Reactivity of 3-(pyrrol-1-yl)thiophenes in Pd-catalysed direct arylations

Imen Smari (1, 2) , Chiraz Youssef (2) , Hamed Ben Ammar (2) , Bechir Ben Hassine (2) , Jean-François Soulé (1) , Henri Doucet (1)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 Laboratoire de Synthèse Organique Asymétrique et Catalyse Homogène

The regioselectivity of the Pd-catalysed direct arylation of 3-(pyrrol-1-yl)thiophene derivatives was investigated. Conditions allowing either the regioselective arylation at C2 or at C5 of the thiophene ring are reported. From methyl 3-(pyrrol-1-yl)thiophene-2-carboxylate using KOAc as the base, DMA as the solvent and only 1 mol % Pd(OAc)2 catalyst, the target 5-arylated thiophenes were obtained in moderate to good yields with a wide variety of aryl halides; whereas the use of 1-(4-methylthiophen-3-yl)-pyrrole affords the C2-arylated thiophenes. The sequential palladium catalysed 2,5-diheteroarylation of such 3-(pyrrol-1-yl)thiophene is also reported allowing the access to thiophenes bearing two different aryl units at C2 and C5. A pyrazole bearing an ester substituent at C4 and a pyrrole substituent at C5 was only arylated at C2 on the pyrrole ring.

Mots clés: Palladium; Catalysis; C–H bond activation; Thiophenes pyrroles; Direct arylation; Aryl halides

Domaines: Catalyse

Imen Smari, Chiraz Youssef, Hamed Ben Ammar, Bechir Ben Hassine, Jean-François Soulé, et al.. Reactivity of 3-(pyrrol-1-yl)thiophenes in Pd-catalysed direct arylations. Tetrahedron, 2015, 71 (37), pp.6586-6593. ⟨10.1016/j.tet.2015.03.022⟩. ⟨hal-01149179⟩