LAUSR

A very efficient and selective telomerization of 1,3‐butadiene with CO2 that leads to the δ‐lactone (3‐ethylidene‐6‐vinyltetrahydro‐2H‐pyran‐2‐one) was obtained using palladium acetate and tris(p‐methoxyphenyl)phosphine as a catalyst in the presence of p‐hydroquinone, N,N‐diisopropylethylamine, and acetonitrile. A high turnover number of 4500 with 96 % selectivity to the δ‐lactone was obtained after 5 h reaction at 70 °C. The reaction was deactivated by the presence of different 1,3‐dialkylimidazolium ionic liquids, possibly by the formation of stable and inactive palladium‐imidazole‐2‐ylidene carbenes.