Transition Metals-Catalyzed Green Oxidation Of Alkynes

Transition metal catalyzed green oxidations of alkynes are included in this thesis, which is composed with two parts as follows:1. Wacker-Type Oxidation of Alkynes into 1,2-Diketones Using Molecular OxygenIn this section, we describe an intriguing new Wacker-type oxidation of alkynes catalyzed by PdBr2 and CuBr2, which opens an efficient access to 1,2-diketones using molecular oxygen as the ultimate oxidant. Under the optimized conditions, a variety of alkynes bearing a wide range of functional groups, including diarylalkynes, arylalkylalkynes and dialkylalkynes, were compatible substrates in this transformation. Based upon experimental observations and literatures, a plausible mechanism, involving sequential attacks of water molecules, was proposed. A better understanding of the experimental observations was achieved by DFT calculations.2. Ruthenium-Catalyzed Alkynes Oxidation with Part-per-Million Catalyst LoadingsThe combination of [Ru(cymene)Cl2]2, I2 and TBHP affords an efficient catalytic system for the green oxidation of a variety of alkynes, giving the corresponding 1,2-diketones in high to excellent yields. Two noteworthy features of the method are extremely high catalyst productivity (TON up to 420 000) and scale-up to 1 mol, thus implying the feasibility of industrial/practical applications. Importantly, no residual ruthenium impurity was detected by ICP mass analysis in the 1,2-diketone products after recrystallization or column chromatography purification. Based upon 13C NMR and 18O labeling experiments, formation of iodonium ion and water as reagent were proposed in the catalytic cycle.