Palladium-PEPPSI-NHC Complexes Bearing Imidazolidin-2-Ylidene Ligand: Efficient Precatalysts for the Direct C5-Arylation of N-Methylpyrrole-2-Carboxaldehyde


KALOĞLU M. , Kaloglu N., ÖZDEMİR İ.

CATALYSIS LETTERS, 2021 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume:
  • Publication Date: 2021
  • Doi Number: 10.1007/s10562-021-03561-4
  • Title of Journal : CATALYSIS LETTERS

Abstract

The Pd-catalyzed direct arylation of pyrroles is an important research field for organic synthesis and catalysis chemistry. However, imidazolidin-2-ylidene based Pd-NHC complexes (NHC=N-heterocyclic carbene) have not yet been employed as catalysts for the direct C5 mono-arylation of C2-substituted N-methylpyrrole derivatives with aryl halides. Therefore, we now report the synthesis and characterization of new 1,3-bis(substituted benzyl) imidazolinium salts as carbene precursors, and their corresponding Pd-PEPPSI-NHC type complexes (PEPPSI=Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation). The catalytic properties of these complexes have been evaluated in the direct C5 mono-arylation of N-methylpyrrole-2-carboxaldehyde with a wide variety of (hetero)aryl halides. This environmentally attractive procedure has also been found to be tolerant to a wide variety of functional groups on the aryl halides such as formyl, acetyl, nitrile, fluoro or trifluoromethyl, and good yields have been obtained in presence of 1 mol% catalyst loading at 120 degrees C.