An efficient domino protocol towards high-performance organic semiconductors: [1]benzothiophene[3,2-b][1]benzothiophenes

Abstract

A highly efficient synthetic method toward [1]benzothiophene[3,2-b][1]benzothiophenes (BTBTs), which are high-performance organic semiconductors, through a domino reaction has been developed. This protocol features inexpensive and readily available starting materials, catalyst-free reaction, simple operation under air atmosphere, good yields, and wide substrate applicability. Notably, this method represents one of the most efficient methods for synthesizing BTBTs, constructing four C–S bonds and one CC bond through a domino reaction. Based on mechanistic study, two plausible reaction pathways were proposed: a hydrosulfuric anion nucleophilic mechanism and a sulfur free radical mechanism. The great potential applications of this reaction were demonstrated through gram-scale synthesis, transformations, and respectable photophysical properties. More importantly, organic field-effect transistors (OFETs) prepared by spin-coating showed an average mobility of 1.143 cm² V⁻¹ s⁻¹ for C₈-BTBT and 0.032 cm² V⁻¹ s⁻¹ for 3^tBu-BTBT. Thus, this study has laid the foundation for the development of new BTBT materials such as 3C_n-BTBT.