First tandem nucleophilic addition–electrophilic amination reaction of Eschenmoser’s salts: synthesis of cyclic and spiro-fused hydrazonium salts

A series of cyclic and spiro-fused hydrazonium salts was prepared by tandem nucleophilic addition–electrophilic amination reactions. The method presented makes use of Eschenmoser’s salt or benzotriazole aminals and 2-hydroxylamino-4,5-dihydroimidazolium-O-sulfonate. The products structures were determined by X-ray analysis.