Scalable Palladium-Catalyzed Alkoxycarbonylation of Conjugated Dienes

The Pd(cod)Cl₂-catalyzed alkoxycarbonylation of conjugated dienes to β,γ-unsaturated esters was approached by both intramolecular phosphinesulfonate L¹ and intermolecular PPh₃/PTSA in this study. However, the poor solubility of the Pd/L¹ complex and the labile monodentate Pd/PPh₃ structure restricts the system efficiency, especially for the scale-up application. By contrast, the stable and well-soluble bidentate Xantphos system allows for the quantitative formation of 3-pentenoate (96%) on a gram scale within 6 h in weakly alkaline N-methylpyrrolidone (NMP), which also functions as a basic site to promote the rate-limiting alcoholysis step while reducing the dosage of ligand to a theoretical value.