Iridium-catalyzed oxidative lactonization and intramolecular Tishchenko reaction of delta-ketoaldehydes for the synthesis of isocoumarins and 3,4-dihydroisocoumarins.

Two new cyclizations of ketoaldehydes have been developed using an Ir-ligand bifunctional catalyst. Oxidative lactonization of delta-ketoaldehydes proceeded smoothly at room temperature to give coumarin derivatives in excellent yields. Intramolecular Tishchenko reaction of delta-ketoaldehydes afforded 3,4-dihydroisocoumarins in good yields.