Regiodivergent Vinylogous-Cyclization Reactions of Cyclic α-Amide Enone Acceptors: Synthesis of Highly Enantioenriched Heterobicyclic Structures.

Abstract

A vinylogous addition-cyclization reaction of cyclic α-amide enones with good yields and excellent regioselectivity catalyzed by cinchona squaramides has been reported. Using 4-aryl-3-butenyl N-acylpyrazoles as nucleophiles led to 1,4-selective γ-addition of enones, and 1,2-selective γ-addition of enones took place when 3-aryl-3-butenyl N-acylpyrazoles was used as the donors. The 1,4- and 1,2-selective γ-adducts are then formed into the corresponding highly stereoselective and enantioselective fused bicyclic and spirocyclic products by intramolecular cyclization. The synthetic utility of the products has also been demonstrated through further transformations of the products.