Enantio‐ and Diastereoselective, Lewis Base Catalyzed, Cascade Sulfenoacetalization of Alkenyl Aldehydes

Abstract

Ac atalytic, enantio-, and diastereoselective formation of sulfenyl acetals bearing multiple stereogenic centers is reported. Alkenyl aldehydes undergo ac hiral thiiranium ion initiated cascade starting with intramolecular capture by aformyl group and termination by capture with HFIP solvent. This method provides aone-pot synthesis of dihydropyran and 1,3-disubstituted isochroman acetals in good to excellent yield and with high levels of diastereo-(up to > 99:1 dr) and enantiocontrol (up to 99:1 er).

Recent Advances in Catalytic Asymmetric Syntheses of Functionalized Heterocycles via Halogenation/Chalcogenation of Carbon‐Carbon Unsaturated Bonds

“…Later on, Denmark and co‐workers disclosed an elegant cascade sulfenoacetalization involving intramolecular opening of chiral thiiranium ion by a formyl group and intermolecular capture of oxocarbenium ion with HFIP catalyzed by BINAM‐based phosphoramide catalyst 18 (Scheme 29). [46] This methodology worked well with a variety of alkenyl aldehydes 63 under very mild conditions, and the corresponding sulfenyl acetals 64 bearing multiple stereogenic centers were afforded in good to excellent yields (45–92%) and with high diastereoselectivities (up to >99:1 dr) and enantioselectivities (up to 98% ee).…”