Annulation of 1H-pyrrole-2,3-diones by thioacetamide: an approach to 5-azaisatins.

A novel approach to 1H-pyrrolo[3,2-c]pyridine-2,3-diones (5-azaisatins) has been developed via an unprecedented annulation of pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones by thioacetamide. A new way of C-H functionalization of thioacetamide has been discovered. The reaction proceeds under green catalyst-free conditions.