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.

Automated summary

A catalyst-free [1+2+3] cycloaddition/N-N bond cleavage sequential reaction was developed to access spiroindolines with syn-stereoselectivity by utilizing an underexplored reaction mode of C,N-cyclic azomethine imines. Experimental results and DFT calculations identified peroxide and ethereal solvent as triggers for the reaction, initiating hydrogen abstraction and subsequent N-N bond cleavage.