Stepwise Construction of Head-to-Tail-Type Oligothiophenes via Iterative Palladium-Catalyzed CH Arylation and Halogen Exchange

The effect of side-chain branch position on the thermal properties of poly(3-alkylthiophenes)

Branching closer to the backbone causes tighter packing in the side-chain direction and lower side chain and backbone dynamics.

Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: A Review

Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical, and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter, or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article.

Room-Temperature Direct β-Arylation of Thiophenes and Benzo[b]thiophenes and Kinetic Evidence for a Heck-type Pathway

The first example of a regioselective β-arylation of benzo[b]thiophenes and thiophenes at room temperature with aryl iodides as coupling partners is reported. This methodology stands out for its operational simplicity: no prefunctionalization of either starting material is required, the reaction is insensitive to air and moisture, and it proceeds at room temperature. The mild conditions afford wide functional group tolerance, often with complete regioselectivity and high yields, resulting in a highly efficient catalytic system. Initial mechanistic studies, including ¹³C and ²H KIEs, suggest that this process occurs via a concerted carbo-palladation across the thiophene double bond, followed by a base-assisted anti-elimination.

Synthesis of heteroarenes dyads from heteroarenes and heteroarylsulfonyl chlorides via Pd-catalyzed desulfitative C–H bond heteroarylations

We report palladium-catalyzed synthesis of heteroarenes dyads using heteroarylsulfonyl chlorides as coupling partners. The C–H bond functionalizations occurred at α-position with pyrroles and furans, while at β-position with thiophenes.

Oligothiophene semiconductors: synthesis, characterization, and applications for organic devices

Oligothiophenes provide a highly controlled and adaptable platform to explore various synthetic, morphologic, and electronic relationships in organic semiconductor systems. These short-chain systems serve as models for establishing valuable structure-property relationships to their polymer analogs. In contrast to their polymer counterparts, oligothiophenes afford high-purity and well-defined materials that can be easily modified with a variety of functional groups. Recent work by a number of research groups has revealed functionalized oligothiophenes to be the up-and-coming generation of advanced materials for organic electronic devices. In this review, we discuss the synthesis and characterization of linear oligothiophenes with a focus on applications in organic field effect transistors and organic photovoltaics. We will highlight key structural parameters, such as crystal packing, intermolecular interactions, polymorphism, and energy levels, which in turn define the device performance.

Synthesis of 2,5-diaryl-substituted thiophenes as helical mimetics: towards the modulation of islet amyloid polypeptide (IAPP) amyloid fibril formation and cytotoxicity

A range of 2,5-diarylated thiophenes were synthesised as small molecule mimetics of the α-helix to modulate the amyloidogenesis and cytotoxic effect of islet amyloid polypeptide (IAPP). 3-Substituted thiophene-2-carboxylic acids were used as key intermediates and functionalised by palladium decarboxylative cross-coupling and direct C-H activation successively with overall yields ranging from 23 to 95 %. The effect of the ligands on IAPP amyloid fibril formation was evaluated with the thioflavin T (ThT) fluorescence-based assay. Furthermore, the capacity of these compounds to inhibit the cytotoxic effect of IAPP was assessed using β-pancreatic cells.

Facile and selective synthesis of oligothiophene-based sensitizer isomers: an approach toward efficient dye-sensitized solar cells

Two sets of isomeric organic dyes with n-hexyl (DH and AH) or 2-ethylhexyl (DEH and AEH) groups substituted at the spacer part have been designed and straightforwardly synthesized via a facile and selective synthetic route. The structure difference between the isomers stands at the position of the incorporated alkyl chains which are introduced into the terthiophene spacer close to the donor (D) or anchor (A) side. The relationship between the isomeric structures and the optoelectronic properties are systematically investigated. It is found that, in the D series dyes, the alkyl group is much closer to the aromatic donor moiety, which brings about strong steric hindrance and therefore causes a remarkable twist in the molecular skeleton. In contrast, a more planar chemical structure and more effective π-conjugation are realized in the A series dye isomers. Consequently, the A series isomeric dyes demonstrate bathochromically shifted absorption bands, resulting in the improved light-harvesting capability and enhanced photo-generated current. However, the D series isomeric dyes with more twisted molecular skeleton have suppressed the intermolecular interactions and retarded the charge recombination more efficiently, which induces higher open-circuit photovoltage. Combining the two effects on the performance of the fabricated dye-sensitized solar cells (DSSC), the influence from the short-circuit photocurrent plays a more significant role on the power conversion efficiency (η). As a result, isomer AEH-based DSSC with quasi-solid-state electrolyte displays the highest η of 7.10% which remained at 98% of the initial value after continuous light soaking for 1000 h. Promisingly, a η of 8.66% has been achieved for AEH-based DSSC with liquid electrolyte containing Co(II)/(III) redox couple. This work presents the crucial issue of molecular engineering and paves a way to design organic sensitizers for highly efficient and stable DSSCs.

Highly ordered mesoporous TiO2-Fe2O3 mixed oxide synthesized by sol-gel pathway: an efficient and reusable heterogeneous catalyst for dehalogenation reaction

Highly ordered two-dimensional (2D) hexagonal TiO(2)-Fe(2)O(3) mixed-oxide material MFT-1, which is composed of very tiny nanoparticles, is synthesized using sodium dodecylsulfate (SDS) as a structure-directing agent. Interestingly, synthesis of an ordered mesophase was not possible using SDS as a template for mesoporous pure Fe(2)O(3) or TiO(2) phases. This mesoporous iron-titanium mixed-oxide material has been characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), N(2) sorption, ultraviolet-visible light diffuse reflectance spectroscopy (UV-vis DRS) studies. N(2) sorption analysis revealed high surface areas (126-385 m(2) g(-1)) and narrow pore size distributions (3.1-3.4 nm) for different samples. UV-vis DRS spectra and wide-angle powder XRD patterns indicate that the material is composed of α-Fe(2)O(3) and anatase TiO(2) phases. This TiO(2)-Fe(2)O(3) mixed-oxide material can act as a very efficient and reusable catalyst in the dehalogenation of aromatic chloride-, bromide-, and iodide-tolerating -F, -CN, -CH(3), -OCH(3) and -NO(2) functional groups in the aromatic ring using 2-propanol as the dispersion medium.

Silver-mediated palladium-catalyzed direct C-H arylation of 3-bromoisothiazole-4-carbonitrile

Silver(I) fluoride-mediated Pd-catalyzed C-H direct arylation/heteroarylation of 3-bromoisothiazole-4-carbonitrile (1a) gives twenty-four 5-aryl/heteroaryl-3-bromoisothiazole-4-carbonitriles. The reaction was partially optimized with respect to catalyst, ligand, and base. During this study 3,3'-dibromo-5,5'-biisothiazole-4,4'-dicarbonitrile (3a) was isolated as a byproduct and subsequently prepared via the silver-mediated Pd-catalyzed oxidative dimerization of 3-bromoisothiazole-4-carbonitrile in 67% yield. The analogous phenylation and oxidative dimerization of 3-chloroisothiazole-4-carbonitrile (1b) gave 3-chloro-5-phenylisothiazole-4-carbonitrile (4) and 3,3'-dichloro-5,5'-biisothiazole-4,4'-dicarbonitrile (3b) in 96% and 69% yields, respectively.