Telomerization of 1,3‐Butadiene with Carbon Dioxide: A Highly Efficient Process for δ‐Lactone Generation

Abstract A very efficient and selective telomerization of 1,3‐butadiene with CO 2 that leads to the δ‐lactone (3‐ethylidene‐6‐vinyltetrahydro‐2 H ‐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.