Regioselective Synthesis of 4,5‐Dihydro‐6H‐oxepino[3,2‐c]chromene‐2,6(3H)‐diones through Palladium‐Catalyzed Intramolecular Alkoxycarbonylation of 3‐Allyl‐4‐hydroxycoumarins.

Seven‐membered ring lactones fused to coumarin scaffolds were obtained via a palladium‐catalyzed regioselective intramolecular alkoxycarbonylation under a CO atmosphere. Cyclocarbonylation of 3‐allyl‐4‐hydroxycoumarin derivatives was accessed in the absence of hydrogen gas, acidic conditions, or any other additives. The results of the control experiments revealed the importance of pKa of the substrate for initiating the reaction. [ABSTRACT FROM AUTHOR]