Regioselective C−H Functionalization of Heteroarene N ‐Oxides Enabled by a Traceless Nucleophile

Although N‐alkenoxyheteroarenium salts have been widely used as umpoled synthons with nucleophilic (hetero)arenes, the use of electron‐poor heteroarenes has remained unexplored. To overcome the inherent electron deficiency of quinolinium salts, a traceless nucleophile‐triggered strategy was designed, wherein the quinolinium segment is converted into a dearomatized intermediate, thereby allowing simultaneous C8‐functionalization of quinolines at room temperature. Experimental and computational studies support the traceless operation of a nucleophile, which enables the previously inaccessible transformation of N‐alkenoxyheteroarenium salts. Remarkably, the generality of this strategy has been further demonstrated by broad applications in the regioselective C−H functionalization of other electron‐deficient heteroarenes such as phenanthridine, isoquinoline, and pyridine N‐oxides, offering a practical tool for the late‐stage functionalization of complex biorelevant molecules.