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DOI: 10.1055/s-0029-1218564
Borylated Thiaporphyrin Building Blocks for the Synthesis of Unsymmetrical Phenyl-Bridged Porphyrin Dyads
Publication History
Publication Date:
10 December 2009 (online)
Abstract
meso-(4-Borylphenyl)thiaporphyrin building blocks with N3S and N2S2 porphyrin cores have been synthesized using two different approaches and used for the synthesis of meso-meso- and β-meso-1,4-phenylene-bridged unsymmetrical porphyrin dyads containing two different porphyrin subunits.
Key words
thiaporphyrins - borylation - building blocks - porphyrin dyads - energy transfer
- Supporting Information for this article is available online:
- Supporting Information
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References and Notes
Experimental Procedure
and Spectroscopic Data for Selected Compounds. Diol 3: Thiophene mono-alcohol 4 (0.96
g, 4.7 mmol), TMEDA (1.76 mL, 11.7 mmol) and n-BuLi
(7.34 mL, ˜15% in hexane) were added successively
to freshly distilled anhydrous Et2O (30 mL) in a 250-mL
three-necked, round-bottomed flask and stirred for 45 min under nitrogen
atmosphere at 0 ˚C. An ice-cold solution of 4-formylboronic
ester (1.25 g, 5.7 mmol) in THF (30 mL) was added and the mixture
was stirred for an additional 45 min. The reaction was quenched
with ice-cold NH4Cl (50 mL, ˜1 M) and the organic
layer was separated from the aqueous layer. The aqueous layer was
extracted several times with Et2O and the combined organic
layers were washed thoroughly with water and brine and dried with
anhydrous Na2SO4. The solvent was removed
on a rotary evaporator under reduced pressure to afford the crude
compound. TLC analysis showed three minor and one major spot corresponding
to the unreacted 4-formylphenylboronic ester, unreacted mono-alcohol 4, unidentified compound and the desired
diol 3. The crude compound was subjected
to silica gel column chromatography (petroleum ether-EtOAc, 80:20).
The aldehyde, the mono-alcohol 4 and the
minor unidentified compound were removed and the desired diol 3 was collected (petroleum ether-EtOAc,
70:30) as yellow oily liquid (0.60 g, 30%). ¹H
NMR (400 MHz, CDCl3): δ = 1.03 (s,
6 H, CH3), 2.34 (s, 3 H, CH3), 3.50 (br s,
2 H, OH), 3.76 (s, 4 H, CH2), 5.92-5.96 (m,
2 H, CHOH), 6.67-6.69 (m, 2 H, thiophene), 7.28-7.30
(m, 2 H, ArH), 7.40 (d, J = 7.0
Hz, 2 H, ArH), 7.77-7.79 (m, 4 H, ArH). ¹³C
NMR (100 MHz, CDCl3): δ = 22.5, 65.8,
71.5, 120.1, 124.3, 124.5, 125.5, 128.1, 129.3, 134.6, 136.1, 139.5,
140.2, 143.7, 145.6, 146.0, 149.7, 152.8, 155.6 ppm. ES-MS: m/z calcd
for C24H27BO4S: 422.1; found: 351.1
(100) [M - C5H11]+.
Anal. Calcd for C24H27BO4S: C,
68.25; H, 6.44. Found: C, 68.30; H, 6.37.
Porphyrin 6: A solution of diol 3 (0.5
g, 1.2 mmol), p-tolualdehyde (0.3 mL,
2.4 mmol) and pyrrole (0.25 mL, 3.6 mmol) in CH2Cl2 (300
mL) were condensed in the presence of BF3˙OEt2 (396
mL, 2.5 M) under an inert atmosphere. After 1 h, DDQ (0.272 g, 1.2
mmol) was added and the reaction was stirred in open air for an
additional 1 h. TLC analysis indicated the formation of a mixture
of four porphyrins: tetra(p-tolyl)porphyrin
(H2TTP), the desired mono-functionalized 21-thiaporphyrin
boronic acid 6 and a cis and trans mixture of 21,23-dithiaporphyrin
boronic acid. The crude mixture of porphyrins was subjected to silica
gel column chromatography and the fast moving H2TTP was removed
with petroleum ether-CH2Cl2 (80:20).
The desired 6 was collected as a second
band using petroleum ether-CH2Cl2 (40:60)
and the cis and trans mixture
of porphyrins was collected in CH2Cl2. The
solvent was removed on a rotary evaporator to afford H2TTP
(3%), the desired compound 6 (8%)
and the cis and trans mixture
(<1%). ¹H NMR (400 MHz, CDCl3): δ = -2.69 (s, 1 H, NH), 2.69 (s,
9 H, CH3), 7.23 (d, J = 8.2
Hz, 2 H, ArH), 7.54 (d, J = 7.6
Hz, 4 H, ArH), 7.61 (d, J = 7.6
Hz, 2 H, ArH), 8.06-8.14 (m, 8 H, ArH), 8.67 (d, J = 4.6 Hz,
2 H, β-pyrrole), 8.68 (d, J = 4.6 Hz,
2 H, β-pyrrole), 8.93 (s, 2 H, β-pyrrole),
9.75 (s, 2 H, β-thiophene). ¹³C
NMR (100 MHz, CDCl3): δ = 21.8, 31.2,
103.2, 120.9, 121.3, 123.6, 128.4, 128.5, 129.2, 130.4, 133.2, 134.3,
134.7, 135.2, 135.9, 136.9, 138.1, 138.4, 145.8, 148.3, 154.1, 156.8,
157.1, 157.6. ES-MS: m/z calcd for C47H36BN3O2S:
717.3; found: 718.3 (100%) [M + 1]+. UV/Vis
(CH2Cl2): λmax (log ε) = 431
(5.89), 515 (4.59), 551 (4.16), 619 (3.66), 680 nm (3.95).
Porphyrin 7: Samples of diol 3 (0.4
g, 0.95 mmol) and tripyrrane 5 (0.398 g,
0.95 mmol) in CH2Cl2 (250 mL) were condensed
in the presence of BF3˙OEt2 (200
mL, 2.5 M) under inert atmosphere for 1 h. DDQ (0.216 g, 0.95 mmol) was
added and stirring was continued for additional 1 h in open air.
TLC analysis showed the formation of the desired product 7 as the sole product. Chromatography on
silica (petroleum ether-CH2Cl2, 50:50)
gave porphyrin 7 as a purple solid (0.08
g, 11%). ¹H NMR (400 MHz, CDCl3): δ = 2.70
(s, 9 H, CH3), 7.21 (d, J = 7.6
Hz, 2 H, ArH), 7.61 (d, J = 7.6
Hz, 6 H, ArH), 8.08 (d, J = 7.6
Hz, 6 H, ArH), 8.23 (s, 2 H, ArH), 8.67 (s, 4 H, β-pyrrole),
9.95 (s, 4 H, β-thiophene). ¹³C
NMR (100 MHz, CDCl3): δ = 22.6, 22.8, 31.1,
31.5, 128.0, 129.5, 133.6, 134.7, 134.9, 135.1, 135.7, 136.1, 138.0,
146.8, 147.6, 148.5, 148.7, 149.8, 150.9, 155.1, 157.1. ES-MS: m/z calcd
for C47H35BN2O2S2:
734.2; found: 735.6 (100%) [M + 1]+.
UV/Vis (CH2Cl2): λmax (log ε) = 437
(5.83), 515 (4.67), 550 (4.27), 634 (3.55), 698 nm (4.01).
Porphyrin 1: Method 1: Compound 6 (0.04
g, 0.055 mmol) was treated with 2,2-dimethylpropane-1,3-diol (0.009
g, 0.083 mmol) in THF (15 mL) at r.t. for 2 h. Flash column chromatography
(CH2Cl2) afforded porphyrin boronic ester 1 in 97% yield.
Borylated
thiaporphyrin building blocks for the synthesis of unsymmetrical
phenyl bridged porphyrin dyads: Method 2: The meso-brominated
thiaporphyrin 10 (0.03 g, 0.044 mmol) was
treated with phenyl diboronic ester 12 (0.04
g, 0.13 mmol) in toluene-triethylamine (5:1) in the presence
of catalytic amounts of Pd(PPh3)4 (0.005 g,
0.004 mmol) and Cs2CO3 (0.016 g, 0.066 mmol)
at 80 ˚C for 2 h. After standard work-up, the
crude compound was purified by silica gel column chromatography
(petroleum ether-CH2Cl2, 60:40) to
afford the porphyrin boronic ester 1 in
51% yield. ¹H NMR (400 MHz, CDCl3): δ = -2.69 (s, 1 H, NH), 1.16 (s, 6
H, CH3), 2.69 (s, 9 H, CH3), 3.93 (s, 4 H,
CH2), 7.23 (d, J = 8.2
Hz, 2 H, ArH), 7.54 (d, J = 7.6
Hz, 4 H, ArH), 7.61 (d, J = 7.6
Hz, 2 H, ArH), 8.06-8.14 (m, 8 H, ArH), 8.67 (d, J = 4.6 Hz,
2 H, β-pyrrole), 8.68 (d, J = 4.6 Hz,
2 H, β-pyrrole), 8.93 (s, 2 H, β-pyrrole),
9.75 (s, 2 H, β-thiophene). ¹³C
NMR (100 MHz, CDCl3): δ = 21.8, 31.2,
103.2, 120.9, 121.3, 123.6, 128.4, 128.5, 129.2, 130.4, 133.2, 134.3, 134.7,
135.2, 135.9, 136.9, 138.1, 138.4, 145.8, 148.3, 154.1, 156.8, 157.1,
157.6. ES-MS: m/z calcd for C52H44BN3O2S:
785.3; found: 786.4 (100%) [M + 1]+.
Anal. Calcd for C52H44BN3O2S:
C, 79.48; H, 5.64; N, 5.35. Found: C, 79.53; H, 5.68; N, 5.30.
Porphyrin 2: Porphyrin 2 was
synthesized in 58% yield following same experimental conditions
used for the synthesis of porphyrin 1. ¹H
NMR (400 MHz, CDCl3): δ = 1.16 (s,
6 H, CH3), 2.70 (s, 9 H, CH3), 3.96 (s, 4
H, CH2), 7.21 (d, J = 7.6
Hz, 2 H, ArH), 7.61 (d, J = 7.6
Hz, 6 H, ArH), 8.08 (d, J = 7.6
Hz, 6 H, ArH), 8.23 (s, 2 H, ArH), 8.67 (s, 4 H, β-pyrrole),
9.95 (s, 4 H, β-thiophene). ¹³C
NMR (100 MHz, CDCl3): δ = 22.6, 22.8,
31.1, 31.5, 128.0, 129.5, 133.6, 134.7, 134.9, 135.1, 135.7, 136.1,
138.0, 146.8, 147.6, 148.5, 148.7, 149.8, 150.9, 155.1, 157.1. MALDI-TOF: m/z calcd
for C52H43BN2O2S2:
802.3; found: 802.1 (100%) [M]+.
Anal. Calcd for C52H43BN2O2S2:
C, 77.79; H, 5.40; N, 3.49. Found: C, 77.85; H, 5.38; N, 3.52.
General
procedure for dyads 13 and 14: Samples of meso-bromo
N3S porphyrin 10/β-bromo
ZnN4 porphyrin 15 and N2S2 porphyrin
boronic ester 2 or N2S2 porphyrin
boronic acid 7 were
dissolved in anhydrous toluene-triethylamine (6 mL, 5:1)
in a 25-mL two-necked, round-bottomed flask under a nitrogen atmosphere.
Cs2CO3 (1.5 equiv) followed by Pd(PPh3)4 (0.1
equiv) were added and the resulting mixture was heated at 80 ˚C
for 4 h. After work-up, the crude compound was subjected to silica
gel chromatography to afford dyads 13 and 14 as purple solids in reasonable yields.
Spectral
data for compounds 13 and 14:
Compound 13: Yield: 78%. ¹H
NMR (400 MHz, CDCl3):
δ = -2.55 (s, 1 H, NH), 2.64 (t, J = 7.9 Hz,
18 H, CH3), 7.47 (d, J = 7.6
Hz, 2 H, ArH), 7.50-7.54 (m, 10 H, ArH), 7.58 (d, J = 7.6 Hz,
2 H, ArH), 7.99 (d, J = 7.9
Hz, 2 H, ArH), 8.03-8.12 (m, 12 H, ArH), 8.52 (d, J = 4.6 Hz,
1 H, β-pyrrole), 8.59 (s, 2 H, β-pyrrole),
8.61-8.62 (m, 2 H, β-pyrrole),
8.64 (d, J = 4.6
Hz, 1 H, β-pyrrole), 8.70 (d, J = 4.3 Hz,
1 H,
β-pyrrole), 8.87
(dd, J = 10.7,
2.1 Hz, 2 H, β-pyrrole), 9.19 (d, J = 4.6 Hz,
1 H, β-pyrrole), 9.59 (s, 2 H, β-thiophene), 9.63
(d, J = 4.9 Hz, 1 H, β-thiophene),
9.69 (d, J = 5.2 Hz, 1 H, β-thiophene),
9.79 (d, J = 5.2 Hz, 1 H, β-thiophene), 10.22
(d, J = 5.2 Hz, 1 H, β-thiophene). ¹³C
NMR (100 MHz, CDCl3): δ = 21.7, 22.9,
34.0, 53.6, 114.3, 115.1, 121.3, 127.5, 128.6, 129.3, 131.9, 132.0,
134.4, 134.8, 135.8, 137.2, 140.1, 146.5, 148.9, 150.5, 150.9, 154.9. MALDI-TOF: m/z calcd
for C88H63N5S3: 1285.4;
found: 1285.6 (100%) [M]+.
Anal. Calcd for C88H63N5S3:
C, 82.15; H, 4.94; N, 5.44. Found: C, 82.21; H, 4.85; N, 5.41.
Compound 14: Yield: 58%. ¹H
NMR (400 MHz, CDCl3):
δ = 2.63
(s, 21 H, CH3), 7.35-7.39 (m, 4 H, ArH), 7.52-7.54 (m,
8 H, ArH), 7.62 (d, J = 7.7
Hz, 6 H, ArH), 7.69-7.71 (m, 6 H, ArH), 7.93 (d, J = 7.0
Hz, 2 H, ArH), 8.05 (d, J = 7.0 Hz, 2 H, ArH), 8.13 (d, J = 7.4 Hz,
4 H, ArH), 8.32 (d, J = 4.0
Hz, 2 H, β-pyrrole), 8.69-8.71
(m, 4 H, β-pyrrole), 8.74-8.76
(m, 2 H, β-pyrrole), 8.84 (s,
1 H, β-pyrrole), 9.42 (s, 1 H, β-pyrrole),
9.54 (s, 1 H, β-pyrrole), 9.70
(s, 2 H, β-thiophene), 9.73 (d, J = 5.2 Hz,
2 H, β-thiophene). ¹³C
NMR (100 MHz, CDCl3): δ = 23.7, 110.8,
114.8, 118.2, 126.3, 128.5, 128.3, 129.0, 129.4, 130.6, 131.0, 132.0,
132.7, 133.6, 134.4, 135.2, 135.7, 136.3, 137.0, 137.6, 141.3, 143.1,
146.3, 155.5. MALDI-TOF: m/z calcd for C96H70N6S2Zn:
1434.4; found: 1434.5 (100%) [M]+.
Anal. Calcd for C96H70N6S2Zn:
C, 80.23; H, 4.91; N, 5.85. Found: C, 80.15; H, 5.01; N, 5.78.