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 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.