p-tert-Butylcalix[8]arene: An Effective Nano-ranged Organocatalyst for the Syntheses of Xanthenes and Acridines

This is the first report on the organocatalytic activity of simple unsubstituted p-tertbutylcalix[ 8]arene, C8 towards multi-ring heterocycles. We thereby account an expeditious, ecofriendly, high throughput procedure of the synthesis of some biologically active cores xanthenes and acridines along with spiro-derivatives of both with the aid of the organocatalyst C8. The catalyst is recyclable for at least six cycles without substantial loss of activity.