Polysubstituted (hetero)aromatic compounds play a crucial role in diverse fields, particularly in pharmaceuticals. Approved drugs such as Netupitant, Esomeprazole, Pyridoxine, and Opicapone contain benzene and pyridine rings with more than three substituents (Figure ). To synthesize these compounds, researchers have developed multiple methods, including coupling reactions, C-H functionalization, and cyclization reactions. Single-carbon insertion offers an alternative approach for synthesizing polysubstituted (hetero)aromatic compounds, gaining prominence in the realm of skeletal editing within synthetic organic chemistry. This method significantly alters the structure of the parent skeletons. A common technique for single-carbon insertion involves the reaction of halogenated carbene-equivalents, specifically carbynyl cations, with cyclic compounds (Figure , top). A classic example of this approach is the Ciamician-Dennstedt rearrangement, which transforms pyrrole into pyridine using dichlorocarbene as a carbon source and KO t Bu as a base. Recently, Xu and co-workers introduced a similar reaction using 1,1-dibromoalkane derivatives and LiO t Bu to incorporate diverse functional groups. Carbenoids stabilized by N2-groups have also been employed as a carbon source in this reaction manifold. Bonge-Hansen and co-workers reported the transformation of indoles to quinolines using α-halo-ethyl diazoacetate (α-halo-EDA) in the presence of a Rh catalyst. Levin and co-workers developed a robust ring expansion reaction for pyrrole-and indole-derivatives using αchlorodiazirines as a carbon source, demonstrating an excellent substrate scope. While this reaction is limited to benzylic carbon insertion, the use of α-chlorodiazirines allows for carbon insertion without necessitating potent bases or transition metal catalysts, proving highly advantageous for late-stage functionalization. As a mechanistically distinct reaction, Glorius and co-workers recently reported a ring expansion reaction of indenes under light irradiation using a hypervalent iodine reagent as a carbon source, with a proposed carbynyl radical as the reaction intermediate (Figure , bottom). Despite the rapid growth of the single-carbon insertion methodology for synthesizing (hetero)aromatic compounds, controlling the insertion position remains a significant challenge. For instance, ring expansion of pyrrole to pyridine is solely reported for meta-insertion, where a carbon atom is inserted into the meta-position of a nitrogen atom. Levin and co-workers observed rare para-insertion as a minor product in the reaction of α-chlorodiazirines and a pyrrole derivative. Their density functional theory (DFT) simulation revealed that para-insertion is less favored than meta-insertion due to the high energy barrier (ΔG ‡ > 26 kcal mol -1 ) from transannular cyclopropane to azabenzvalene, a crucial intermediate for the carbon-atom migration step (Figure , top). In other words, the high energy required for the carbon-atom migration step limits the scope of insertion positions. We hypothesized that carbon migration might proceed with lower activation energy via a radical cation intermediate owing to destabilization and bond-weakening resulting from the removal of an electron from the bonding orbital. Consequently, the C-C bond of the cyclopropane ring cleaves to generate a distonic radical cation as an intermediate instead of azabenzvalene under ambient conditions, thereby introducing the potential for unprecedented selectivity in carbon-insertion reactions (Figure , bottom).