Allylsilanes by the regio- and stereocontrolled substitution of metalated homoallylsilanes

Metalation of Me3Si(CH2)2CH:CH2 (I) with BuLi/KOCMe3, followed by quenching with electrophiles, gave chain-lengthened Z-allylsilanes with high regio- and stereoselectivity, along with lesser amts. of homoallylsilanes. Thus, metalation of I, followed by treatment with BuI, gave 74% Z-Me3SiCH2CH:CHCH2Bu and Me3SiCH2CHBuCH:CH2 (83:17 ratio).