8.29 Reduction of Epoxides

Abstract

The transformation of epoxides into other compounds by exploiting the reactivity of the oxirane ring has emerged as a powerful tool in organic synthesis. Moreover, the rapid development of efficient and practical methods for the preparation of epoxides in enantiopure form has encouraged chemists to make such transformations easy to carry out, chemo-, regio-, and stereoselective, as well as of general applicability. This chapter describes reductions of the epoxides grouped in two different types: (1) reduction to alcohols and (2) deoxygenation to alkenes. It focuses on reactions that allow the preparation of alcohols by reductive ring opening of epoxides with particular emphasis on synthetic methods that are regioselective and stereoselective, compatible with other functional groups, and that have been used in the preparation of useful target molecules. The deoxygenation of epoxides, which may be seen as masked or protected forms of alkenes, is another important method that is useful for the preparation of functionalized alkenes of interest in organic synthesis in general and in medicinal chemistry in particular. Relevant advances in these fields since the first edition of comprehensive organic synthesis in 1991 are reported; older but still used methods will also be mentioned.