution of 1b (464 mg, 1.51 mmol) and NaOH (375 mg) in ethylene glycol (10 mL)
was heated at 170◦C for 1.5 h under an Ar atmosphere in a shaded vessel. The reaction
mixture was poured into water and extracted with CHCl3. The organic layer was washed
successively with water and brine, dried over Na2SO4, and concentrated under reduced
pressure. The residue was purified by column chromatography on silica gel with CHCl3
and washed with CHCl3/hexane to give 1a (173 mg, 49%).
Colorless crystals; mp 180.0–182.0◦C; MS (FAB) m/z 235 (M+) and 207 (M+–C2H4);
1H NMR (400 MHz, CDCl3) δ 7.57 (br, 1H, NH), 6.46 (d, 2H, J = 2.4 Hz, H1,3), 3.59 (m,
2H, H4,7), 3.11 (s, 4H, -SCH2CH2S-), 1.82 (m, 2H, H8 and H9), and 1.55 (m, 2H, H8 and
H9); 13C NMR (100 MHz, CDCl3) δ 127.88, 126.03, 108.05, 40.73, 29.00, and 27.97. Anal.
Calcd for C12H13NS2: C, 61.24; H, 5.57; N, 5.95. Found: C, 61.03; H, 5.44; N, 5.86.
Mono(ethylenedithioBCOD)porphyrin 13
To a solution of 12 (233 mg, 0.488 mmol) and 1a (118 mg, 0.503 mmol) in dry CH2Cl2
(30 mL), TFA (1 mL) was added at room temperature under an Ar atmosphere in a shaded
vessel. After stirring overnight, the reaction mixture was neutralized with triethylamine,
treated with p-chloranil (0.12 g, 0.49 mmol) for 4 h with stirring at room temperature,
and evaporated. After dilution with CHCl3, the mixture was washed successively with sat.
aqueous NaHCO3, water, and brine; dried over Na2SO4; and concentrated under reduced
pressure. The residue was purified by column chromatography on silica gel with CHCl3
followed by recrystallization from hexane to give 13 (72 mg, 22%).
Purple crystals; mp > 200◦C (decomp); MS (FAB) m/z 675 (M++H); UV-vis (CHCl3)
λmax (nm) 398, 498, 535, 567, and 621; 1H NMR (400 MHz, CDCl3) δ 10.15 (s, 2H), 10.10
(s, 2H), 5.41 (s, 2H), 4.04–4.14 (m,8H), 3.64 (s, 6H), 3.19–3.35 (m, 4H), 2.45 (m, 2H),
2.27 (tt, 4H, J = 7.3, 7.6 Hz), 1.97 (m, 2H), 1.93 (t, 6H, J = 7.6 Hz), 1.74 (tq, 4H, J =
7.3, 7.3 Hz), 1.11 (t, 6H, J = 7.3 Hz), and -3.95 (br, 2H). HRMS calcd for C42H51N4S2
675.3555, found 675.3558.
Tetrakis(ethylenedithioBCOD)porphyrin 14a
LiAlH4 (78 mg, 2.1mmol) was added slowly to a solution of 1b (0.16 g, 0.52 mmol) in
dry THF (15 ml) at 0◦C under an Ar atmosphere in a shaded vessel, and the resulting mixture
was stirred for 2 h. After slow addition of water, the precipitate was removed by filtration
with Celite. The filtrate was extracted with ethyl acetate. The organic layer was washed
successively with water and brine, dried over Na2SO4, and concentrated under reduced
pressure. The residue was diluted with CHCl3 (150 mL). After addition of p-TsOH·H2O
(10 mg), the mixture was stirred at room temperature for 12 h, after which p-chloranil
(0.16 g, 0.65 mmol) was added. After stirring for 1 day, the reaction mixture was washed
successively with aqueous NaHCO3 and brine, dried over Na2SO4, and concentrated under
reduced pressure. The residue was purified by column chromatography on silica gel with
CHCl3 followed by recrystallization from CHCl3/methanol to give 14a (65 mg, 51%).
Purple crystals; mp > 200◦C (decomp); MS (FAB) m/z 984 (M++H); UV-vis (CHCl3)
λmax (nm) (log ε) 398 (5.28), 498 (4.28), 530 (3.89), 566 (3.86), and 618 (3.11); 1H NMR
(400 MHz, CDCl3) δ 10.32 (s, 4H), 5.47 (br, 8H), 3.27–3.34 (m, 8H), 3.15–3.26 (m, 8H),
2.45–2.51 (m, 8H), 1.93–2.09 (m, 8H), and −4.61 (br, 2H). HRMS calcd for C52H47N4S8

2,3-DIHYDROBENZO[1,4]DITHIIN-FUSED PORPHYRINS
1115
983.1566, found 983.1568. Anal. Calcd for C52H46N4S8: C, 63.51; H, 4.71; N, 5.70. Found:
C, 63.65; H, 4.74; N, 5.41.
[Tetrakis(ethylenedithioBCOD)porphyrinato]zinc 14b
A saturated solution of Zn(OAc)2·2H2O in methanol (20 mL) was added to a solution
of 14a (64 mg, 0.065 mmol) in CHCl3 (20 mL) at room temperature under an Ar atmo-
sphere in a shaded vessel. The resulting mixture was stirred at same temperature for 16 h.
The reaction mixture was poured into water. The organic layer was washed successively
with water and brine, dried over Na2SO4, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel with CHCl3 followed by
recrystallization from CHCl3/methanol to give 14b (26 mg, 39%).
Purple crystals; mp > 200◦C (decomp); MS (FAB) m/z 1046 (M+); UV-vis (CHCl3)
λmax (nm) 404, 530, and 563;1H NMR (400 MHz, CDCl3) δ 10.40 (s, 4H), 5.51 (br, 8H),
3.29–3.36 (m, 8H), 3.16–3.23 (m, 8H), 2.50–2.54 (m, 8H), and 2.02–2.12 (m, 8H). HRMS
calcd for C52H45N4S866Zn 1047.0670, found 1047.0668.
General Procedure for the Retro Diels–Alder Reaction
(EthylenedithioBCOD)porphyrins 13 and 14a,b (ca. 10 mg) were heated at 240◦C
under reduced pressure in a glass tube to give MEDT-BP 2 and TEDT-TBPs 3a,b, respec-
tively.
2: Purple crystals; mp > 250◦C; MS (FAB) m/z 647 (M++H); UV-vis (CHCl3) λmax
(nm) 413, 509, 548, 577, and 632; 1H NMR (400 MHz, CDCl3) δ 10.20 (s, 2H), 10.06 (s,
2H), 9.16 (s, 2H), 4.13 (t, 4H, J = 7.6 Hz), 4.01 (q, 4H, J = 7.6 Hz), 3.68 (s, 6H), 3.58
(s, 4H), 2.28 (tt, 4H, J = 7.3, 7.6 Hz), 1.89 (t, 6H, J = 7.6 Hz), 1.74 (tq, 4H, J = 7.3, 7.3
Hz), 1.12 (t, 6H, J = 7.3 Hz), and -3.67 (br, 2H). HRMS calcd for C40H47N4S2 647.3242,
found 647.3245.
3a: Purple crystals; mp > 250◦C; MS (FAB) m/z 871 (M++H); UV-vis (CHCl3) λmax
(nm) 431, 451, 585, 642, and 684. HRMS calcd for C44H31N4S8 871.0314, found 871.0310.
Anal. Calcd for C44H30N4S8: C, 60.66; H, 3.47; N, 6.43. Found: C, 60.52; H, 3.58; N, 6.43.
3b: Purple crystals; mp > 250◦C; MS (FAB) m/z 934 (M+); UV-vis (CHCl3) λmax
(nm) 415, 442, and 651. HRMS calcd for C44H29N4S866Zn 934.9418, found 934.9422.
Anal. Calcd for C44H28N4S8Zn: C, 56.54; H, 3.02; N, 5.99. Found: C, 56.25; H, 3.22; N,
5.97.
REFERENCES
1. T. D. Lash, In The Porphyrin Handbook, K. M. Kadish, K. M. Smith, and R. Guilard, Eds.
(Academic Press, San Diego, 2000), vol. 2, Chap. 10, pp. 125–199.
2. J.-H. Chou, M. E. Kosal, H. S. Nalwa, N. A. Rakow, and K. S. Suslick, In The Porphyrin
Handbook, K. M. Kadish, K. M. Smith, and R. Guilard, Eds. (Academic Press, San Diego,
2000), vol. 6, Chap. 41, pp. 43–131.
3. S. Murru, V. Kavala, C. B. Singh, and B. K. Patel, Tetrahedron Lett., 48, 1007 (2007).
4. R. Caputo, C. Ferreri, G. Palumbo, and F. Russo, Tetrahedron, 47, 4187 (1991).
5. R. Lapouyade and J.-P. Morand, J. Chem. Soc., Chem. Commun., 223 (1987).
6. P. Day, C. R. Chimie, 6, 301 (2003).
7. H. Kobayashi, Curr. Opin. Solid State Mater. Sci., 2, 440 (1997).

1116
G. JIN ET AL.
8. R. Capuro, C. Ferreri, and G. Palumbo, Synthesis, 223 (1991).
9. R. Capuro, G. Palumbo, and S. Pedatella, Tetrahedron, 50, 7265 (1994).
10. K. Nakasuji, M. Sasaki, T. Kotani, I. Murata, T. Enoki, K. Imaeda, H. Inokuchi, A. Kawamoto,
and J. Tanaka, J. Am. Chem. Soc., 109, 6970 (1987).
11. C. G. Francisco, R. Freire, R. Herna´ndez, J. A. Salazar, and E. Sua´rez, Tetrahedron Lett., 25,
1621 (1984).
12. J. R. Williams and P. B. Tran, Synthesis, 705 (1988).
13. H. Tani, T. Inamasu, R. Tamura, and H. Suzuki, Chem. Lett., 19, 1323 (1990).
14. H. Tani, Bull. Chem. Soc. Jpn., 68, 661 (1995).
15. T. Okujima, G. Jin, Y. Hashimoto, H. Yamada, H. Uno, and N. Ono, Heterocycles, 70, 619 (2006).
16. O. De Lucchi, V. Lucchini, M. Zamai, G. Modena, and G. Valle, Can. J. Chem., 62, 2487 (1984).
17. D. H. R. Barton, J. Kevagoret, and S. Z. Zard, Tetrahedron, 46, 7587 (1990).
18. Review: N. Ono, Heterocycles, 75, 243 (2008).
19. S. Ito, K.-i. Nakamoto, H. Uno, T. Murashima, and N. Ono, Chem. Commun., 2696 (2001).
20. N. Ono and K. Maruyama, Chem. Lett., 17, 1511 (1988).