Aryl substituents navigate the course of Scholl-type oxidative coupling in tetraarylthiophenes, enabling selective mono- versus dual cyclizations via electronic step discrimination and control. Guided by Hammett σ _p constants, this study deciphers reactivity trends, face selectivity, excellent control, and coupling pathways—offering a predictive blueprint for regioselective π-architecture construction.

Abstract

Scholl-type oxidative aryl-aryl coupling is a powerful strategy for constructing extended π-systems, yet achieving regioselectivity and stepwise control remains a formidable challenge. Here, we report a systematic study on tetraarylthiophene (TAT) frameworks, revealing how subtle electronic effects of aryl substituents govern C─C bond formation efficiency, selectivity, and pathways. Guided by electrochemical potentials and Hammett σ _p constants, we establish a reactivity trend—OMe > Me > ^t Bu > H > Ph > F > Cl > CHO > CF₃—revealing that electron-rich aryls promote efficient coupling, while electron-deficient groups suppress reactivity. Crucially, face-selective mono-cyclization products (PTs) are achieved by electronic step discrimination, where strategically pairing electronically distinct aryls steers homo- versus cross-coupling outcomes, enabling precise control over sequential couplings. Our findings unveil a simple yet powerful electronic map to predict coupling outcomes, product evolution, and opens a rational path to design regioselective oxidative cyclizations in polyaryl architectures toward precise π-frameworks.