Organocatalytic Asymmetric Approach to γ,δ-Functionalization of 3-Cyano-4-styrylcoumarins via Bifunctional Catalysis.

A novel organocatalytic reaction cascade between 3-cyano-4-styrylcoumarins and 2-mercaptoacetophenones is described. It is based on stereocontrolled functionalization of cyanocoumarins proceeding in a sequence of thia-Michael/aldol/annulation reactions. This highly diastereo- and enantioselective reaction is realized by employing enantioselective bifunctional catalysis and exhibits a broad substrate scope and excellent functional group tolerance. The synthetic application involves the transformation of the imidoester group, thus opening access to biologically relevant coumarin and δ-lactone-fused products.

Asymmetric Synthesis of [2.2.2]-Bicyclic Lactones via All-Carbon Inverse-Electron-Demand Diels-Alder Reaction.

In this paper, a new cycloaddition between α,ß-unsaturated aldehydes and coumalates realized under dienamine activation has been described. The reaction proceeds regioselectively with the distal double bond of the dienamine system acting as electron-rich dienophile. It leads to the formation of biologically relevant [2.2.2]-bicyclic lactones. Their functionalization potential has been confirmed in selected, diastereoselective transformations.