C-H - H activation of furanyl and thiofuranyl substrates catalyzed by trans-dichloro[1-cinnamyl-3-arylmethyl-benzimidazol-2-yliden]pyridine palladium(II) complexes

The present study explores the potential of six NHC-palladium(II) complexes derived from N-cinnamyl- N '- alkylbenzimidazolium salts, namely trans-dichloro[1,3-dicinnamyl-benzimidazol-2-yliden]pyridine palladium(II) (3a), 3a ), trans-dichloro[1-cinnamyl-3-benzyl-benzimidazol-2-yliden]pyridine palladium(II) (3b), 3b ), trans-dichloro[1- cinnamyl-(fluorobenzyl)-benzimidazol-2-yliden]pyridine- 2-yliden]pyridine palladium(II) (2-fluorobenzyl 3c , 3-fluorobenzyl 3d and 4-fluorobenzyl 3e ,) and trans-dichloro[1-cinnamyl-(4-nitrobenzyl)-benzimidazol-2-yliden]pyridine palladium(II) (3f), 3f ), as precatalyst for the cross-coupling reactions between furanyl and thiofuranyl derivatives and arylbromides via C-H - H activation of the heterocycles. The structure of the six palladium(II) complexes has been elucidated through the use of multinuclear NMR, FT-IR and mass spectroscopy. Furthermore, the square-planar geometry of the organometallic ion was confirmed by single crystal X-ray diffraction study carried out on complex 3c . The latter complex proved to be the most effective precatalyst agent, with observed conversions higher than 78% when 4-bromoacetophenone and 1-bromonaphthalene were employed.