Metal-Free Synthesis of Conjugated Dienyl Esters via Coupling of Halopenta-1,4-dienes with Carboxylic Acids

This study presents a novel, metal-free method for synthesizing conjugated dienyl esters through the base-catalyzed remote migratory nucleophilic substitution reaction of halopenta-1,4-diene derivatives. Experimental and density functional theory (DFT) calculations confirm that bromine not only acts as a leaving group but also modulates electronic distribution within the molecule. This facilitates a remote migratory process to form 5-bromopenta-1,3-diene from 1-bromopenta-1,4-diene, followed by nucleophilic addition with a carboxylate anion with a lower energy barrier of 25.9 kcal/mol, yielding a thermodynamically stable product.