Selective palladium-catalysed synthesis of diesters: Alkoxycarbonylation of a CO₂-butadiene derived δ-lactone

Novel unsaturated C₁₀ diesters are produced via the alkoxycarbonylation of δ-lactone 1 (3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one), derived from the telomerization of CO₂ and butadiene. The key for the selective valorization of 1 is the use of a catalytic system based on PdCl₂, a chelating phosphine bearing electron-withdrawing groups and an acidic promoter. The unsaturated C₁₀ methyl diester can be easily hydrogenated on Pd/C under mild conditions to afford its corresponding saturated diester. Subsequent hydrogenation using the homogeneous [Ru(acac)₃]/Triphos catalysts gives 2-ethyloctane-1,8-diol in high yield. The overall procedure allows synthesizing new building blocks for the manufacturing of renewable polymers and polymer processing materials.