Versatile Oxidation Methods for Organic and Inorganic Substrates Catalyzed by Platinum-Group Metals on Carbons

Effect of distal metal species on lewis basicity of a μ3-oxo ligand in a doubly oxo-bridged (μ3-O)[Rh(cod)]3(μ4-O)M core

The Lewis basicity of a μ3-oxo ligand for (μ3-O)[Rh(cod)]3(μ4-O)M (cod = 1,5-cyclooctadiene) complexes was controllable by metal species on the μ4-oxo ligand locating at the opposite site of the μ3-oxo ligand. Coordination of the μ3-oxo ligand of [(μ3-O){Rh(cod)}3(μ4-O){Au(PPh3)}][BF4] (1) to [Au(PPh3)]+ indicated sufficient Lewis basicity of the μ3-oxo ligand in 1 to form [{(Ph3P)Au}(μ3-O){Rh(cod)}3(μ4-O){Au(PPh3)}][BF4] (2). In contrast, the addition of Li+ to 1 induced elimination of the originally coordinated [Au(PPh3)]+ due to the weak Lewis basicity of the μ3-oxo ligand for (μ3-O){Rh(cod)}3(μ4-O)Li(THF)3, in which a pentanuclear species, [{(Ph3P)Au}(μ3-O){Rh(cod)}3(μ4-O){Li(THF)3}][BF4] (3), was assumed to be generated in situ before the dissociation of [Au(PPh3)]+.

Catalyst-Free and Transition-Metal-Free Approach to 1,2-Diketones via Aerobic Alkyne Oxidation

A catalyst-free and transition-metal-free method for the synthesis of 1,2-diketones from aerobic alkyne oxidation was reported. The oxidation of various internal alkynes, especially more challenging aryl-alkyl acetylenes, proceeded smoothly with inexpensive, easily handled, and commercially available potassium persulfate and an ambient air balloon, achieving the corresponding 1,2-diketones with up to 85% yields. Meanwhile, mechanistic studies indicated a radical process, and the two oxygen atoms in the 1,2-diketons were most likely from persulfate salts and molecular oxygen, respectively, rather than water.

Copper-Catalyzed Aqueous N-O Bond Cleavage of 2-Oxa-3-Azabicyclo Compounds to Cyclic cis-1,4-Amino Alcohols

The N-O bond cleavage of 2-oxa-3-azabicyclo substrates, which are readily prepared by the hetero Diels-Alder reaction between nitroso dienophiles and cyclic 1,3-dienes, was effectively catalyzed by heterogeneous copper-on-carbon (Cu/C) under aqueous conditions to give the corresponding cyclic cis-1,4-amino alcohol derivatives. The present method was applied to the direct incorporation of the hydroxy and amino groups derived from a nitroso substrate into cyclic 1,3-dienes with cis-selectivity by the combination of the in situ formation of 2-oxa-3-azabicyclo compounds and following Cu/C-catalyzed N-O bond cleavage. The obtained cis-4-aminocyclohexenols, derived from cyclohexadiene as a cyclic 1,3-diene, could be selectively oxidized by using the ruthenium-on-carbon (Ru/C) catalyst under oxygen atmosphere to the corresponding 4-aminocyclohexenones at 50-65 °C or para-iminoquinones at 100-110 °C as useful reactive synthetic precursors.

Deposition of tetraferrocenylporphyrins on ITO surfaces for photo-catalytic O2 activation

Tetraferrocenylporphyrins have been successfully deposited on ITO electrodes for O₂ photo-catalytic activation.