In this work, an attempt to planarize 2,3,4,6- tetraarylthieno[3,2-b]thiophene based on the FeCl3 oxidative annulation was described. Thus, two cyclized 2,3,5,6-tetraarylthieno[3,2-b]thiophenes 5a and 5b were synthesized in moderate yields. NMR and HR-MS analysis indicated the annulation between only one pair of the phenyl substituents. | JOURNAL OF SCIENCE OF HNUE DOI Natural Sci. 2016 Vol. 61 No. 9 pp. 34-41 This paper is available online at http AN ATTEMPT TO PLANARIZE 2 3 5 6-TETRAARYLTHIENO 3 2-b THIOPHENE BY FeCl3-ASSISTED ANNULATION Nguyen Hien1 and Nguyen Thi Lieu2 1 Faculty of Chemistry Hanoi National University of Education 2 Faculty of Chemistry Hanoi Metropolitan University Abstract. Thieno 3 2-b thiophene is a typical core structure in a number of conjugated organic opto-electronic materials. In this work an attempt to planarize 2 3 4 6- tetraarylthieno 3 2-b thiophene based on the FeCl3 oxidative annulation was described. Thus two cyclized 2 3 5 6-tetraarylthieno 3 2-b thiophenes 5a and 5b were synthesized in moderate yields. NMR and HR-MS analysis indicated the annulation between only one pair of the phenyl substituents. Keywords Thieno 3 2-b thiophene Suzuki-Miyaura reaction FeCl3 oxidative annulation. 1. Introduction Thieno 3 2-b thiophene TT has been used as a key monomer or incorporated in functionalized oligomers and polymers developed as p-type organic semi-conductors optoelectronics and electroluminescence 1 . The inter-molecular sulfur-sulfur interactions allow materials containing this core structure to increase the electronic transport between adjacent molecules. Skabara and co-workers reported on the synthesis of two novel TT-based conjugated molecules A and B starting from Stille coupling reactions of dibromo_TTand stannylthiophenes Figure 1 2 . Electro-chemical and optical investigations provided the repeating band gaps as and eV for A and and eV for B. While non-covalent S O interactions in A resulted in a planar conformation and hence a high degree of conjugation length the twisted conformation was observed for the 3 4-ethylenedithiothiophene analogue B. As expected the hole mobilities for A and B were reported to be and 10 2cm2V 1s 1 respectively. A similar phenomenon was observed by Frere who .
