Functionalized (E)-crotylsilanes 1 undergo Lewis acid promoted conjugate addition reactions with «-substituted enals and methyl vinyl ketone 2 to produce tetrasubstituted cyclopentanes 3 with high levels of diastereoselection. The reaction is believed to proceed by an initial 1, 4-addition which is followed by a 1, 2-silyl migration and a final cyclization step involving the derived boron enolate resulting in the construction of the cyclo-pentanoid product.

Lewis acid promoted asymmetric addition reactions of chiral (£)-crotylsilanes with acetals and aldehydes have been shown to proceed with high levels of diastereose-lection to form highly functionalized homoallylic ethers, 1 tetrahydrofurans, 2 and 7-alkoxy-a-amino acid synthons. 3 These asymmetric reaction processes are initiated by a simple bimolecular reaction which is consistent with an anti-Se'process. In studies designed to further probe the utility of the these organosilane reagents we have learned that they undergo asymmetric conjugate addition reactions with «-substituted «,/3-unsaturated enals and methyl vinyl ketone 2 resulting in the formation of tetrasubstituted