title: Osmium(III) and osmium(V) complexes bearing a macrocyclic ligand: a simple and efficient catalytic system for cis-dihydroxylation of alkenes with hydrogen peroxide.
abstract: A simple protocol that uses [Os(III)(OH)(H2O)(L-N4Me2)](PF6)2 (1; L-N4Me2 = N,N'-dimethyl-2,11-diaza[3.3](2,6)pyridinophane) as a catalyst and H2O2 as a terminal oxidant for efficient cis-1,2-dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron-withdrawing groups are selectively oxidized to the corresponding vicinal diols in good to excellent yields (46-99 %). In the catalytic reactions, the stoichiometry of alkene:H2O2 is 1:1, and thus the oxidant efficiency is very high. For the dihydroxylation of cyclohexene, the catalytic amount of 1 can be reduced to 0.01 mol % to achieve a very high turnover number of 5500. The active oxidant is identified as the Os(V)(O)(OH) species (2), which is formed via the hydroperoxide adduct, an Os(III)(OOH) species. The active oxidant 2 is successfully isolated and crystallographically characterized.
authors: Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. sugimoto@mls.eng.osaka-u.ac.jp
authors: Hideki
authors: H
authors: Sugimoto
authors: Kenji
authors: K
authors: Ashikari
authors: Shinobu
authors: S
authors: Itoh
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006900:Hydroxylation; D007536:Isomerism; D008024:Ligands; D047028:Macrocyclic Compounds / Q000737:chemistry*; D008968:Molecular Conformation; D009992:Osmium / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: D000475:Alkenes; D056831:Coordination Complexes; D008024:Ligands; D047028:Macrocyclic Compounds; D009992:Osmium; D006861:Hydrogen Peroxide
keywords: OO activation; alkenes; dihydroxylation; homogeneous catalysis; osmium