Synthesis of Chromones with Methylene-Bridged Carbon Substituent via Annulation of o-Hydroxyaryl Enaminones.

The synthesis of methylene-bridged cyclic compounds, including 3-arylalkyl chromones and methylene-bridged bis-chromones, and methylene-bridged bis-cyclic compounds such as indole, coumarin, and pyranone has been realized with rongalite under catalyst-free or simple iodine-mediated conditions. The simple method provides facile accesses to new methylene-bridged scaffolds and discloses expanded application of rongalite in the synthesis of methylene-bridged organic molecules.