Mitra Mainak, Cusso Olaf, Bhat Satish S, Sun Mingzhe, Cianfanelli Marco, Costas Miquel, Nordlander Ebbe
Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden.
Dalton Trans. 2019 May 7;48(18):6123-6131. doi: 10.1039/c8dt04449j.
The chiral tetradentate N4-donor ligand, 1-methyl-2-({(S)-2-[(S)-1-(1-methylbenzimidazol-2-yl methyl)pyrrolidin-2-yl]pyrrolidin-1-yl}methyl) benzimidazole (S,S-PDBzL), based on a chiral dipyrrolidine backbone, has been synthesized and its corresponding Fe(ii) complex has been prepared and characterized. The X-ray structure of the complex reveals that the Fe(ii) ion is in a distorted octahedral coordination environment with two cis-oriented coordination sites occupied by (labile) triflate anions. The ability of the iron complex to catalyze asymmetric epoxidation reactions of olefins with H2O2 was investigated, using 2-cyclohexen-1-one, 2-cyclopenten-1-one, cis-β-methylstyrene, isophorone, chalcones and tetralones as substrates. Different carboxylic acids were used as additives to enhance yields and enantioselectivities, and 2-ethylhexanoic acid was found to give the best results. The catalysis results indicate that the Fe(ii) complex is capable of effecting comparatively high enantioselectivities (>80%) in the epoxidation reactions.
基于手性二吡咯烷骨架合成了手性四齿N4供体配体1-甲基-2-({(S)-2-[(S)-1-(1-甲基苯并咪唑-2-基甲基)吡咯烷-2-基]吡咯烷-1-基}甲基)苯并咪唑(S,S-PDBzL)，并制备和表征了其相应的Fe(ii)配合物。该配合物的X射线结构表明，Fe(ii)离子处于扭曲的八面体配位环境中，两个顺式配位位点被(不稳定的)三氟甲磺酸根阴离子占据。以2-环己烯-1-酮、2-环戊烯-1-酮、顺-β-甲基苯乙烯、异佛尔酮、查尔酮和四氢萘酮为底物，研究了铁配合物催化烯烃与H2O2不对称环氧化反应的能力。使用不同的羧酸作为添加剂以提高产率和对映选择性，发现2-乙基己酸给出了最佳结果。催化结果表明该Fe(ii)配合物在环氧化反应中能够实现较高的对映选择性(>80%)。
