Tandem reaction: The Pd‐catalyzed three‐component coupling reaction of an allylic alcohol, terminal alkyne, and organoborane to give (E)‐1‐substituted 2‐alkyl‐1,4‐pentadienes, involving geminal allylation and alkylation at the acetylenic terminal carbon, is described. Bis‐diene undergoes a similar multicomponent coupling reaction with acetylene and organoborane, involving cyclization of bis‐π‐allylpalladium