Synthesis of N-(Isoquinolin-1-yl)sulfonamides via Ag2O-Catalyzed Tandem Reaction of ortho-Alkynylbenzaldoximes with Benchtop Stabilized Ketenimines.

In this project, a moderately efficient approach to multisubstituted N-(isoquinolin-1-yl)sulfonamide derivatives was illustrated, utilizing ortho-alkynylbenzaldoximes and zwitterionic ketenimine salts in a tandem reaction catalyzed by silver oxide. The oxophilicity of Ag2O, along with its nature as Lewis acid, pave the way for a smooth [3 + 2] cycloaddition between isoquinoline N-oxides and ketenimine species, which is a key step in this reaction. DFT calculation suggests that 1,3-dipolar cycloaddition of nitrone and ketenimine proceeds through a selective stepwise mechanism.