Asymmetric synthesis of atropisomers enabled by N-heterocyclic carbene catalysis

The research of atropisomerism in synthetic chemistry has drawn growing attention in recent years, owing to its prevalence and importance to natural products, material science and pharmaceutical chemistry. N-Heterocyclic carbene (NHC)-catalyzed reactions for atropisomer construction has emerged as a burgeoning and promising research topic in recent years. This review mainly summarizes the examples for access to atropisomers catalyzed by NHC catalysis, along with the introduction for NHC precursors and patterns of atropisomers involved. To help understanding the progress of NHC-catalyzed atropisomer construction, this review has been documented according to the following four different strategies: annulation, kinetic resolutions, asymmetric desymmetrizations and central-to-axial chirality conversions. Novel methods for NHC-catalyzed atroposelective synthesis are therefore encouraged, including application of novel NHC intermediates and catalytic modes, in the very near future.