Diatomic-Swap-Enabled Skeletal Editing of Phospha-2-pyrones via [4 + 2] Cycloaddition for the Divergent Synthesis of Phthalates and Pyridines

Diatomic-swap-enabled skeletal editing was demonstrated for the formation of structurally diverse phthalate and pyridine derivatives through [4 + 2] annulations of phospha-2-pyrones with dimethyl acetylenedicarboxylate (DMAD) and p-toluenesulfonyl cyanide (TsCN), the latter proceeding with complete regioselectivity. The present reaction proceeds through a formal diatomic-swap process in which an embedded P–O unit of phospha-2-pyrone is replaced by C–C or C–N fragments. The resulting pyridines are readily diversified through nucleophilic substitution. This work establishes phospha-2-pyrones as versatile and straightforword skeletal editing platforms for the rapid synthesis of phthalate and pyridine scaffolds.