Spiro‐ and Bicycloannulation of Sulfoximine‐Substituted 2‐Hydroxy‐dihydropyrans: Enantioselective Synthesis of Spiroketals, Spiroethers, and Oxabicycles and Structure of Dihydropyran Oxocarbenium Ions - Lejkowski - 2014 - European Journal of Organic ...