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The allylboration of alkenes with allyldibromoborane is described. Utilizin
g an improved methodology for the synthesis of allyldibromoborane, 1,3-dien
es, styrene, and even isolated alkenes could be carbometalated in high yiel
d regio- and stereospecifically at 0 degrees C. This high reactivity of all
yldibromoborane significantly expands the scope of carbometalations of alke
nes.