Selective α And β-Arylation Of Furan Ring Of(ortho-Bromo-phenyl)- Furan-2-yl-methanones And Synthesis Of Polysubstituted Benzothiophenes

The furan derivatives are used extensive in medicinal chemistry, synthetic plastics, chemical pesticides. The transformation of furan has been attracted a high interest from organic chemists.Transition-metal-catalyzed carbon-carbon cleavage offers significant opportunities to develop novel transformations. But the rection conditions are usually harsh since the thermodynamic stability of the C-C bond. So the development of new methodologies in the chemistry of C-C bond cleavage is in urgent need. The area of transition-metal-catalyzed direct arylation through cleavage of C-H bonds has undergone rapid development in recent years, and is becoming an increasingly viable alternative to traditional crossing-coupling reactions with organometallic reagents. Therefore, it represents an environmentally and economically more attractive strategy.The first part of work: We described an unexpected palladium-catalyzed C(CO)-C bond cleavage of(orth-bromo-phenyl)-furan-2-yl-methanones involving furan ring as a leaving group. This is a new methodology of C-C bond cleavage. And we also avoid of this C(CO)-C bond cleavage to achieve an intramolecular β-arylation of furan ring for the efficient synthesis of unprecented furan-derived fluorenones. Fluorenones are a class of compounds with important biological activities and useful synthetic intermediates.The second part of work: We developed an efficient palladium-catalyzed cross-coupling of readily available furfural tosylhydrazones with 2-iodothiophenol as a novel synthetic route to polysubstituted benzothiophenes. The reaction proceeds via 2-furylmethylene palladium halide intermediates, which undergo concomitant furan ring opening and ring closure to form benzothiophenes; this reaction expands the applications of sustainable furan derivatives as synthetic building blocks.