Deaminative Ring Contraction for the Modular Synthesis of Pyrido[ n ]helicenes

A modular strategy involving tertiary amines as templates to build multiple carbon-carbon bonds via reductive cyclization and deaminative contraction steps enables the scalable synthesis of (di)aza[5]helicenes and (di)aza[6]helicenes. The methods permit the rapid and gram-scale assembly of key pyridyl-containing dihydroazepines that are advanced using a developed deaminative contraction to access the N-atom positional isomers of pyrido[5] and [6]helicenes. A telescoped synthesis demonstrates expedited access to (±)-1-aza[6]helicene, a resolvable helicene valued for its circularly polarized luminescence properties.