A direct palladium-catalyzed γ-lactonization of free carboxylic acids via C–O reductive elimination as a key step is described. Notable aspects of this protocol include the use of convenient and easily available sodium percarbonate as an oxidant and the development of a highly efficient β-alanine-derived ligand. The reported method enables the functionalization of a wide range of aliphatic acids including previously inaccessible β-non-quaternary acids. The regioselectivity and consequently substrate scope of this protocol proved complementary to established routes for the direct lactonization of aliphatic carboxylic acids. Through this report, a valuable compound library of γ-lactones with potential applications in various fields has become available.
Xu et al. (Thu,) studied this question.