A novel access to indole-3-substituted dihydrocoumarins in artificial sweetener saccharin based functional ionic liquids

Abstract

An efficient new multicomponent protocol for the C-3 functionalization of indoles with dihydrocoumarin has been developed using an artificial sweetener (saccharin)-based functional ionic liquid (imidazolium saccharinate). The reaction consists of the Knoevenagel coupling of salicylaldehyde and Meldrum's acid followed by a Michael type reaction with indole, resulting in concomitant lactonization via decarboxylative elimination to yield indole-3-dihydro-coumarins in good to excellent yields at room temperature.