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A Mixed N‐Heterocyclic Carbene/2,2′‐Bipyridine‐Supported Robust Ruthenium(II) Oxidation Precatalyst for Benzylic C−H Oxidation
Author(s) -
Gupta Suraj K.,
Choudhury Joyanta
Publication year - 2017
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201700177
Subject(s) - ruthenium , carbene , chemistry , catalysis , denticity , ligand (biochemistry) , oxidizing agent , bipyridine , medicinal chemistry , redox , combinatorial chemistry , polymer chemistry , organic chemistry , metal , crystal structure , biochemistry , receptor
Catalytic oxidation of hydrocarbons to the oxygenated derivatives has been an important research area for a long time and the search for well‐defined, tunable, efficient, selective, and robust oxidation (pre)catalysts is still on. To further develop the applicability of N‐heterocyclic carbene (NHC) ligands, herein we report a mixed NHC/bipyridine‐supported ruthenium(II) oxidation precatalyst, [(N py ^C NHC )Ru II (N py ^N py )(CH 3 CN) 2 ](PF 6 )(CF 3 SO 3 ), 1 (N py ^C NHC =a bidentate ′2‐pyridyl‐NHC′ neutral ligand, N py ^N py =2,2′‐bipyridine) consisting of two cis ‐disposed loosely bound solvent ligands, which was successfully utilized for catalytic benzylic C−H oxidation of a variety of aromatic hydrocarbons to the corresponding ketones in 65–90 % yields with the mild sacrificial oxidant NaIO 4 . The ligand backbone was found to be robust under oxidizing conditions. The presence of these ligands around the ruthenium center was crucial for the system, as the known RuCl 3 /NaIO 4 and [Ru( para ‐cymene)Cl 2 ] 2 /NaIO 4 combinations were proved to be completely ineffective precatalysts under similar conditions. The scope and mechanistic aspects of this precatalyst were also evaluated.