A new route to indolines by the Cu-catalyzed cyclization reaction of 2-ethynylanilines with sulfonyl azides

It is revealed that 2-sulfonyliminoindolines can be efficiently synthesized by the Cu-catalyzed cyclization reaction of N-alkyl- or aryl-substituted 2-ethynylanilines with sulfonyl azides. This new route to the indoline derivatives is characterized by mild reaction conditions, facile introduction of functional groups at the 2-poiltion of the indoline ring, and the wide substrate scope. Selective transformation of indoline to oxindole and isatin analogs is also demonstrated.