The bis-NHC–Ag/Pd(OAc)2 catalytic system (NHC = N-heterocyclic carbene), a combination of bis-NHC–Ag complex and Pd(OAc)2, was found to be a smart catalyst in the Pd-catalyzed transfer hydrogenation of various functionalized arenes and internal/terminal alkynes. The catalytic system demonstrated high efficiency for the reduction of a wide range of various functional groups such as carbonyls, alkynes, olefins, and nitro groups in good to excellent yields and high chemoselectivity for the reduction of functional groups. In addition, the protocol was successfully exploited to stereoselectivity for the transformation of alkynes to alkenes in aqueous media under air. This methodology successfully provided an alternative useful protocol for reducing various functional groups and a simple operational protocol for transfer hydrogenation.
Palladium-catalyzed room temperature transfer hydrogenation of azo compounds using recyclable polymer-supported formate as the hydrogen donor produces corresponding amine(s) in excellent yields (88%98%). This method was found to be highly facile with selectivity over a number of other functional groups such as halogen, alkene, nitrile, carbonyl, amide, methoxy, and hydroxyl.Key words: azo compounds, catalytic transfer hydrogenation, polymer-supported formate, 10% Pd-C, amines.
A new (NNN) tridentate ligand was prepared, and its ability to coordinate ruthenium(II) was evaluated. The presence of different functional groups on the ligand allows bi- or tri-coordinated complexes to be obtained depending on complexation conditions. The catalytic activity of both bidentate and tridentate complexes was studied in asymmetric transfer hydrogenation of different aryl ketones, showing a comparable behavior of the two complexes in terms of efficiency and stereoselectivity.
AbstractEfficient chemoselective transfer hydrogenation of the C=C bond of α,β-unsaturated ketones has been developed, using the iridium complexes containing pyridine-imidazolidinyl ligands as catalysts and formic acid as a hydrogen source. In comparison with organic solvents or H2O as solvent, the mixed solvents of H2O and MeOH are critical for a high catalytic chemoselective transformation. This chemoselective transfer hydrogenation can be carried out in air, which is operationally simple, allowing a wide variety of α,β-unsaturated substrates with different functional groups (electron-donating and electron-withdrawing substituents) leading to chemoselective transfer hydrogenation in excellent yields. The practical application of this protocol is demonstrated by a gram-scale transformation.
Bis-NHC–Ag/Pd(OAc)2 Catalytic System Catalyzed Transfer Hydrogenation Reaction
