By combining an iron-catalyzed borrowing hydrogen of allylic alcohols with an enantioselective
organocatalyzed Michael addition of β-keto esters followed by a subsequent DBU-promoted
lactonization different enantioenriched δ-lactones have been synthesized with good
enantioselectivities. The valuable building blocks, featuring in some cases challenging
quaternary stereocenters, have been obtained with >90% ee.
Key words
organocatalysis - iron catalysis - lactone synthesis - borrowing hydrogen - multi-catalysis