Enantioselective Synthesis of 3,5,6‐Substituted Dihydropyranones and Dihydropyridinones using Isothiourea‐Mediated Catalysis

The scope of dihydropyranone and dihydropyridinone products accessible by isothiourea‐catalyzed processes has been expanded and explored through the use of 2‐N‐tosyliminoacrylates and 2‐aroylacrylates in a Michael addition‐lactonization/lactamization cascade reaction. Notably, to ensure reproducibility it is essential to use homoanhydrides as ammonium enolate precursors with 2‐aroyl acrylates, while carboxylic acids can be used with 2‐N‐tosyliminoacrylates, delivering a range of 3,5,6‐substituted dihydropyranones and dihydropyridinones with high enantioselectivity (typically >90 % ee). The derivatization of the heterocyclic core of a 3,5,6‐substituted dihydropyranone through hydrogenation is also reported.