Intramolecular Polar [4⊕+2] Cycloadditions of Aryl‐1‐aza‐2‐azoniaallene Salts: Unprecedented Reactivity Leading to Polycyclic Protonated Azomethine Imines

Charged up: In the first example of the title salts undergoing a [4⊕+2] cycloaddition reaction, the azo bond and one aromatic π bond make up the 4π component. This reaction appears to be concerted and provides high yields of protonated azomethine imine products. Substituted alkenes provided products containing all-carbon or nitrogen-bearing quaternary centers in high yield.