Programmed Synthesis of Tetraarylthieno[3,2-b]thiophene by Site-Selective Suzuki Cross-Coupling Reactions of Tetrabromothieno[3,2-b]thiophene

Abstract

Thieno[3,thiophene is a structural motif that can be found in many important organic materials. A number of mono-, diand tetraarylthieno [3,2-b]thiophenes are reported herein. [1]benzothiophene (C 13 BTBT) were shown to demonstrate a very high thin film mobility of 3.1 cm 2 /Vs and 17.2 cm 2 /Vs, respectively, in VD-OFETs. 4b,c Due to intermolecular sulfur-sulfur interactions, materials containing thieno[3,2-b]thiophene may increase the electronic transport between neighboring molecules. The introduction of substituents into the core structure of materials may change electronic properties, solubility as well as molecular packing. 2m For tuning electronic properties, heterocycles have been widely functionalized by many methods, especially, by palladium(0)-catalyzed cross-coupling reactions. 5 It was previously shown that polyhalogenated heterocycles can be regioselectively functionalized by palladium-catalyzed crosscoupling reactions at the carbon-halogen bonds adjacent to the heteroatom. 5 These were controlled by both electronic and steric factors. We recently reported the methodologies for functionalization of N-methyltetrabromopyrrole, 6 tetrabromothiophene, 6 tetrabromoselenophene 7 and tetrabromofuran, 8 based on site-selective palladium(0)-catalyzed Suzuki reactions. Due to the importance of thieno[3,2-b]thiophene in materials science, we were interested in developing a sequential process for the functionalization of thieno [3,2-b]thiophene via site-selective palladium(0)-catalyzed Suzuki reactions of tetrabromothieno[3,2-b]thiophene with boronic acids. We report herein an efficient synthesis of mono-, di-and tetraarylthieno[3,2-b]thiophene using this strategy.The Suzuki-Miyaura reactions of 1 9 (1.0 equiv) with a series of boronic acids (1.2 equiv) resulted in a site-selective formation of 2-aryl-3,5,6-tribromothieno[3,2-b]thiophenes 2a-j 5 in 25-80% yields (Scheme 1 and Table 1). The conditions used were optimized with regard to temperature, solvent, base additive, and water additive. Pd(PPh 3 ) 4 was found to be an efficient catalyst for the current reaction. Other well-known catalyst systems, such as Pd(OAc) 2 /X-Phos, resulted in lower yields of the desired products. All reactions were carried out at 90-110 °C in 4-6 hours. Table 1).

Thienothiophenes, Dithienothiophenes, and Thienoacenes: Syntheses, Oligomers, Polymers, and Properties

“…Derivatives of 46 were prepared in the same manner by either replacing the phenyl substituents with various groups or fusing 1,2-dithiol-3-thione to the benzene or cyclohexene rings (Scheme ) . Tetra-aryl-substituted TTs were also synthesized by using the double Suzuki–Miyaura coupling reaction thermally …”

Site-Selective Cross-Coupling of Polyhalogenated Arenes and Heteroarenes with Identical Halogen Groups

“…For 68, Dang and coworkers reported a C2-selective Suzuki−Miyaura coupling with either one or two equivalents of various arylboronic acids to afford the mono-or bisarylated products (69 and 70). 100 3.3.2. 1,3-Azoles: Thiazole, Imidazole, and Oxazole.…”

“…Finally, similar C2/C5-favored selectivity outcomes have also been reported for thiophene derivatives, such as 2,3,5,6-tetrabromothieno­[3,2- b ]­thiophene ( 68 , Scheme ). For 68 , Dang and coworkers reported a C2-selective Suzuki–Miyaura coupling with either one or two equivalents of various arylboronic acids to afford the mono- or bisarylated products ( 69 and 70 ) …”

Synthesis of some mono and dialkynyl derivatives containing thieno[3,2-b]thiophene ring via Sonogashira alkynylation reaction

“…Monoaryl thiophene derivatives 9 were synthesized via Suzuki reaction [8]. As reported in our group [9] whenever increasing the amount of alkynes gave H-insertion products.…”