We herein successfully demonstrate the use of chiral isochalcogenoureas as Lewis Base catalysts for a variety of (4+2)-cycloaddition reactions of allenoates and different Michael acceptors. In all cases the same structural key-motive, a dihydropyran with a (Z)-configurated exocyclic double bond could be accessed as the major regio- and diastereoisomer in an enantioselective manner. Furthermore, these chiral dihydropyrans were successfully engaged in different follow-up transformations.
Keywords: Allenoates; Cycloadditions; Isochal-cogenoureas; Lewis Bases; Organocatalysis.