Catalytic Enantioselective Friedel−Crafts/Michael Addition Reactions of Indoles to Ethenetricarboxylates
                                
                                    
                                        作者:Shoko Yamazaki、Yuko Iwata                                    
                                    
                                        DOI:10.1021/jo052041p
                                    
                                    
                                        日期:2006.1.1
                                    
                                    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 methylenernalonates I 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.