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., ÖZDEMİR İ.

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

  • Publication Type: Article / Article
  • Volume: 199
  • Publication Date: 2021
  • Doi Number: 10.1016/j.poly.2021.115091
  • Journal Name: POLYHEDRON
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Chemical Abstracts Core, Index Chemicus (IC)
  • Keywords: 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
  • Ondokuz Mayıs University Affiliated: Yes

Abstract

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-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.