Organocatalytic Asymmetric Hetero-Diels–Alder Reaction of in Situ Generated Dienes: Access to α,β-Unsaturated δ‑Lactones Featuring CF₃‑Substituted Quaternary Stereocenter

Chiral bifunctional urea-catalyzed asymmetric direct hetero-Diels–Alder reaction between alkylidene azlactone-derived dienes and trifluoromethyl aryl ketones is reported for the first time. The direct hetero-Diels–Alder reaction followed by ring opening results in densely functionalized α,β-unsaturated δ-lactones featuring a CF₃-substituted quaternary stereocenter in high yields with excellent enantioselectivities. The method is compatible over a range of substrates. Moreover, the reaction is scaled up and the α,β-unsaturated δ-lactones were converted to amino acid derivatives decorated with trifluoromethylated carbinol functionality.