N-Heterocyclic Carbene-Catalyzed Atroposelective Annulation for Access to Thiazine Derivatives with C-N Axial Chirality

Abstract

A catalytic atroposelective cycloaddition reaction between thioureas and ynals is developed. This reaction features the first NHC-catalyzed addition of thioureas to acetylenic acylazolium intermediates to eventually set up C-N axial chirality with excellent optical purities. The obtained axially chiral thiazine derivative products bear multiple functional groups and are feasible for further transformations.

Keywords: N-heterocyclic carbenes; atroposelective reaction; chiral C−N axis; organocatalysis.