A tandem palladium-catalyzed Heck-lactonization through the reaction of ortho-iodophenols with β-substituted acrylates: synthesis of 4,6-substituted coumarins

Coumarins were obtained in one pot through a palladium-catalyzed Heck-lactonization reaction involving ortho -iodophenols and methyl crotonate or a Z -enoate derived from d -mannitol. These reactions were investigated under different conditions and palladium sources. In the more interesting cases, coumarins were prepared in water, using triethylamine as base and 1 mol % of PdCl 2 as catalyst.