Homogeneous [RuIII(Me3tacn)Cl3]-catalyzed alkene cis-dihydroxylation with aqueous hydrogen peroxide

A simple and green method that uses [Ru(Me₃tacn)Cl₃] (1; Me₃tacn=N,N′,N″-trimethyl-1,4,7-triazacyclononane) as catalyst,aqueous H₂O₂ as the terminal oxidant, and Al₂O₃ and NaCl as additives is effective in the cis-dihydroxylation of alkenes in aqueous tert-butanol. Unfunctionalized alkenes,including cycloalkenes, aliphat ic alkenes, and styrenes (14 examples) were selectively oxidized to their corresponding cis-diols in good to excellent yield (70-96%) based on substrate conversions of up to 100%. The preparation of cis-1,2-cycloheptanediol (119 g,91 % yield) and cis-1,2-cyclooctanediol (128 g,92 % yield) from cycloheptene and cyclooctene,respectively, on the 1-mol scale can be achieved by scaling up the reaction without modification. Results from Hammett correlation studies on the competitive oxidation of para-substituted styrenes (ρ=-0.97, R=0.988) and the detection of the cycloadduct [(Me ₃tacn)ClRuHO₂(C₈H₁₄)]⁺ by ESI-MS for the 1-catalyzed oxidation of cyclooctene to cis-1,2-cyclooctanediol are similar to those of the stoichiometric oxidation of alkenes by cis-[(Me ₃tacn)-(CF₃CO₂)Ru^VIO₂]+ through [3+2] cycloaddition (W.-P. Yip, W .-Y. Yu, N. Zhu, C.-M. Che, J. Am. Chem. Soc. 2005, 127,14239). © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.