Aerobic organocatalytic oxidation is an important goal for chemical synthesis due to its outstanding advantages compared to traditional oxidative methodologies. The aerobic epoxidation of alkenes, in particular, has attracted remarkable attention within the last decade, since it produces valuable and important intermediates for fine chemical synthesis. Bio-inspired flavin organocatalysts mimic the active site of many flavin-containing monooxygenases and are able to conduct aerobic oxidation of sulfides, amines, cyclobutanones and aryl aldehydes with the help of a stoichiometric reducing partner. In this study, the chemistry of redox active flavin organocatalysts was extended to the activation of O2 and epoxidation of a,�-unsaturated aldehydes. Using flavin catalysts for O2 activation, prolinol co-catalysts for chiral induction, benzothiazoline as a stoichiometric reductant and oxygen as the stoichiometric oxidant, the epoxidation of enals was achieved with good yields, excellent diastereoselectivity and enantioselectivity. To understand the mechanism of aerobic epoxidation, kinetic studies were preformed to understand the role of flavin organocatalysts in this metal free aerobic oxidation system.

Bio-inspired aerobic asymmetric epoxidation of a,�-unsaturated aldehydes: A flavin catalyzed hydrogen peroxide generation/epoxidation sequence

246th National Meeting (2013)

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