Transient Directing Group Enabled C3‐(sp2)−H Alkenylation of Five Membered Heterocyclic Aldehydes: An Access to Mechanochromic Luminogen

Abstract The palladium (II) catalyzed direct C3‐( sp 2 )−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.