Selectivity of Br/Li Exchange and Deprotonation of 4,4′-Dibromo-3,3′-bithiophene for Synthesis of Symmetrical and Unsymmetrical Dithienoheteroaromatic Rings

The novel selective synthesis of symmetrical and unsymmetrical dithienoheteroaromatic rings (<b>DTHA</b>s) has been developed via intramolecular cyclization of 4,4′-dibromo-3,3′-bithiophene (<b>3</b>). Four reaction conditions including <i>n</i>-BuLi/Et₂O, <i>n</i>-BuLi/THF, <i>s</i>-BuLi/Et₂O, and <i>t</i>-BuLi/Et₂O were employed to react with <b>3</b> for selective formation of two types of dicarbanions, which generate the symmetrical and unsymmetrical <b>DTHA</b>s after quenching with three electrophilic reagents (<b>4a</b>–<b>c</b>). The possible mechanism of formation of <b>DTHA</b>s was proposed. In addition, two unsymmetrical <b>DTHA</b>s were confirmed by X-ray single-crystal analyses

Selectivity of Br/Li Exchange and Deprotonation of 4,4′-Dibromo-3,3′-bithiophene for Synthesis of Symmetrical and Unsymmetrical Dithienoheteroaromatic Rings

The novel selective synthesis of symmetrical and unsymmetrical dithienoheteroaromatic rings (<b>DTHA</b>s) has been developed via intramolecular cyclization of 4,4′-dibromo-3,3′-bithiophene (<b>3</b>). Four reaction conditions including <i>n</i>-BuLi/Et₂O, <i>n</i>-BuLi/THF, <i>s</i>-BuLi/Et₂O, and <i>t</i>-BuLi/Et₂O were employed to react with <b>3</b> for selective formation of two types of dicarbanions, which generate the symmetrical and unsymmetrical <b>DTHA</b>s after quenching with three electrophilic reagents (<b>4a</b>–<b>c</b>). The possible mechanism of formation of <b>DTHA</b>s was proposed. In addition, two unsymmetrical <b>DTHA</b>s were confirmed by X-ray single-crystal analyses

Selectivity of Br/Li Exchange and Deprotonation of 4,4′-Dibromo-3,3′-bithiophene for Synthesis of Symmetrical and Unsymmetrical Dithienoheteroaromatic Rings

The novel selective synthesis of symmetrical and unsymmetrical dithienoheteroaromatic rings (<b>DTHA</b>s) has been developed via intramolecular cyclization of 4,4′-dibromo-3,3′-bithiophene (<b>3</b>). Four reaction conditions including <i>n</i>-BuLi/Et₂O, <i>n</i>-BuLi/THF, <i>s</i>-BuLi/Et₂O, and <i>t</i>-BuLi/Et₂O were employed to react with <b>3</b> for selective formation of two types of dicarbanions, which generate the symmetrical and unsymmetrical <b>DTHA</b>s after quenching with three electrophilic reagents (<b>4a</b>–<b>c</b>). The possible mechanism of formation of <b>DTHA</b>s was proposed. In addition, two unsymmetrical <b>DTHA</b>s were confirmed by X-ray single-crystal analyses

Small Molecules of Cyclopentadithiophene Derivatives: Effect of Sulfur Atom Position and Substituted Groups on Their UV–Abs Properties

Thiophene-based organic semiconductors used as the active components have received much attention. Their photoelectric properties can be easily tuned with various substitutions at different positions on molecular structures. Here, we synthesized series cyclopentadithiophene (CDT) derivatives with sulfur atoms at <i>ortho</i>- (<i>o</i>-CDT), <i>meta</i>- (<i>m</i>-CDT), and <i>para</i>-positions (<i>p</i>-CDT) of the bridge carbon. These CDT derivatives were substituted by carbonyl/dicyanomethylene at the bridge position and/or by phenyl groups at the α position, respectively. Due to the different conjugation extent and the variation of donor–acceptor (D–A) interaction originating from the change of sulfur atom position, diverse absorption spectra were observed. Especially for dicyanomethylene substituted <i>o</i>-CDT with phenyl as substitution group (DPCN-<i>o</i>-CDT), its absorption spectrum covers the whole region of visible light. Combining with the electrochemical behaviors and theoretical calculations, it was found that the sulfur atoms mainly contribute to the molecular conjugation in these CDT derivatives, especially for <i>o</i>-CDT derivatives. For phenyl groups, they primarily act as electron donor in <i>m</i>-CDT derivatives, and chiefly contribute to molecular conjugation in <i>p</i>-CDT derivatives, and simultaneously work as electron donor and conjugation component in <i>o</i>-CDT derivatives, respectively