Chiral Ph-dbfox (Ph-dbfox = (R,R)-4,6-dibenzofurandiyl-2,2′-bis(4-phenyloxazoline))/Zn(NTf2)2catalyzed enantioselective Friedel–Crafts reactions of β-CF3acrylates with pyrroles and indoles have been investigated, which afforded the corresponding chiral trifluoromethyl pyrrole and indole derivatives in high yields (90–99%) with a range of 66–99% ee values. With the aid of the chiral adduct of the asymmetric Friedel–Crafts reaction, the chiral trifluoromethylated heliotridane has been successfully constructed in good total yield. [ABSTRACT FROM AUTHOR]
CHIRALITY, ASYMMETRY (Chemistry), CHEMICAL reactions, CHEMICAL processes, CHEMICAL reagents, INTERMEDIATES (Chemistry), STEREOSELECTIVE reactions
Abstract
Chemical reactions and processes often involve cationic reagents, intermediates or products in prochiral or chiral racemic form. To afford instead non-racemic compounds, an asymmetric ion pairing of the cations with chiral anionic counterions can be considered. This review presents recent examples of the synthesis and use of chiral anions for such stereoselective purposes. [ABSTRACT FROM AUTHOR]