Synergistic H₄NI–AcOH Catalyzed Oxidation of the C_sp³–H Bonds of Benzylpyridines with Molecular Oxygen

The oxidation of benzylpyridines forming benzoylpyridines was achieved based on a synergistic H₄NI–AcOH catalyst and molecular oxygen in high yield under solvent-free conditions. This is the first nonmetallic catalytic system for this oxidation transformation using molecular oxygen as the oxidant. The catalytic system has a wide scope of substrates and excellent chemoselectivity, and this procedure can also be scaled up. The study of a preliminary reaction mechanism demonstrated that the oxidation of the C_sp³–H bonds of benzylpyridines was promoted by the pyridinium salts formed by AcOH and benzylpyridines. The synergistic effect of H₄NI–AcOH was also demonstrated by control experiments

An Effective Method for the Construction of Esters Using Cs₂CO₃ as Oxygen Source

An effective method for the construction of esters from acyl chloride and halohydrocarbon using Cs₂CO₃ as an oxygen source was achieved for the first time. The methodology has a wide scope of substrates and can be scaled up. The study of a preliminary reaction mechanism demonstrated that the O in the products comes from Cs₂CO₃ and this esterification proceeds through a free radical reaction. It was also found that CO₂ can also be used in this esterification reaction as an oxygen source

Iron/ABNO-Catalyzed Aerobic Oxidation of Alcohols to Aldehydes and Ketones under Ambient Atmosphere

We report a new Fe­(NO₃)₃·9H₂O/9-azabicyclo­[3.3.1]­nonan-<i>N</i>-oxyl catalyst system that enables efficient aerobic oxidation of a broad range of primary and secondary alcohols to the corresponding aldehydes and ketones at room temperature with ambient air as the oxidant. The catalyst system exhibits excellent activity and selectivity for primary aliphatic alcohol oxidation. This procedure can also be scaled up. Kinetic analysis demonstrates that C–H bond cleavage is the rate-determining step and that cationic species are involved in the reaction

Asymmetric Epoxidation of Olefins with Hydrogen Peroxide by an in Situ-Formed Manganese Complex

Asymmetric epoxidation of a variety of cis, trans, terminal, and trisubstituted olefins in excellent yields (up to 94%) and enantioselectivities (>99% ee) by an in situ-formed manganese complex using H₂O₂ has been developed. A relationship between the hydrophobicity of the catalyst imposed by ligand and the catalytic activity has been observed. The influence of the amount and identity of the acid additive was examined, and improved enantioselectivities were achieved through the use of a catalytic amount of a carboxylic acid additive