Unsymmetrical Difunctionalization of Two Different C-H Bonds in One Pot under Transition-Metal Catalysis

Recent advancements in unsymmetrical difunctionalization based on the substitution of two different C-H bonds in one-pot are described. Due to the difficulty of controlling reactivity and selectivity, multi-functionalization via substitution of several C-H bonds to install different functional groups has been limited until recently, in comparison with well-studied functionalization via sequential addition to unsaturated π-bonds. This difunctionalization protocol provides an efficient and rapid approach to a library of structurally complicated target molecules through the formation of multiple C-X bonds with high atom- and step-economy. 1 Introduction 2 ortho -Selective Functionalization of Two Different C-H Bonds Relative to the Directing Group 2.1 Unsymmetrical Difunctionalization with the Introduction of Similar Functional Groups 2.2 Unsymmetrical Difunctionalization with the Introduction of Different Functional Groups 2.3 ortho -Selective Unsymmetrical Difunctionalization Promoted by Two Different Directing Groups Appearing During the Progress of the Reaction 3 ortho / meta -Selective C-H Bond Difunctionalization Relative to the Directing Group 4 Sequential Difunctionalization of Fused Aromatic Compounds and Heterocycles 5 Summary and Outlook.