The intramolecular Diels–Alder reaction of an ester-tethered 1,3,9-decatriene system was significantly accelerated in ionic liquids such as [emim]BF4, [bmim]BF4 and [bdmim]BF4. Under the present conditions, the IMDA reaction proceeded smoothly without the use of Lewis acid catalysts to give cis-fused bicyclic lactones in good yield with high diastereoselectivity.
