C[sbnd]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 1-cinnamyl- N -alkylbenzimidazolium salts, namely trans -dichloro[1,3-dicinnamyl-benzimidazol-2-yliden]pyridine palladium(II) (3a), trans -dichloro[1-cinnamyl-3-benzyl-benzimidazol-2-yliden]pyridine palladium(II) (3b), trans -dichloro[1-cinnamyl-(fluorobenzyl)-benzimidazol-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), as precatalyst for the cross-coupling reactions between furanyl and thiofuranyl derivatives and arylbromides via C–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. [Display omitted] 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), trans -dichloro[1-cinnamyl-3-benzyl-benzimidazol-2-yliden]pyridine palladium(II) (3b), trans -dichloro[1-cinnamyl-(fluorobenzyl)-benzimidazol - 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), as precatalyst for the cross-coupling reactions between furanyl and thiofuranyl derivatives and arylbromides via C 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. [ABSTRACT FROM AUTHOR]