Catalytic, Enantioselective Hydrogenation of Heteroaromatic Compounds

Enantioselective catalytic hydrogenation of heteroarenes provides straightforward, atom‐economical access to the corresponding cyclic heterocycles, which are found as common structural motifs in many important biologically active reagents and alkaloids. This enantioselective transformation has developed only recently due to the high stability of these aromatic compounds and the poisoning effects of nitrogen or sulfur atoms to chiral catalysts. Moreover, heteroarenes comprise a very large family with diverse structural features and each type of heteroarene substrate shows distinct reactivity in hydrogenation. Various heteroarenes, including quinolines, isoquinolines, quinoxalines, pyridines, indoles, pyrroles, imidazoles, oxazoles, and furans, can be smoothly hydrogenated with good to excellent enantioselectivity under proper reaction conditions. Transition‐metal catalysts, based on iridium, ruthenium, rhodium, and palladium complexes, play an important role in this field, and organocatalysts have also shown high efficiency for hydrogenation of certain heteroarenes. This chapter provides a comprehensive analysis that includes the advantages of a given catalyst system for each type of substrate. Some total syntheses that feature enantioselective hydrogenation of heteroaromatics as key steps are also described in this chapter.