A Three-Component Coupling Strategy for Tetrahydrofuran Synthesis: Application of the Diisopropyl Tartrate Modified (E)-γ-(Dimethylphenylsilyl)allylboronate as an α,γ-Allyl Dianion Equivalent

[reaction: see text] A highly convergent three-component coupling strategy for the stereocontrolled synthesis of 2,3,5-trisubstituted tetrahydrofurans is described. After allylboration of the first aldehyde with 1, the chiral, nonracemic allylsilanes 2 are coupled with a second aldehyde or ketone with Lewis acid catalysis to give tetrahydrofurans 3 or 4 with excellent selectivity. The 2,5-stereochemistry is controlled by operating under nonchelate (e.g., 3) or chelate (e.g., 4) conditions.