Synthesis of [PdBr2(benzimidazole-2-ylidene)(pyridine)] complexes and their catalytic activity in the direct C-H bond activation of 2-substituted heterocycles

Lasmari S., Gürbüz N., Boulcina R., Özdemir N., Özdemir İ.

POLYHEDRON, cilt.199, 2021 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 199
  • Basım Tarihi: 2021
  • Doi Numarası: 10.1016/j.poly.2021.115091
  • Dergi Adı: POLYHEDRON
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Chemical Abstracts Core
  • Anahtar Kelimeler: N-Heterocyclic carbene, Benzimidazole, Palladium, C-H bond activation, Arylation, CROSS-COUPLING REACTIONS, LIGAND-FREE PALLADIUM, DIRECT ARYLATION, PEPPSI COMPLEXES, ARYL BROMIDES, PD-PEPPSI, CARBENE COMPLEXES, HECK REACTIONS, NHC, DERIVATIVES
  • İnönü Üniversitesi Adresli: Evet

Özet

A series of unsymmetrical 1,3-disubstituted benzimidazolium chlorides, 2a-f, having two nitrogen atoms substituted by various alkyl groups were synthesized as N-heterocyclic carbene (NHC) precursors in high yields. The benzimidazolium salts are readily converted into the corresponding PEPPSI-type palladium & ndash; NHC complexes 3a-f (PEPPSI = pyridine-enhanced precatalyst preparation, stabilization and initiation). The structures of all the compounds have been characterized by H-1 NMR, C-13 NMR and IR spectroscopy, as well as the X-ray diffraction technique (3a, 3d and 3e), which support the proposed structures. Next, the palladium-NHC-PEPPSI complexes were used as catalysts in the direct C(5)-arylation of 2-acetyl furan and 2-acetylthiophene with various aryl bromides. These complexes exhibited moderate to high catalytic activities and gave C-H activation selectively at the C(5)-position of 2-acetylfuran and 2-acetylthiophene. (C) 2021 Elsevier Ltd. All rights reserved.