Iridium-catalyzed oxidative lactonization and intramolecular Tishchenko reaction of δ-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 sigma-ketoaldehydes proceeded smoothly at room temperature to give coumarin derivatives in excellent yields. Intramolecular Tishchenko reaction of sigma-ketoaldehydes afforded 3,4-dihydroisocoumarins in good yields. (c) 2005 Elsevier Ltd. All rights reserved.