β-Selective C-H arylation of thiophenes enabled by α-diimine palladium catalysts

• Published in: Tetrahedron Vol. 186; p. 134872
• Main Authors: Zeng, Qing-Zhao, Wang, Ke, Liu, Feng-Shou
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2025
• ISSN: 0040-4020
• DOI: 10.1016/j.tet.2025.134872

In this study, a series of sterically and electronically tunable acenaphthene-based α-diimine palladium complexes were synthesized and characterized. These complexes were evaluated as catalysts for the β-C-H arylation of thiophene derivatives with arylboronic acids under aerobic conditions. Among them, complex C3, featuring a 3,5-dimethyl-substituted N-aryl moiety, exhibited the highest catalytic activity. Under optimized conditions, C3 enabled the β-selective arylation of a broad scope of thiophene substrates bearing electron-donating and electron-withdrawing substituents, affording the desired products in good to excellent yields. The reaction proceeded efficiently with low catalyst loading and demonstrated high functional group tolerance. This study presents a practical and general catalytic strategy for site-selective C–H functionalization of heteroarenes under mild, air-stable conditions. [Display omitted] •Tunable α-diimine ligands control the steric and electronic properties of Pd catalysts.•Efficient C-H arylation achieved with 2 mol% catalyst under base-free conditions.•Broad scope with thiophenes and arylboronic acids; exclusive β-selectivity observed.•Bench-stable Pd precatalysts and simple setup enable practical and scalable reactions.