Cyclic oligoarylenes have long received considerable attention due to their structural, electronic, and optical properties. The most representative arylenes are phenylenes, in which the phenyl groups can be connected to each other in three ways, i.e., at the o-, m-, or p-positions. Of these, cyclo-o-phenylenes are of little interest and are not very well explored. Even so, biphenylene, triphenylene, tetraphenylene, hexaphenylene, and octaphenylene derivatives have already been synthesized (Fig. ), and their reactivity, structural properties, and applications have been investigated. Replacing the benzene rings with thiophene rings allows modifying the electronic and structural properties to induce, for example, weaker aromaticity, lower steric hindrance, and intermolecular S•••S interactions in the solid state. Structurally, cyclo-o-phenylenes correspond approximately to cyclic oligo(3,4-thienylene)s in as much that the thiophene rings are linked at the β,βʹ-positions (Fig. ). To date, cyclic oligo(3,4-thienylene)s with two to four thiophene rings 4 have been explored. Given that all their αpositions are reactive sites, tri-and tetra(3,4-thienylene)s (3T and 4T) can be transformed into a variety of electron-rich πconjugated molecules, such as heterosumanenes and hetero [8]circulenes, 6 as well as tetra(3,4-thienylene)s can be employed as e.g., 3D building blocks 7 or solvent-responsive molecular assemblies. In addition, tri(3,4-thienylene)s have been studied as charge-transfer complexes or planar [6]radialenes. However, cyclic oligo(3,4-thienylene)s with five or more thiophene rings have not yet been synthesized. To create larger β,βʹ-linked cyclic oligo(3,4-thienylene)s, building blocks that contain functional groups at the β-positions are a prerequisite. In 2017, a practical synthetic method for a βsubstituted unit, i.e., a 3,4-diborylated thiophene derivative, was developed by Osuka, Tanaka, and co-workers, which widened the range of synthetic approaches for cyclic macrocycles that contain 3,4-thienylenes and other heteroarenes. Herein, we report the synthesis of penta-and hexa(3,4thienylene)s (5T and 6T) via Pd-catalyzed cross-coupling and Nimediated homocoupling reactions using 3,4-diborylthiophene 1 or the newly synthesized 4,4ʹ-diboryl-3,3ʹ-bithiophene 2 (Figs. and). The structures and electronic properties of 5T and 6T were determined using NMR and X-ray crystallography as well as UV-vis absorption spectroscopy. The structural characteristics and optoelectronic properties of 5T and 6T were compared to those of 4T and examined using density functional theory (DFT) calculations.