Au(Ⅰ)-Catalyzed Enantioselective 1,3-Dipolar Cycloadditions of Muenchnones with Electron-Deficient Alkenes

摘要

Synthetic methods relying on gold complexes as catalysts have recently been the focus of intense development. Despite numerous advances, relatively few enantioselective gold-catalyzed transformations have been described. The earliest example of an enantioselective gold(Ⅰ)-catalyzed transformation, the Hayashi—Ito aldol reaction, was proposed to rely on activation of the nucleophile as a chiral monophosphineAu(Ⅰ) enolate. In contrast, the majority of recently reported methods rely on the electrophilic nature of cationic bisphosphinegold(Ⅰ) complexes to activate π-bonds toward addition of nucleophiles. Therefore, the utility of chiral bisphosphinegold-(Ⅰ) complexes would be signficantly extended if they could be employed as catalysts for enantioselective transformations that are not predicated on π-bond activation. To this end, herein we describe the development of a bisphosphinegold(Ⅰ)-catalyzed enantioselective 1,3-dipolar cycloaddition reaction of mesoionic azomethine ylides (muenchnones) with alkenes.