Syn -Stereoselective C3-Spirocyclization and C2-Amination of 3-(2-Isocyanoethyl)indole Using C , N -Cyclic Azomethine Imines.

By utilizing an underexplored reaction mode of C , N -cyclic azomethine imines, a catalyst-free [1+2+3] cycloaddition/N-N bond cleavage sequential reaction for accessing spiroindolines with syn -stereoselectivity was developed. On the basis of experimental results and DFT calculations, peroxide and ethereal solvent were identified to trigger the hydrogen abstraction of the unstable [1+2+3] cycloaddition adducts, followed by homolytic cleavage of the N-N bond and hydrogen absorption.