1-Alkenyl chlorides, bromides or iodides can be obtained with very high cis selectivities through Wittig reaction employing α-chloro, α-bromo α-iodo ylids derivefrom tris(2-methoxymethoxyphenyl)phospine. The corresponding α-methoxy substituted ylid produces enethers with again remarkably high cis/trans ratios. Palladium(II) catalyzed coupling of (Z)-1-iodo-1-heptene with ethyl acrylate affords ethyl