Asymmetric Construction of 3,4-Diamino Pyrrolidines via Chiral <i>N,O</i>-Ligand/Cu(I) Catalyzed 1,3-Dipolar Cycloaddition of Azomethine Ylides with β‑Phthalimido­nitroethene

A series of chiral N,O-ligands derived from a 1,2-dihydro­imidazo­[1,2-a]­quinolone motif have been evaluated for the asymmetric 1,3-dipolar cycloaddition of azomethine ylides with a novel dipolarophile β-phthalimido­nitroethene. A newly designed DHIPOH ligand 7c bearing 1-methyl and 4-iodo substituents was found to have significant “synergistic steric effects” and consequently afforded the corresponding 4-nitro-3-amino­pyrrolidines with excellent diastereo- (dr up to 98:2) and enantio selectivities (ee up to 99%). Subsequent Raney Ni-catalyzed reduction and deprotection of phthalyl led to the structurally and biologically important 3,4-diamino­pyrrolidines in a straightforward and efficient pathway.一系列基于1,2-二氢咪唑并[1,2-a]喹啉酮（1,2-dihydroimidazo[1,2-a]quinolone）母核的手性N,O-配体，已被用于评估甲亚胺叶立德与新型亲偶极体β-邻苯二甲酰亚氨基硝基乙烯的不对称1,3-偶极环加成反应性能。研究发现，一款经全新设计、带有1-甲基和4-碘取代基的DHIPOH配体7c，展现出显著的"协同空间位阻效应"，可得到对应的4-硝基-3-氨基吡咯烷产物，其非对映选择性（dr最高可达98:2）与对映选择性（ee最高可达99%）均十分优异。后续通过雷尼镍（Raney Ni）催化还原与邻苯二甲酰基脱保护步骤，以简洁高效的合成路径得到了具有重要结构与生物学意义的3,4-二氨基吡咯烷。