Asymmetric Gold-Catalyzed Hydroarylation/Cyclization Reactions

The asymmetric gold-catalyzed hydroarylation/cyclization reactions of 1,6-enynes under mild conditions was investigated. A mixture of L-(AuCl) 2 (L=(R)-MeO-BIPHEP or (R)-4-MeO-3,5-(tBu)2MeOBIPHEP) (3 mol %) and AgOTf (6 mol %) in distilled Et2O was stirred under argon atmosphere at room temperature for 30 minutes. The aromatic nucleophile was then added and the mixture was stirred for 5 minutes. Enyne was finally added and the mixture was stirred until completion of the reaction. The mixture was then filtered through a short pad of silica to eliminate the catalyst and the solvents were evaporated under reduced pressure. the crude product was purified by silica gel flash chromatography. It was observed that the combination of atropisomeric electron-rich and hindered chiral ligand 4-MeO-3,5-(tBu) 2MeOBIPHEP associated to Au1 and silver salt promotes the enantioselective hydroarylation/cyclization reaction of 1,6-enynes.