title: Synthesis of Benzothiadiazole Derivatives by Applying C-C Cross-Couplings.
abstract: The benzothiadiazole moiety has been extensively exploited as a building block in the syntheses of efficient organic semiconducting materials during the past decade. In this paper, parallel synthetic routes to benzothiadiazole derivatives, inspired by previous computational findings, are reported. The results presented here show that various C-C cross-couplings of benzothiadiazole, thiophene, and thiazole derivatives can be efficiently performed by applying Xantphos as a ligand of the catalyst system. Moreover, improved and convenient methods to synthesize important chemical building blocks, e.g., 4,7-dibromo-2,1,3-benzothiadiazole, in good to quantitative yields are presented. Additionally, the feasibility of Suzuki-Miyaura and direct coupling methods are compared in the synthesis of target benzothiadiazole derivatives. The computational characterization of the prepared benzothiadiazole derivatives shows that these compounds have planar molecular backbones and the possibility of intramolecular charge transfer upon excitation. The experimental electrochemical and spectroscopic studies reveal that although the compounds have similar electronic and optical properties in solution, they behave differently in solid state due to the different alkyl side-group substitutions in the molecular backbone. These benzothiadiazole derivatives can be potentially used as building blocks in the construction of more advanced small molecule organic semiconductors with acceptor-donor-acceptor motifs.
authors.affiliation: Research Unit of Sustainable Chemistry, University of Oulu , P.O. Box 3000, FI-90014 Oulu, Finland.
authors.forename: Juha P
authors.initials: JP
authors.lastname: Heiskanen
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology , P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Paola
authors.initials: P
authors.lastname: Vivo
authors.affiliation: Research Unit of Sustainable Chemistry, University of Oulu , P.O. Box 3000, FI-90014 Oulu, Finland.
authors.forename: Niko M
authors.initials: NM
authors.lastname: Saari
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology , P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Terttu I
authors.initials: TI
authors.lastname: Hukka
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology , P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Tuuva
authors.initials: T
authors.lastname: Kastinen
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology , P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Kimmo
authors.initials: K
authors.lastname: Kaunisto
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology , P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Helge J
authors.initials: HJ
authors.lastname: Lemmetyinen
authors.affiliation: Research Unit of Sustainable Chemistry, University of Oulu , P.O. Box 3000, FI-90014 Oulu, Finland.
authors.forename: Osmo E O
authors.initials: OE
authors.lastname: Hormi