Enantioselective hydroxylation of benzylic C-H bonds by D-4-symmetric chiral oxoruthenium porphyrins

A D-4-symmetric chiral dioxoruthenium(VI) porphyrin can effect stoichiometr ic and catalytic enantioselective hydroxylation of benzylic C-H bonds to gi ve enantioenriched aryl alcohols, the highest ee of 76% being attained in t he catalytic oxidation of 4-ethyltoluene with 2,6-dichloropyridine N-oxide as terminal oxidant; the oxidations proceed via a rate-limiting H-atom abst raction to germinate a benzylic radical intermediate.