Transition Metal Catalyzed Enantioselective α-Heterofunctionalization of Carbonyl Compounds

Advances in the field of asymmetric α-heterofunctionalization of carbonyl compounds, where the enantioselectivity of the process is achieved by the use of chiral transition metal catalysts, are discussed. Studies have shown that metal-catalyzed electrophilic substitution at the α-carbon of a carbonyl compound by heteroatoms, particularly F, O, and N, can be achieved with excellent yields and enantioselectivities. For the α- heterofunctionalization of less acidic carbonyl groups, such as aldehydes and ketones, preactivation of the α-carbon is necessary for metal catalysis and has so far been demonstrated via both enol ethers and metal (tin) enolates. The emergence of proline-derived organocatalysts has enabled asymmetric α-heterofunctionalization of this type of substrate to be achieved in recent years, including fluorination, amination, and oxygenation.