Highly Enantioselective 1,3-dipolar Cycloaddition Of Azomethine Ylides Catalyzed By Copper(Ⅰ)/tf-biphamphos Complexes

摘要

Five-membered nitrogen heterocycles, especially the highly substituted pyrrolidines are very important pharmaceuticals, natural alkaloids, and building blocks in organic synthesis. The catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides to electron-deficient alkenes is one of the most powerful and diversity-oriented synthesis (DOS) for the construction of this type of structures. Since the first catalytic asymmetric 1,3-dipolar cycloaddition reported by Zhang employing the AgOAc/xylyl-FAP system, much attention has been paid to developing enantioselective protocols for the reaction over the past decade. Asymmetric 1,3-dipolar cycloadditions have been reported using chiral metal complexes such as Ag~Ⅰ, Zn~Ⅱ, Cu~(Ⅰ/Ⅱ), Ni~Ⅱ, Ca~Ⅱ, and organo-catalysts to afford moderate to high enantio-/diastereoslectivities. Most recently, Carretero and co-workers reported an efficient Cu~Ⅰ/ Fesulphos catalyzed 1,3-dipolar cycloadditions of azomethine ylides derived from glycinate, and excellent enantio-/diastereoslectivities were obtained especially when N-phenyl or methylmaleimide was used as a dipolarophile. For azomethine ylides derived from amino esters other than glycinate, however, such high efficiency and excellent enantio-/ diastereoslectivity have not been achieved so far. Therefore, there is substantial room for improvement in terms of efficiency and substrate scopes for 1,3-dipolar cycloadditions.