Pyridine C─N Transposition via Cycloaddition–Cycloreversion

The selective incorporation of nitrogen atoms is fundamental to the design and synthesis of drugs and other functional molecules. Here, we describe a skeletal‐editing approach to the transposition of pyridine nitrogen atoms, creating a route to 3‐alkylated pyridines that are difficult to access using current methods. The reaction uses a cycloaddition/cycloreversion strategy (CACR) to transpose easily made 4‐aryl and alkyl pyridines into the more challenging meta ‐functionalized isomers. The cycloaddition reaction introduces versatile sulfone functionality, that can be harnessed for further C─X and C─C bond formations for pyridine synthesis.