Highly enantioselective epoxidation of olefins by H2O2 catalyzed by a non-heme Fe(ii) catalyst of a chiral tetradentate ligand. Issue 18 (5th April 2019)

• Record Type: Journal Article
• Authors: Mitra, Mainak; Cusso, Olaf; Bhat, Satish S.; Sun, Mingzhe; Cianfanelli, Marco; Costas, Miquel; Nordlander, Ebbe
• Is Part Of: Dalton transactions. Volume 48:Issue 18(2019)
• Page Start: 6123
• Page End: 6131
• Publication Date: 2019-04-05
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c8dt04449j
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A new chiral Fe(ii )-complex mediates the asymmetric epoxidation of prochiral olefins with good enantioselectivity. Abstract : 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 - PDBz L), 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 H2 O2 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.