The palladium (II) catalyzed direct C3-(sp2)-H alkenylation of five membered heterocyclic aldehydes has been developed using 3-aminobutanoic acid as a catalytic transient directing group. A wide range of heterocyclic aldehydes reacted with various acrylates to afford highly site-selective C3-alkenylated products. This method features an exclusive E-selective alkenylation at the C3-position of heterocyclic aldehydes with a broad substrate scope. The protocol also proved to be useful to construct the mechanochromic luminogen.