Boron-mediated synthesis of phthalides

Phthalides represent a privileged class of γ-heterocyclic lactones with significant biological activity and industrial utility.Despite their importance, the modular construction of highly functionalized phthalides typically requires transition-metal catalysts or sensitive organometallic precursors.We report a transition-metal-free, boron-mediated tandem aldolization-transesterification protocol for the divergent synthesis of C3-functionalized phthalides.By leveraging the unique Lewis acidity and oxophilicity of trivalent boron, methyl 2formylbenzoate is reacted with a broad array of bis-boron enediolates derived from carboxylic acids to furnish target heterocycles in generally excellent yields and high diastereoselectivities.γ-Heterocyclic lactones constitute fundamental architectural cornerstones in natural product biosynthesis and contemporary medicinal chemistry.[1][2][3] Within this class, the α,β-unsaturated butenolide moiety is a preeminent privileged motif, underpinning the bioactivity of diverse entities