D-π-D chromophores based on dithieno[3,2-b:2',3'-d]thiophene (DTT): Potential application in the fabrication of solar cell

Efficient access to materials-oriented aromatic alkynes via the mechanochemical Sonogashira coupling of solid aryl halides with large polycyclic conjugated systems

Sonogashira coupling represents an indispensable tool for the preparation of organic materials that contain C(sp)-C(sp2) bonds. Improving the efficiency and generality of this methodology has long been an important research subject in materials science. Here, we show that a high-temperature ball-milling technique enables the highly efficient palladium-catalyzed Sonogashira coupling of solid aryl halides that bear large polyaromatic structures including sparingly soluble substrates and unactivated aryl chlorides. In fact, this new protocol provides various materials-oriented polyaromatic alkynes in excellent yield within short reaction times in the absence of bulk reaction solvents. Notably, we synthesized a new luminescent material via the mechanochemical Sonogashira coupling of poorly soluble Vat Red 1 in a much higher yield compared to those obtained using solution-based conditions. The utility of this method was further demonstrated by the rapid synthesis of a fluorescent metal-organic framework (MOF) precursor via two sequential mechanochemical Sonogashira cross-coupling reactions. The present study illustrates the great potential of Sonogashira coupling using ball milling for the preparation of materials-oriented alkynes and for the discovery of novel functional materials.

An Effective Route to Dithieno[3,2-b:2′,3′-d]thiophene-Based Hexaheteroacenes

A series of 12H-[1]benzo[4′′,5′′]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]indoles were efficiently prepared in three steps starting from available benzo[b]thieno[2,3-d]thiophen-3(2H)-ones. These fused ketones were treated with the Vilsmeier reagent and hydroxylamine hydrochloride to give the corresponding 3-chlorobenzo[b]thieno[2,3-d]thiophene-2-carbonitriles, which then reacted with methyl sulfanylacetate to form methyl 3-aminobenzo[4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]thiophene-2-carboxylates, in accordance with the Fiesselmann thiophene synthesis protocol. Finally, the desired N,S-heterohexacenes were obtained by conversion of these fused 3-aminothiophene-2-carboxylates into the corresponding 3-aminothiophene intermediates, which acted as synthetic equivalents of thiophen-3(2H)-ones, followed by their acid-promoted reaction with arylhydrazines, in accordance with the Fischer indolization procedure.