CHAPTER 7: Asymmetric Cross-Dehydrogenative-Coupling Reactions

Asymmetric cross-dehydrogenative-coupling (CDC) reactions provide a means of constructing carbon–carbon bonds directly from two different C–H bonds in an enantioselective manner. These reactions are expected to be extremely useful in terms of cost- and step-economy, since no pre-functionalization of substrates is required. Coupled with in situ oxidative activation of substrates using molecular oxygen, tert-butyl peroxide, hydrogen peroxide, benzoquinone, or 2,3-dichloro-5,6-dicyanobenzoquinone as the oxidant, the use of appropriate chiral catalysts should allow the production of optically active and highly functionalized molecules in a single step. Since asymmetric CDC reactions must be performed under oxidative conditions, the keys to success include the use of chiral catalysts that are robust under such conditions and appropriate oxidants depending on the nature of the substrates. Following the rapid progress in non-asymmetric CDC reactions, development of asymmetric versions has attracted increasing attention, and high levels of asymmetric induction have become feasible in some cases. This chapter will focus on: (1) reactions of α-C–H bonds of nitrogen-containing compounds; (2) reactions of benzylic C–H bonds; (3) functionalization via oxidation of enamine and Breslow intermediates; (4) naphthol coupling reactions; and (5) coupling reactions of arenes with olefins (Fujiwara–Moritani reactions).