Synthetic Strategies to Control C–N Atropisomerism in Acyclic Amines and Amides

Abstract

AbstractAtropisomeric molecules are a privileged class of stereogenic material that have important applications in catalysis, materials science and medicines. To date, the majority of work has been focused upon biaryl and heterobiaryl scaffolds involving restricted rotation between a pair of cyclic fragments, but C–N atropisomeric molecules based upon amines and amides, where the nitrogen atom is not part of a ring system, are rapidly emerging as an important class of stereogenic molecules. This is the focus of this Short Review, which begins by discussing the factors which influence the configurational stability of such molecules and provides a historical background to their synthesis. This is followed by a detailed discussion of state-of-the-art catalytic asymmetric strategies that are now available to access C–Nacyclic atropisomers including carboxamides, sulfonamides, sulfinamides, phosphamides and diarylamines. A variety of different synthetic approaches are discussed, including kinetic resolution/desymmetrization, amination, C–H functionalization, N-functionalization, and annulation.1 Introduction2 Atropisomerism in Acyclic Amines and Amides3 Synthesis Directed by a Chiral Auxiliary4 Atropselective Synthesis4.1 Kinetic Resolution and Desymmetrization4.2 Electrophilic Amination4.3 C–H Functionalization4.4 N-Functionalization4.5 Annulation5 Conclusions and Outlook