Stereoselective Synthesis of Polysubstituted Tetrahydropyranones via Acid-Promoted Cyclization of β-Silyl-γ-ethylidene-γ-butyrolactones with Aldehydes and Ketones.

β-Silyl-γ-ethylidene-γ-butyrolactone upon one-pot treatment with aldehydes and ketones in the presence of Lewis acids underwent a tandem Hosomi-Sakurai/Prins cyclization to give polysubstituted tetrahydropyranones stereoselectively. Various aldehydes and ketones can be used in this reaction to produce the corresponding tetrahydropyranones. The optical purity of the starting γ-butyrolactone was substantially retained in the resulting tetrahydropyranones.

Acid-catalyzed chirality-transferring intramolecular Friedel-Crafts cyclization of α-hydroxy-α-alkenylsilanes.

Acid-catalyzed intramolecular Friedel-Crafts cyclization of optically active α-hydroxy-α-alkenylsilanes possessing a benzene ring (>99% ee) with TMSOTf as a Lewis acid gave enantio-enriched tetrahydronaphthalenes (up to 98% ee). The silyl group attached to the chiral carbon played a crucial role in the chirality transfer.