In the presence of boron trihalides, aryl aldehydes couple readily with allylmetals to afford haloallylated products. The reactions tolerate a variety of functional groups. Simple aqueous workup of haloallylation reactions, followed by treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene, provides a straightforward route to synthetically useful (E)-1,3-dienes. The mild reaction conditions, readily available