Cis / trans -isomerizations in 1,2-bis(2-thienyl)ethene derivatives: a joint experimental and computational approach

Formylation, Dicyanovinylation and Tricyanovinylation of 5‐Alkoxy‐ and 5‐Amino‐Substituted 2,2′‐Bithiophenes.

“…The formylation of thiophene and oligothiophene derivatives is usually achieved by two methods: through the Vilsmeier reaction, [18][19][20][21] (or by a modified procedure of the Vilsmeier formylation using DMF/POCl 3 in dichloroethane [22][23][24] or by metalation followed by formyldelithiation using DMF. 7,21,[25][26][27] Meth-Cohn et al 19 have recently published a study of the regioselective electrophilic Vilsmeier formylation of 3substituted thiophenes which clearly evidences the effect of the increasing size of the Vilsmeier reagent. They showed that the regioselective Vilsmeier formylation of 3substituted thiophenes may be optimized with either small (obtention of the 2-isomer) or large planar aromatic Vilsmeier reagents (obtention of the 5-isomer).…”

Molecular and crystal properties of E-1,2-bis(3-methoxy-2-thienyl)ethene: static disorder in the crystal

“…The title compound was synthesized as previously reported (Blockhuys et al, 1999) and single crystals were grown by the slow evaporation of solvent from a saturated solution in petroleum ether.…”

“…The geometries of the three planar conformers of E-1,2bis(3-methoxy-2-thienyl)ethane ( Fig. 1) were calculated previously at the Hartree±Fock level (Blockhuys et al, 1999). For this study full geometry optimizations were additionally performed for all conformers using Gaussian98 (Frisch et al, 1998) at the DFT/B3LYP level of theory using the 6-31G* and 6±311+G* basis sets; these were used as they are implemented in the program.…”

“…Intuitively, as well as on the basis of the level of theory and the size of the basis set used, one expects the latter situation to be true. It has been suggested that in conformer (1a) two intramolecular hydrogen interactions exist between an H atom of the ethenediyl spacer and the O atom of the methoxy group in a stable ®ve-membered ring con®guration, designated CHÐ n(O) (Blockhuys et al, 1999). On going from conformer (1a) to (1b) only one of these interactions needs to be broken, while both are broken on going from (1a) to (1c).…”

“…As part of our continuing research into the semiconductor applications of arylene vinylene oligomers (Tachelet et al, 1994;Vanneste et al, 1998;Poels et al, 1998;De Wit et al, 1998), we have synthesized various substituted 1,2-bis(2-thienyl)ethenes (Blockhuys et al, 1999) in order to assess the in¯uence of the pattern of substitution on the compounds' properties, amongst which are solubility and electrical conductivity. UV and electron spin resonance (ESR) spectroscopy indicate that the electronic properties of poly-(thiophenes) and other poly(heterocycles) are dictated by the carbon backbone alone and that the role of the heteroatom is subordinate (Ford et al, 1982;Tourillon, 1986).…”