Deaminative ring contraction for the modular synthesis of pyrido[n]helicenes

A modular strategy involving the use of 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 pyridyl-containing biaryl-linked dihydro-azepines as key intermediates that are advanced using a developed deaminative contraction reaction to access N-atom positional isomers of pyrido[5] and [6]helicenes. A telescoped synthesis that foregoes the purification of biaryl-linked dihydroazepines intermediates demonstrates expedited access to (±)-1-aza[6]helicene, a resolvable helicene valued for its circularly polarized luminescence properties.