When treated with 2 equiv of a BuLi/KOCMe3 mixt., terminal olefins carrying unprotected OH or CO2H groups generate allylmetal intermediates which are trapped with Me3SiCl to afford functionalized (Z-2-alkenyl)trimethylsilanes. E.g., treating CH2:CHMeCO2H with 2 equiv BuLi/KOCMe3 in THF followed by Me3SiCl gave 52% E-Me3SiCH2CH:CMeCO2H. One equivalent of the superbasic reagent suffices if the unsatd. alcs. are first protected as acetals before being subjected to the metalation/silylation/hydrolysis sequence. [on SciFinder (R)]