Isocoumarin Synthesis via Metal-Free C-Arylation of Acetoacetates with ortho-Ester-Functionalized Diaryliodonium Salts

In this study, a metal-free approach was developed for the synthesis of isocoumarin frameworks by exploiting the reactivity between ortho-carboxylate-ester-substituted diaryliodonium salts and acetoacetates. This transformation involved the sequential C-arylation of an activated methylene substrate, followed by in situ enolization and intramolecular lactonization to construct an isocoumarin core. Under operationally simple conditions, a range of diaryliodonium salts and acetoacetate esters were employed to afford structurally diverse isocoumarins. The resulting products contained synthetically valuable functional groups, including halogen, nitro, carboxylate ester, and azide substituents, which facilitated further derivatization and extension toward complex architectures and potential applications. Subsequent transformation of the selected isocoumarin products enabled the synthesis of furo[3,4-c]isochromene-1,5-dione motifs, which are observed in several natural products.