Catalytic Enantioselective Friedel−Crafts/Michael Addition Reactions of Indoles to Ethenetricarboxylates

The Friedel−Crafts reaction is an important reaction for the formation of new C−C bonds. Recently,
catalytic enantioselective Friedel−Crafts reaction of alkylidene malonates has been reported. However,
the substituents in alkylidene malonates are limited. To explore new substituents such as carboxyl and
carbonyl groups, catalytic enantioselective Friedel−Crafts reactions of reactive ethenetricarboxylates and
acyl-substituted methylenemalonates 1 were investigated. The reaction of 1 with indoles in the presence
of catalytic amounts of chiral bisoxazoline copper(II) complex (10%) in THF at room temperature gave
alkylated products in high yields and up to 95% ee. The enantioselectivity can be explained by the
secondary orbital interaction on approach of indole to the less hindered side of the 1−Cu(II)−ligand
complex.