Mononuclear Non-Heme Manganese-Catalyzed Enantioselective cis -Dihydroxylation of Alkenes Modeling Rieske Dioxygenases.

The practical catalytic enantioselective cis -dihydroxylation of olefins that utilize earth-abundant first-row transition metal catalysts under environmentally friendly conditions is an important yet challenging task. Inspired by the cis -dihydroxylation reactions catalyzed by Rieske dioxygenases and non-heme iron models, we report the biologically inspired cis -dihydroxylation catalysis that employs an inexpensive and readily available mononuclear non-heme manganese complex bearing a tetradentate nitrogen-donor ligand and aqueous hydrogen peroxide (H 2 O 2 ) and potassium peroxymonosulfate (KHSO 5 ) as terminal oxidants. A wide range of olefins are efficiently oxidized to enantioenriched cis -diols in practically useful yields with excellent cis -dihydroxylation selectivity and enantioselectivity (up to 99% ee). Mechanistic studies, such as isotopically 18 O-labeled water experiments, and density functional theory (DFT) calculations support that a manganese(V)-oxo-hydroxo (HO-Mn V ═O) species, which is formed via the water-assisted heterolytic O-O bond cleavage of putative manganese(III)-hydroperoxide and manganese(III)-peroxysulfate precursors, is the active oxidant that effects the cis -dihydroxylation of olefins; this is reminiscent of the frequently postulated iron(V)-oxo-hydroxo (HO-Fe V ═O) species in the catalytic arene and alkene cis -dihydroxylation reactions by Rieske dioxygenases and synthetic non-heme iron models. Further, DFT calculations for the mechanism of the HO-Mn V ═O-mediated enantioselective cis -dihydroxylation of olefins reveal that the first oxo attack step controls the enantioselectivity, which exhibits a high preference for cis -dihydroxylation over epoxidation. In this study, we are able to replicate both the catalytic function and the key chemical principles of Rieske dioxygenases in mononuclear non-heme manganese-catalyzed enantioselective cis -dihydroxylation of olefins.