The Emergence of Palladium-Catalyzed C(sp )-H Functionalization of Free Carboxylic Acids.

Palladium-catalyzed directing group assisted C-H bond activation has emerged as a powerful tool in synthetic organic chemistry. However, only recently, among various directing groups, widely available carboxylate moiety is recognized as a versatile candidate for the regioselective transformations. Notably, palladium-catalyzed carboxylate directed C(sp )-H bond activation and diverse functionalization is highly challenging and has gained huge attention for its versatile applications. Mono- and bidentate ligands have proven to be useful for accelerating the C(sp )-H bond activation step, which helps to control reactivity and selectivity (including enantioselectivity). In this Minireview, we discuss the recent progress made in palladium-catalyzed C(sp )-H bond functionalization reactions for the construction of C-C and C-Heteroatom bonds with the direction of free carboxylic acid.