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Synlett 2005(14): 2199-2203  
DOI: 10.1055/s-2005-872245
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Functionalized Unsymmetrical Thiophene Diols and Their Use in the Synthesis of cis-21-Monothia- and cis-21,23-Dithiaporphyrin Building Blocks with Two Different Functional Groups

Sokkalingam Punidha, Mangalampalli Ravikanth*
Department of Chemistry, Indian Institute of Technology, Powai, Mumbai 400076, India
Fax: +91(22)25767152; e-Mail: ravikanth@chem.iitb.ac.in;
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Publication History

Received 16 May 2005
Publication Date:
26 July 2005 (online)

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Abstract

A series of functionalized unsymmetrical thiophene ­diols were synthesized and used for the synthesis of cis-21-monothia and cis-21,23-dithiaporphyrin building blocks having two ­different functional groups at meso-positions. To show the use of the cis-thiaporphyrin building blocks with two different functional groups, a porphyrin trimer comprised of N4, N3S and N2S2 por­phyrin sub-units was synthesized by using both covalent and non-covalent interactions.

Key words

functionalized unsymmetrical diols - cis-thiaporphyrin - porphyrin trimer - covalent - non-covalent interactions

5

Experimental Procedure and Spectroscopic Data for Selected Compounds. Diol 9: the thiophene mono-ol 3 (1.00 g, 3.67 mmol), tetramethylethylenediamine (1.39 mL, 9.18 mmol) and n-BuLi (5.74 mL of ca. 15% solution in hexane) were added successively to freshly distilled dry Et2O (30 mL) in a 250-mL three-necked round-bottomed flask and stirred for 15 min under nitrogen atmosphere at 0 °C. An ice-cold solution of 4-pyridine carboxaldehyde (0.87 mL, 9.18 mmol) in dry THF (30 mL) was added to it. The mixture was stirred for 15 min and ice-cold NH4Cl (50 mL, ca. 1 M) was added to quench the reaction. After standard work up, the crude compound was purified by silica gel column chromatography using CH2Cl2-MeOH (95:5) and diol 4 obtained as a yellow oily liquid (0.40 g, 29%). 1H NMR (400 MHz, CDCl3): δ = 0.92 (6 H, s, CH3), 4.00 (3 H, br s, OH), 5.99-6.15 (2 H, m, CHOH), 6.82-6.86 (2 H, m, thiophene), 7.42-7.44 (2 H, m, aryl), 7.70 (2 H, d, J = 7.8 Hz, pyridyl), 8.03-8.06 (2 H, m, aryl), 8.30 (2 H, br s, pyridyl) ppm. ES-MS: m/z calcd for C22H21NO3S: 379.48; found: 378.09 (100%) [M+ - H]. Anal. Calcd: C, 69.63; H, 5.58; N, 3.69. Found: C, 69.74; H, 5.51; N, 3.74.
Porphyrin 15: condensation of diol 9 (0.45 g, 1.19 mmol) with 10 (0.50 g, 1.19 mmol) in propionic acid (125 mL) at refluxing temperature for 2 h followed by standard work up and chromatography on silica using CH2Cl2-MeOH (96:4) gave the desired porphyrin 15 as a purple solid (0.07 g, 8%). 1H NMR (400 MHz, CDCl3): δ = 0.94 (6 H, s, CH3), 2.69 (6 H, s, CH3), 7.52 (2 H, d, J = 7.8 Hz, aryl), 7.62 (4 H, d, J = 8.0 Hz, aryl), 7.98 (2 H, d, J = 7.8 Hz, aryl), 8.11 (4 H, d, J = 8.0 Hz, aryl), 8.20 (2 H, d, J = 7.8 Hz, 3,5-pyridyl), 8.54 (1 H, m, β-pyrrole), 8.64 (1 H, d, J = 4.6 Hz, β-pyrrole), 8.72 (1 H, d, J = 4.6 Hz, β-pyrrole), 8.78-8.81 (1 H, m, β-pyrrole), 9.14 (2 H, br s, 2,6-pyridyl), 9.54 (1 H, d, J = 4.4 Hz, β-thiophene), 9.72 (1 H, d, J = 4.4 Hz, β-thiophene), 9.76 (2 H, s, β-thiophene) ppm. 13C NMR (100 MHz, CDCl3): δ = 22.56, 22.68, 31.06, 31.49, 128.03, 129.49, 133.61, 134.71, 134.93, 135.14, 135.73, 136.13, 138.02, 146.90, 147.61, 148.53, 148.68, 149.75, 150.87, 155.11, 156.63, 157.01 ppm. ES-MS: m/z calcd for C50H37N3OS2: 759.96; found: 760.31 (100%) [M+]. UV/Vis (in toluene, λmax/nm, ε/mol-1 dm3 cm-1): 437 (292652), 515 (26193), 549 (9062), 634 (2073), 697 (5030).
Porphyrin 16: sample of porphyrin 15 (0.05 g, 0.07 mmol) was dissolved in benzene-MeOH (3:1, 40 mL) taken in a 100-mL round-bottomed flask and excess KOH (0.20 g) was added to it. The reaction mixture was refluxed at 80 °C using a Dean-Stark apparatus. The excess solvent was removed under vacuum and the crude compound was subjected to silica gel column chromatography using PE-CH2Cl2 (5:95) to afford the pure desired porphyrin 16 as a purple solid (0.04 g, 88%). 1H NMR (400 MHz, CDCl3): δ = 2.70 (6 H, s, CH3), 3.32 (1 H, s, CH), 7.50 (2 H, d, J = 7.8 Hz, aryl), 7.62 (4 H, d, J = 8.0 Hz, aryl), 7.96 (2 H, d, J = 7.8 Hz, aryl), 8.14 (4 H, d, J = 8.0 Hz, aryl), 8.20 (2 H, d, J = 7.8 Hz, 3,5-pyridyl), 8.56 (1 H, d, J = 4.5 Hz, β-pyrrole), 8.64 (1 H, d, J = 4.6 Hz, β-pyrrole), 8.72 (1 H, d, J = 4.6 Hz, β-pyrrole), 8.80 (1 H, d, J = 4.5 Hz, β-pyrrole), 9.11 (2 H, br s, 2,6-pyridyl), 9.58 (1 H, d, J = 4.4 Hz, β-thiophene), 9.68 (1 H, d, J = 4.4 Hz, β-thiophene), 9.76 (2 H, s, β-thiophene) ppm. 13C NMR (100 MHz, CDCl3) δ = 21.61, 31.07, 31.49, 121.95, 128.31, 131.29, 132.54, 134.18, 134.55, 134.92, 135.75, 135.93, 138.32, 141.98, 147.52, 147.80, 148.92, 150.98, 155.95, 156.54, 156.60, 160.02 ppm. ES-MS: m/z calcd for C47H31N3S2: 701.90; found: 702.22 (100%) [M+]. UV/Vis (in toluene, λmax/nm, ε/mol-1 dm3 cm-1): 436 (262893), 515 (24005), 549 (8393), 634 (1845), 697 (4601).
Dimer 18: A solution of 16 (0.02 g, 0.03 mmol) and 17 (0.02 g, 0.03 mmol) in dry toluene-Et3N (3:1, 30 mL) was purged with nitrogen for 10 min. The coupling was initiated by adding AsPh3 (0.01 g, 0.03 mmol) followed by Pd2(dba)3 (0.01 g, 0.01 mmol) and the reaction mixture was then stirred at 40 °C for 12 h. After work-up, the crude compound was subjected to silica gel column chromatography and the desired dimer 18 was collected with PE-CH2Cl2 (15:85) mixture as a violet solid (0.02 g, 64%). 1H NMR (400 MHz, CDCl3): δ = -2.71 (1 H, br s, NH), 2.70 (9 H, s, CH3), 2.73 (6 H, s, CH3), 7.53 (4 H, d, J = 7.6 Hz, aryl), 7.61 (8 H, d, J = 7.6 Hz, aryl), 7.96 (2 H, d, J = 8.0 Hz, aryl), 8.06 (4 H, d, J = 7.6 Hz, aryl), 8.12 (10 H, m, aryl), 8.17 (2 H, m, 3,5-pyridyl), 8.62 (4 H, m, β-pyrrole), 8.68 (3 H, m, β-pyrrole), 8.73 (1 H, d, J = 5.6 Hz, β-pyrrole), 8.94 (2 H, m, β-pyrrole), 9.03 (2 H, br m, 2,6-pyridyl), 9.58 (1 H, d, J = 5.2 Hz, β-thiophene), 9.67 (1 H, d, J = 5.2 Hz, β-thiophene), 9.72 (3 H, m, β-thiophene), 9.76 (1 H, d, J = 5.2 Hz, β-thiophene) ppm. ES-MS: m/z calcd for C94H63N6S3: 1373.76; found: 1373.57 (52%) [M+]. UV/Vis (in toluene, λmax/nm, ε/mol-1 dm3 cm-1): 433 (484803), 515 (41725), 549 (13604), 624 (3694), 680 (5357), 696 (4918).
Trimer 20: The dimer 18 (0.02 g, 0.02 mmol) was dissolved in 30 mL of toluene in a two-necked 100-mL round-bottomed flask and was purged with N2 for 10 min. RuTPP(CO)(EtOH) (19; 0.019 g, 0.02 mmol) was then added and the solution was refluxed with stirring for 4 h. The crude compound was purified by silica gel column chromatography using PE-CH2Cl2 (50:50) mixture as an eluent and afforded trimer 20 as a purple solid (0.01 g, 35%). 1H NMR (400 MHz, CDCl3): δ = -2.61 (1 H, br s, NH), 1.64 (2 H, d, J = 3.2 Hz, 2,6-pyridyl), 2.68 (6 H, s, CH3), 2.70 (9 H, s, CH3), 6.08 (2 H, d, J = 3.2 Hz, 3,5-pyridyl), 7.10 (1 H, d, J = 4.4 Hz, β-pyrrole), 7.56 (18 H, m, aryl), 7.63 (4 H, d, J = 7.8 Hz, aryl), 7.71 (10 H, m, aryl), 7.91 (4 H, t, J = 7.4 Hz, aryl), 8.04 (8 H, m, aryl), 8.14 (4 H, d, J = 7.8 Hz, aryl), 8.19 (1 H, m, β-pyrrole), 8.33 (1 H, m, β-thiophene), 8.57 (2 H, m, β-pyrrole), 8.63 (2 H, m, β-pyrrole), 8.74 (8 H, s, β-pyrrole of TPP), 8.90 (4 H, m, β-pyrrole), 9.29 (2 H, m, β-thiophene), 9.57 (1 H, dd, J = 5.2 Hz, β-thiophene), 9.83 (2 H, m, β-thiophene) ppm. ES-MS: m/z calcd for C139H92N10OS3Ru: 2115.57; found: 2115.79 (23%). UV/Vis (in toluene, λmax/nm, ε/mol-1 dm3 cm-1): 412 (302417), 432 (527038), 516 (35230), 549 (17975), 626 (bs), 683 (6228), 698 (5204).