Consecutive Thiophene-Annulation Approach to π‑Extended Thienoacene-Based Organic Semiconductors with [1]Benzothieno[3,2‑b][1]benzothiophene (BTBT) Substructure

We describe a new synthetic route to the [1]­benzothieno­[3,2-b]­[1]­benzothiophene (BTBT) substructure featuring two consecutive thiophene-annulation reactions from o-ethynyl-thioanisole substrates and arylsulfenyl chloride reagents that can be easily derived from arylthiols. The method is particularly suitable for the synthesis of unsymmetrical derivatives, e.g., [1]­benzothieno­[3,2-b]­naphtho­[2,3-b]­thiophene, [1]­benzothieno­[3,2-b]­anthra­[2,3-b]­thiophene, and naphtho­[3,2-b]­thieno­[3,2-b]­anthra­[2,3-b]­thiophene, a selenium-containing derivative, [1]­benzothieno­[3,2-b]­[1]­benzoselenophene. It also allows us to access largely π-extended derivatives with two BTBT substructures, e.g., bis[1]­benzothieno­[2,3-d:2′,3′-d′]­benzo­[1,2-b:4,5-b′]­dithiophene and bis[1]­benzothieno­[2,3-d:2′,3′-d′]­naphtho­[2,3-b:6,7-b′]­dithiophene (BBTNDT). It should be emphasized that these new BTBT derivatives are otherwise difficult to be synthesized. In addition, since various substrates and reagents, o-ethynyl-thioanisoles and arylthiols, respectively, can be combined, the method can be regarded as a versatile tool for the development of thienoacene-based organic semiconductors in this class. Among the newly synthesized materials, highly π-extended BBTNDT afforded very high mobility (>5 cm2 V–1 s–1) in its vapor-deposited organic field-effect transistors (OFETs), which is among the highest for unsubstituted acene- or thienoacenes-based organic semiconductors. In fact, the structural analyses of BBTNDT both in the single crystal and thin-film state indicated that an interactive two-dimensional molecular array is realized in the solid state, which rationalize the higher carrier mobility in the BBTNDT-based OFETs.