Dearomatizing [2+2+1] Spiroannulation of Indoles with Alkynes.

ABSTRACT

A palladium-catalyzed dearomatizing [2+2+1] spiroannulation of indoles with two molecular internal alkynes is developed in the presence of Cu(OAc)2/O2 as the oxidant, in which a domino sequence including C-H activation of indole followed by consecutive Heck reactions is involved. A range of 3,3'-spiroindolines bearing tetrasubstituted cyclopentadiene moieties and exocyclic C═C bonds at C2 are obtained in moderate to excellent yields.