cis-Dihydroxylation and Epoxidation of Alkenes by Manganese Catalysts - Selectivity, Reactivity and Mechanism

摘要

Oxidation reactions are among the most elementary of organic transformations and are essential in biology, chemical industry and (synthetic organic) chemistry. Selective oxidation of hydrocarbons, such as cis-dihydroxylation and epoxidation of alkenes, introduces functional groups and yields useful products or intermediates which in turn can be used as building blocks for more complex chemical structures. Despite considerable advances in recent years, major challenges remain in oxidation chemistry. The need for increased atom efficiency demands the use of oxidants, which do not generate stoichiometric amounts of by-products. From an environmental and atom economy perspective, the two most desirable oxidants to use are molecular oxygen (O2) and hydrogen peroxide (H2O2). Selectivity is another key issue. In order to develop a useful process, the introduction of oxygen atom(s) to the substrate should occur only at the desired position(s) in the molecule. Furthermore, the catalyst used to activate the oxidant (O2 or H2O2) should be cheap, non-toxic and robust. This thesis describes both the development of new methods for the selective and environmentally benign cis-dihydroxylation and epoxidation of alkenes and the mechanistic studies of these new processes. Since the catalyst used is based on manganese and hydrogen peroxide is employed as oxidant, this new method is a more environmentally benign alternative for the currently existing technology.