A coupling reaction of electron‐deficient alkenyl ethers with silyl enolates catalyzed by InBr3 was achieved. Various silyl enolates and 2‐carbonylalkenyl ethers were applicable, giving the corresponding 1,5‐dioxo‐alk‐2‐enes with perfect stereoselectivity of the alkene moieties. The present coupling reaction proceeds via the 1,4‐addition of silyl enolates to alkenyl ethers followed by elimination of silyl alkoxides, in which moderate‐Lewis acidic InBr3 performs both the activation of alkenyl ethers and the elimination of alkoxy groups regardless of the presence of various coordinative functional groups.