Gold(III) Chloride-Catalyzed Diastereoselective Alkylation Reactions with Chiral Benzylic Acetates

摘要

Gold(III) chloride was shown to be an efficient catalyst for the diastereoselective C-C bond formation of various chiral para-methoxybenzylic acetates and different nucleophiles.All electrophilic acetates carried next to the reacting center a stereo-genic carbon center bound to a functional group (FG),a methyl substituent and a proton.Selectivities were good (dr> 80/20) in favor of the anti-product for FG = COOMe,NO2,CN and in favor of the syn-product for FG = SO2Et,PO(OEt)2.The reactions proceed most likely via a free carbocation,in which a face differentation is facilitated by a preferred con-formation.Several arene nucleophiles were shown to be compatible with the catalysis conditions providing the corresponding substitution products in high yields (13 examples,62-98%).Moreover,other nucleophiles (allyltrimethylsilane,trimethylsilyl cyanide,2,2-dimethyl-3-(trimethylsilyloxy)butane,p-tol-uenesulfonamide,and acetylacetone) reacted with a representative chiral electrophile in a high yielding and diastereoselective fashion.