Pentaleno[1,2-c:4,5-c′]dithiophene Derivatives: First Synthesis, Properties, and a Molecular Structure

Abstract

New π-extended pentalene derivatives bearing two thiophene rings are synthesized from 3-bromo-4-ethynylthiopenes as stable orange crystals by using a nickel complex. The observed electronic properties and molecular structure clearly indicate low contribution of the pentalene π system as predicted by the TD-DFT calculations.

Gold‐Catalyzed Cyclization of Diynes: Controlling the Mode of 5‐endo versus 6‐endo Cyclization—An Experimental and Theoretical Study by Utilizing Diethynylthiophenes

“…The unsymmetrical substituted 5,5,5-thiopheno [c]pentalene ring is a very interesting motif, and to date no compounds derived from this motif are known. [14] Especially in the context of material science, there has been a broad interest in pentalene-motif-containing compounds, such as dibenzopentalenes, [15] whereas the heteroaromatic analogues have been much less explored presumably caused by their difficult synthetic access. Initial attempts to cyclize the diyne systems followed by a NÀ H or OÀH insertion employing compounds, such as 1 f or 1 g failed (Table 1, entry 6,7).…”

The B(C6F5)3 Boron Lewis Acid Route to Arene‐Annulated Pentalenes

“…Kawase and coworkers have already reported that dibenzopentalene derivatives exhibit characteristic absorption spectra with a very weak absorption band in the long‐wavelength region around 600 nm 3b. 4, 17 They also demonstrated that this absorption band is attributable to forbidden HOMO–LUMO transitions, which are one of the characteristics of 4nπ electron systems. We have recently reported the electronic effect of electron‐withdrawing C 6 F 5 groups on the electronic structure of dibenzopentalenes, leading to significant bathochromic shifts of the absorption bands 7.…”

“…Work‐up eventually gave the product 23 as a red‐brown solid, isolated in 40 % yield. The X‐ray crystal structure analysis (single crystals were obtained from CH 2 Cl 2 /pentane at room temperature by the diffusion method) revealed that the HB(C 6 F 5 ) 2 addition product to a thieno‐annulated benzopentalene system17, 18 had been obtained. Product 23 features a C 6 F 5 group and a phenyl substituent at the central pentalene‐derived unit.…”

Dithieno[a,e]pentalene Based Conjugated Polymers: Synthesis and Characterization

“…[25][26][27] Some pentalene derivatives such as dibenzopentalenes have been perceived as useful building blocks for synthesis of conjugated polymers because of their rigid planar and conjugated structure. [28][29][30][31][32] Small molecules based on dibenzopentalenes have been synthesized and applied in organic electronic devices. [31] Substituted dithieno[a,e]pentalenes (DTPs) are stable compounds and the efficient synthetic methods for them have been developed lately.…”

“…[31] Substituted dithieno[a,e]pentalenes (DTPs) are stable compounds and the efficient synthetic methods for them have been developed lately. [28,29] The DTPs can be interesting building blocks for conjugated polymers. However, the application of DTP derivatives as building blocks for conjugated polymer has never been reported.…”