title: Hindered aryl bromides for regioselective palladium-catalysed direct arylation at less favourable C5-carbon of 3-substituted thiophenes.
abstract: The use of the congested aryl bromide 2-bromo-1,3-dichlorobenzene as coupling partner allows to modify the regioselectivity of the arylation of 3-substituted thiophene derivatives in favour of carbon C5. The coupling of this aryl bromide with a variety of 3-substituted thiophenes gave in all cases the desired 5-arylation products in moderate to good yields using only 0.5 mol % of a phosphine-free and air-stable palladium catalyst. Then, from these 5-arylthiophenes, a second palladium-catalysed C-H bond functionalization at C2 of the thiophene ring allows the synthesis of 2,5-diarylthiophenes with two different aryl units.
authors.affiliation: Institut Sciences Chimiques de Rennes, UMR 6226 CNRS-Université de Rennes "Organometalliques, Material and Catalysis", Campus de Beaulieu, 35042 Rennes, France. ; Tel: +33 (0)2-23-23-63-84.
authors.forename: Rongwei
authors.initials: R
authors.lastname: Jin
authors.affiliation: Institut Sciences Chimiques de Rennes, UMR 6226 CNRS-Université de Rennes "Organometalliques, Material and Catalysis", Campus de Beaulieu, 35042 Rennes, France. ; Tel: +33 (0)2-23-23-63-84.
authors.forename: Charles Beromeo
authors.initials: CB
authors.lastname: Bheeter
authors.affiliation: Institut Sciences Chimiques de Rennes, UMR 6226 CNRS-Université de Rennes "Organometalliques, Material and Catalysis", Campus de Beaulieu, 35042 Rennes, France. ; Tel: +33 (0)2-23-23-63-84.
authors.forename: Henri
authors.initials: H
authors.lastname: Doucet
keywords: C–H bond activation; aryl bromides; atom economy; palladium; regioselectivity; thiophenes