Divergent Synthesis of Axially Chiral 2-Pyranones and Fused 2-Pyridones via N-Heterocyclic Carbene-Catalyzed Atroposelective [3 + 3] Annulation

An N-heterocyclic carbene-catalyzed atroposelective [3 + 3] annulation of alkynyl acylazoliums with benzothiazole derivatives has been developed for the divergent synthesis of axially chiral triaryl 2-pyranones and fused 2-pyridones. The regioselectivity of this protocol depends on the structure of benzothiazoles with three different nucleophilic centers. The obtained axially chiral frameworks represent a new class of arylheterocycle atropisomers, which may be potentially useful in medicinal chemistry.