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

Abstract

[RuIV(2,6-Cl2tpp)Cl2], prepared in 90% yield from the reaction of [RuVI(2,6-Cl2tpp)O2] with Me3SiCl and structurally characterized by X-ray crystallography, is markedly superior to [RuIv(tmp)Cl2], [RuIV(ttp)Cl2], and [RuII(por)(CO)] (por = 2,6-Cl2tpp, F20-tpp, F28-tpp) as a catalyst for alkene epoxidation with 2,6-Cl2pyNO (2,6Cl2tpp = 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-Cl 2pyNO" 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) Δ5-unsaturated steroids, Δ4-3- 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 [RuIv(2,6-Cl2tpp)Cl2] is remarkably active and robust toward the above oxidation reactions, and turnover numbers of up to 6.4 × 103, 2.0 × 104, and 1.6 × 104 were obtained for the oxidation of α,β-unsaturated ketones, arenes, and Δ5-unsaturated steroids, respectively. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.