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Synlett 2008(1): 41-44  
DOI: 10.1055/s-2007-1000836
LETTER
© Georg Thieme Verlag Stuttgart · New York

A New Stereoselective Approach to (E)-Poly(arylenevinylene)s

Wiesaw Prukała, Piotr Pawluć , Krystian Posaa, Bogdan Marciniec*
Department of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland
Fax: +48(61)8291508; e-Mail: marcinb@amu.edu.pl;
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Publication History

Received 16 October 2007
Publication Date:
11 December 2007 (online)

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Abstract

A new synthetic protocol for the one-pot, stereoselective synthesis of (E)-poly(arylenevinylene)s via palladium-catalyzed Hiyama cross-coupling of dihaloarenes with cyclic gem-bis(silyl)ethene or isopropoxydimethylvinylsilane is described.

Key words

poly(arylenevinylene)s - cross-coupling - palladium catalyst - organometallic reagents - silicon derivatives

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Reaction of Cyclic 1,1-Bis(silyl)ethene (1) with Aryl IodidesThe glass reactor (100 mL, two-necked, round-bottomed flask equipped with a magnetic stirring bar, reflux condenser, argon bubbling tube and thermostated heating oil bath) was evacuated and flushed with argon. Compound 1 (1 g, 4.95 mmol) and anhyd THF (20 mL) were added to the reactor. At r.t. 14.8 mmol of TBAF (1 M soln in THF) was added and the mixture was stirred for 10 min. After this time, 9.9 mmol of the respective aryl iodide and 56.8 mg (9 µmol) of Pd2(dba)3 were added and the reaction mixture was stirred under argon for 2 h at 65 °C. After the reaction was completed (GC-MS analysis) the volatiles were evaporated under vacuum and the crude product was chromatographed on silica gel (eluent: hexane-EtOAc, 10:1) to afford the analytically pure products. Isolated yields: (E)-stilbene, 96%; (E)-4,4′-dimethoxystilbene, 92%.

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Synthesis of PAV from Cyclic 1,1-Bis(silyl)ethene (1)[Pd2(dba)3] (9.16 mg, 0.01 mmol), dioxane (4 mL), 2,2,4,4-tetramethyl-3-methylene-1,5-dioxa-2,4-disilacycloheptane (1, 202 mg, 1 mmol), TBAF (640 mg, 2.4 mmol), and respective dihaloarene (0.9 mmol) were placed in an evacuated and flushed with argon 25 mL flask. The mixture was heated at 80 °C for 16-48 h under an argon atmosphere. The degree of conversion of the substrates was estimated by GC and TLC analyses. Then, the reaction mixture was cooled and the precipitated solid was filtered and washed extensively with acetone. The final product was separated using filtration (2, 6) or chromatography column (3-5, 7) with silica (THF-EtOAc). The desired products were obtained by combining both fractions of solids to afford the desired polymeric products.

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One-Pot Synthesis of PAV from Isopropoxydimethyl­-vinylsilaneThe glass minireactor (10 mL, equipped with a magnetic stirring bar, argon bubbling tube and thermostated heating oil bath) was evacuated and flushed with argon. Then, [RuH(Cl)(CO)(PPh3)3] (19.05 mg, 0.02 mmol), CuCl (1.98 mg, 0.02 mmol), isopropoxydimethylvinylsilane (0.144 g, 1.0 mmol), and anhyd dioxane (1.0 mL) were added to the reactor (in the case of reaction with 4,4′diiodobiphenyl and 2,5-diiodothiophene 2 mL of dioxane). The reaction mixture was heated at 110 °C for 16 h under an argon flow. After the reaction was completed [GC-MS and 1H NMR analyses confirmed the formation of the mixture of (E)-1,2-bis(iso-propoxydimethylsilyl)ethene A and 1,1-bis(isopropoxy-dimethylsilyl)ethene B], palladium catalyst [Pd2(dba)3] (0.005 mmol), TBAF (1 M solution in THF, 320 mg, 1.2 mmol), and respective dihaloarene (0.45 mmol) were added and the mixture was heated at 80 °C for 16-48 h under an argon atmosphere. The degree of conversion of the substrates was estimated by GC and TLC analyses. Then, the reaction mixture was cooled and the precipitated solid was filtered and washed extensively with acetone. The final product was separated using filtration (2, 6) or chromatography column (3-5, 7) with silica (THF-EtOAc). The desired products were obtained by combining both fractions of solids to afford the desired polymeric product.

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Spectroscopic Data of the Selected Products( E )-Poly(1,4-phenylenevinylene)s (2)IR (KBr): 740.5 (s), 834.8 (s), 964.7 (s), 1015.2 (s), 1256.0, 1488.6, 1512.8, 1596.6, 1695.9 (s, br), 2922.6, 2953.9, 3021.6 (s) cm-1. 1H NMR (300 MHz, DMSO-d 6): δ = 0.15 (s, SiCH3), 0.21 (s, SiCH3), 6.50 (d, J = 19.2 Hz, PhCH=), 6.94 (d, J = 19.2 Hz, PhCH=), 7.41 (d, J = 8.5 Hz, H in phenyl ring), 7.54 (d, J = 8.5 Hz, H in phenyl ring) ppm. 13C NMR (75 MHz, DMSO-d 6): δ = 0.1, 0.5, 0.8, 29.0, 31.3, 128.2, 128.7, 129.2, 132.4 ppm. Anal. Calcd for (C8H6)n: C, 94.07; H, 5.92. Found: C, 91.58; H, 5.43.( E )-Poly(2,3,5,6-tetrafluorophenylenevinylene)s (5)IR (KBr): 758.7 (s), 938.6, 979.5, 1091.1 (s, br), 1215.7, 1486.4, 1527.7, 1617.3, 1652.9, 2928.8, 2961.1, 3019.3 (s) cm-1. 1H NMR (300 MHz, CDCl3): δ = 0.10 (s, SiCH3), 0.20 (s, SiCH3), 7.09 (d, J = 16 Hz, PhCH=), 7.75 (d, J = 16 Hz, PhCH=) ppm. 13C NMR (75 MHz, CDCl3): δ = -0.2, 0.6, 29.4, 29.7, 30.3, 125.4, 128.4, 128.9, 130.5, 143.4 ppm. Anal. Calcd for (C8F4H2)n: C, 55.19; H, 1.19. Found: C, 55.37; H, 1.43.( E )-Poly(2,5-thiophenylenevinylene)s (7)IR (KBr): 790.6 (s, br), 935.8, 1039.4 (s, br), 1070.1, 1258.5, 1444.5, 1618.6, 1655.2, 1722.2, 2924.3, 2957.4, 3065.4 cm-1. 1H NMR (300 MHz, CDCl3): δ = 0.08 (s, SiCH3), 0.20 (s, SiCH3), 6.40-7.80 (m, H in thiophenyl ring and ArCH=) ppm. 13C NMR (75 MHz, CDCl3): δ = 0.1, 0.9, 14.2, 19.6, 23.1, 29.8, 30.4, 124.2, 125.4, 128.3, 128.7, 128.8, 130.4, 130.8, 143.2 ppm. Anal. Calcd for (C6H4S)n: C, 66.62; H, 3.72; S, 29.64. Found: C, 62.58; H, 3.03; S, 28.33.