cis-Dihydroxylation and Epoxidation of Alkenes by [Mn_2O(RCO_2)_2(tmtacn)_2]:Tailoring the Selectivity of a Highly H_2O_2-Efficient Catalyst

摘要

cis-Dihydroxylation and epoxidation of alkenes are key chemical transformations in synthetic organic chemistry,for which both stoichiometric oxidants (e.g.,peracids,MnO_4~-,OsO_4) and second-and third-row transition metal-based oxidation catalysts have proven to be very effective.In recent years,considerable advances have been made in the development of atom-efficient and environmentally friendly catalytic methods employing H_2O_2,most notably in the use of Mn~(II) salts~4 and Fe~(II) complexes in the catalytic epoxidation of alkenes.In contrast,first-row transition metal-catalyzed cis-dihydroxylation of alkenes remains a considerable challenge.Nevertheless,the recent report by De Vos et al.with heterogenized Mn-tmtacn,Que et al.with Fe~(II) pyridyl-amine-based complexes,and our results on the use of the oxidation catalyst [Mn~(IV)_2O_3(tmtacn)_2]~(2+) (1),in the presence of electron deficient aldehydes,demonstrate the potential of these metals toward cis-dihydroxylation.