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Synlett 2009(16): 2583-2588  
DOI: 10.1055/s-0029-1217952
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Thieme Chemistry Journal Awardees - Where Are They Now? [3]-Cumulenes, Sulfanyl-Substituted Butadienes, and Functionalized Thiophenes Starting from Polypyridinium Salts

Alireza Rahimia, Mimoza Gjikajb, Andreas Schmidt*a
a Institute of Organic Chemistry, Clausthal University of Technology, Leibnizstr. 6, 38678 Clausthal-Zellerfeld, Germany
Fax: +49(5323)723861; e-Mail: schmidt@ioc.tu-clausthal.de;
b Institute of Inorganic Chemistry, Clausthal University of Technology, Paul-Ernst-Str. 4, 38678 Clausthal-Zellerfeld, Germany
Further Information

Publication History

Received 24 July 2009
Publication Date:
04 September 2009 (online)

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Abstract

Hexachlorobuta-1,3-diene reacted with DMAP, 4-(pyrrolidin-1-yl)pyridine, 4-(morpholin-1-yl)pyridine, and 4-amino­pyridine to 1,1′,1′′,1′′′-tetrakis-(2,3-dichlorobuta-1,3-diene-1,1,4,4-tetrayl)pyridinium salts, respectively. Except for the 4-amino derivative, these salts were converted into 1,1′-bis-(1,2,3,4-tetrachloro-buta-1,3-diene-1,4-diyl)pyridinium salts on treatment with bromine or iodine in acetic acid or water. On reaction with thiolates, tetrakis-sulfanyl-substituted [3]-cumulenes were obtained, whereas treatment with sulfur yielded 1,1′-bis-(2,3-dichloro-thiophene-1,4-diyl)pyridinium salts. Sodium disulfide gave 1,1′-bis-(2,3-dichloro-1,4-dimercaptobuta-1,3-diene-1,4-diyl)pyridinium salts.

Key words

DMAP - polycations - substitution

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General Procedure for the Synthesis of the Tetracationic Salts 16a-d Hexachlorobuta-1,3-diene (10b, 4 mmol, 1.04 g) was dissolved in the solvent specified in Table  [¹] and then 20 mmol of the corresponding heteroaromatic nucleophiles were added. The mixture was then stirred at the temperature presented in Table  [¹] . The resulting precipitate was collected by filtration and washed subsequently with EtOAc. Finally, this solid was recrystallized from MeCN-MeOH (95:5). Thus, for the synthesis of 16c 3.28 g of 4-(morpholin-1-yl)pyridine were used. Decomposition of 16c >208 ˚C. ¹H NMR (400 MHz, D2O): δ = 8.18 (d, J = 7.8 Hz, 4 H, α-H), 8.10 (d, J = 7.8 Hz, 4 H, α′-H), 7.31 (d, J = 7.8 Hz, 4 H, β-H), 7.23 (d, J = 7.8 Hz, 4 H, β′-H), 3.92 (s, 16 H), 3.91 (s, 16 H). ¹³C NMR (100 MHz, D2O): δ = 156.6, 155.5, 140.5, 140.3, 137.8, 120.2, 109.6, 108.7, 65.7, 65.6, 47.7, 47.6.
IR (KBr): 3417, 3071, 1639, 1565, 1431, 1107, 1038, 824
cm-¹. ESI-MS: m/z = 881 [M4+ + 3 Cl-], 193.6 [M4+/4]. Anal. Calcd (%) for C40H48Cl6N8O4˙9 H2O: C, 44.50; H, 6.12; N, 10.40. Found: C, 44.46; H, 5.62; N, 10.56.

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General Procedure for the Reaction of 16a-d with Halogens to 17a-d The salts 16a-d (0.25 mmol) were dissolved in AcOH or H2O (20 mL), then bromine (0.5 mmol) or iodine (0.5 mmol) was added. The precipitate was collected, filtered, and washed with H2O. The reaction in AcOH afforded recrystallization.
Synthesis of 17a
After 5 min of stirring the reaction mixture containing bromine in AcOH at r.t. was filtered, and the resulting solid was washed. After crystallization in 2-PrOH-MeCN (1:2) orange crystals were obtained, mp 234-236 ˚C. ¹H NMR (400 MHz, DMSO): δ = 8.54 (d, J = 7.8 Hz, 4 H, α-H), 7.26 (d, J = 7.8 Hz, 4 H, β-H), 3.35 (s, 12 H). ¹³C NMR (100 MHz, DMSO): δ = 156.4, 140.5, 131.2, 123.1, 108.6, 40.7. IR (KBr): 3091, 3054, 1646, 1580, 1340, 1179, 815 cm-¹. ESI-MS: m/z = 512.5 [M²+ + Br-], 217 [M²+/2]. Anal. Calcd (%) for C18H20Br2Cl4N4˙H2O: C, 35.32; H, 3.62; N, 9.15. Found: C, 35.43; H, 3.41; N, 9.37.

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X-ray Structure Analysis for C 18 H 22 Br 2 Cl 4 N 4 O A suitable single crystal of the title compound was selected under a polarization microscope and mounted in a glass capillary (d = 0.3 mm). The crystal structure was determined by X-ray diffraction analysis using graphite monochromated Mo Kα radiation [0.71073 Å; T = 223 (2) K], whereas the scattering intensities were collected with a single crystal diffractometer (STOE IPDS II). The crystal structure was solved by direct methods using SHELXS-97 and refined using alternating cycles of least-squares refinements against F ² (SHELXL-97).³¹ All non-H atoms were located in difference Fourier maps and were refined with anisotropic displacement parameters. The H positions were determined by a final difference Fourier synthesis. C18H22Br2Cl4N4O (M = 612.00 g mol-¹) crystallized in the monoclinic space group P21/n (no. 14), lattice parameters a = 10.188 (2) Å, b = 16.462 (2) Å, c = 18.298 (2) Å, β = 104.88 (1)˚, V = 2966.1 (6) ų, Z = 4, d calc  = 1.370 g cm-³, F(000) = 1280 using 5433 independent reflections and 405 parameters. R1 = 0.0609, wR2 = 0.1268 [I > 2σ(I)], goodness of fit on F ²  = 1.103, residual electron density = 0.854 and -0.671 e Å-³. Further details of the crystal structure investigations have been deposited with the Cambridge Crystallographic Data Center, CCDC 739729. Copies of this information may be obtained free of charge from The Director, CCDC,
12 Union Road, Cambridge, CB2 1EZ, UK [fax: +44 (1223)336033; e-mail: fileserv@ccdc.ac.uk or
http://www.ccdc.cam.ac.uk].

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General Procedure for the Synthesis of Thiophenes 19a-c In a sealed tube of 16a-c (0.25 mmol) and sulfur (0.5 mmol) in DMF (15 mL) were reacted at reflux temperature for 3 h. The dark brown solution was poured into Et2O (150 mL). The resulting precipitate was filtered off and washed with Et2O.
Anion Exchange to Hexafluorophosphate
To a stirred solution of 19a 2Cl- (0.5 mmol, 0.233 g) in H2O (10 mL) was added NaPF6 (1.5 mmol, 0.252 g) in H2O (10 mL). After 5 min of stirring, the resulting precipitate was filtered off and dried in vacuo. Finally, a light brown solid was obtained, mp 222-224 ˚C. ¹H NMR (200 MHz, acetone-d 6): δ = 8.33 (d, J = 7.8 Hz, 4 H, α-H), 7.34 (d, J = 7.8 Hz, 4 H, β-H), 3.48 (s, 12 H). ¹³C NMR (50 MHz, acetone-d 6): δ = 158.7, 144.3, 136.3, 123.5, 109.9, 41.8. IR (KBr): 3182, 2946, 1650, 1562, 1408, 1262, 840 cm-¹. Anal. Calcd (%) for C18H20Cl2F12N2P2S: C, 31.55; H, 2.94; N, 8.18. Found: C, 31.43; H, 2.73; N, 8.46.

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General Procedure for the Reaction of 16a-d with Sodium Disulfide to 20a-c Sodium disulfide was prepared by refluxing of sodium sulfide (0.5 mmol) with sulfur (0.5 mmol) in dry MeCN (15 mL) at reflux temperature for 15 min. After this period of time a dark blue solution was obtained. The salts 16a-c and three drops of MeOH were then added, respectively. The reaction mixture was then heated at reflux temperature for additional 3 h. After cooling, EtOAc (30 mL) was added. The resulting precipitate was filtered off and washed with EtOAc. Crystallization in MeCN-2-PrOH gave the corresponding compounds 20a-c. Compound 20a was obtained as a yellow solid, mp 232-233 (dec.). ¹H NMR (200 MHz, D2O): δ = 8.19 (d, J = 7.8 Hz, 4 H, α-H), 7.06 (d, J = 7.8 Hz, 4 H, β-H), 3.33 (s, 12 H). ¹³C NMR (50 MHz, D2O): δ = 157.1, 140.0, 131.2, 123.3, 108.0, 40.2. IR (KBr): 3036, 2647, 1652, 1574, 1576, 1408, 1345, 1204, 816 cm-¹. ESI-MS: m/z = 214 [M²+/2]. Anal. Calcd (%) for C18H22Cl2N4S3˙4 H2O: C, 40.52; H, 5.67; N, 10.50. Found: C, 40.26; H, 5.33; N, 11.08.

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X-ray Structure Analysis for Compound 20a A crystal of the title compound was selected under a polarization microscope and mounted in a glass capillary (d = 0.3 mm). The crystal structure was determined by X-ray diffraction analysis using graphite monochromated Mo Kα radiation [0.71073 Å, T = 223 (2) K], whereas the scattering intensities were collected with a single crystal diffractometer (STOE IPDS II). The crystal structure was solved by Direct Methods using SHELXS-97. ³¹ Despite of intense efforts, the quality of the crystal was insufficient, so that the H atoms could not be localized.