Dichlororuthenium(IV) complex of meso-tetrakis(2,6-dichlorophenyl)porphyrin: active and robust catalyst for highly selective oxidation of arenes, unsaturated steroids, and electron-deficient alkenes by using 2,6-dichloropyridine N-oxide.
[Ru(IV)(2,6-Cl2tpp)Cl2], prepared in 90 % yield from the reaction of [Ru(VI)(2,6-Cl2tpp)O2] with Me3SiCl and structurally characterized by X-ray crystallography, is markedly superior to [Ru(IV)(tmp)Cl2], [Ru(IV)(ttp)Cl2], and [Ru(II)(por)(CO)] (por=2,6-Cl2tpp, F20-tpp, F28-tpp) as a catalyst for alkene epoxidation with 2,6-Cl2pyNO (2,6-Cl2tpp=meso-tetrakis(2,6-dichlorophenyl)porphyrinato dianion; tmp=meso-tetramesitylporphyrinato dianion; ttp=meso-tetrakis(p-tolyl)porphyrinato dianion; F20-tpp=meso-tetrakis(pentafluorophenyl)porphyrinato dianion; F28-tpp=2,3,7,8,12,13,17,18-octafluoro-5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato dianion). The "[Ru(IV)(2,6-Cl2tpp)Cl2]+2,6-Cl2pyNO" protocol oxidized, under acid-free conditions, a wide variety of hydrocarbons including 1) cycloalkenes, conjugated enynes, electron-deficient alkenes (to afford epoxides), 2) arenes (to afford quinones), and 3) Delta5-unsaturated steroids, Delta4-3-ketosteroids, and estratetraene derivatives (to afford epoxide/ketone derivatives of steroids) in up to 99 % product yield within several hours with up to 100 % substrate conversion and excellent regio- or diastereoselectivity. Catalyst [Ru(IV)(2,6-Cl2tpp)Cl2] is remarkably active and robust toward the above oxidation reactions, and turnover numbers of up to 6.4x10(3), 2.0x10(4), and 1.6x10(4) were obtained for the oxidation of alpha,beta-unsaturated ketones, arenes, and Delta5-unsaturated steroids, respectively.
Zhang
Jun-Long
JL
Department of Chemistry and Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong, Pokfulam Road, Hong Kong.
Che
Chi-Ming
CM
D000475:Alkenes / Q000737:chemistry*; D001554:Benzene / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D004583:Electrons; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D017975:Ruthenium Compounds / Q000737:chemistry*; D013256:Steroids / Q000737:chemistry*
C512313:2,6-dichloropyridine N-oxide; D000475:Alkenes; D008024:Ligands; D010087:Oxides; D011166:Porphyrins; D011725:Pyridines; D017975:Ruthenium Compounds; D013256:Steroids; D001554:Benzene