Sulfilimines as Versatile Nitrene Transfer Reagents: Facile Access to Diverse Aza‐Heterocycles

We herein report the unprecedented synthesis of diverse biologically important aza‐heterocycles by employing sulfilimines as nitrene transfer reagents. This class of sulfur‐based aza‐ylides had not been successfully used for gold nitrene transfer before. This work contains an efficient generation of α‐imino gold carbenes by N−S cleavage of sulfilimines. These gold carbenes undergo C−H insertion, cyclopropanation, and nucleophilic attack to form indoles (44 examples), 3‐azabicyclo[3.1.0]hexan‐2‐imines (24 examples), and imidazoles (3 examples). Our study represents a unique gold‐catalyzed reaction between alkynes and sulfur ylides, and also includes the first aza‐heterocycle synthesis that proceeds by intermolecular nitrene transfer followed by cyclopropanation of the α‐imino gold carbenes. Moreover, an unexpected synthesis of 4‐acylquinolines (3 examples) from 2‐acylphenyl sulfilimines and propargylic silyl ether derivatives by a 1,2‐hydride shift onto the α‐imino gold carbene and a subsequent Mukaiyama aldol cyclization was discovered. Golden diversity: Readily available sulfilimines were successfully applied as versatile nitrene transfer reagents. By trapping the resulting α‐imino gold carbenes with divergent functionalities, four different types of aza‐heterocycles (indoles, 3‐azabicyclo[3.1.0]hexan‐2‐imines, quinolines, and imidazoles) were prepared in high efficiency.