Synlett, Inhaltsverzeichnis Synlett 2024; 35(09): 983-988DOI: 10.1055/s-0042-1751527 cluster Chemical Synthesis and Catalysis in Germany Remote Enantioselective Epoxidation Reactions Catalyzed by Chiral Iron Porphyrin Complexes with a Hydrogen-Bonding Site Hussayn Ahmed a Technische Universität München, School of Natural Sciences Department Chemie and Catalysis Research Center (CRC), 85747 Garching, Germany , Alexander Pöthig a Technische Universität München, School of Natural Sciences Department Chemie and Catalysis Research Center (CRC), 85747 Garching, Germany , Khai-Nghi Truong b Rigaku Europe SE, Hugenottenallee 167, 63263 Neu-Isenburg, Germany , Thorsten Bach ∗ a Technische Universität München, School of Natural Sciences Department Chemie and Catalysis Research Center (CRC), 85747 Garching, Germany › Institutsangaben Artikel empfehlen Abstract Artikel einzeln kaufen Alle Artikel dieser Rubrik Abstract Iron porphyrin complexes, which were linked via a para-phenylethynyl group to a chiral scaffold with a lactam binding site, were probed as catalysts in the enantioselective epoxidation of 4-(ω-alkenyl)-quinolones. It was found that the 3-butenyl group in the substrate accounts for the highest enantioselectivity (up to 44% ee) and the absolute configuration of an oxirane product was elucidated by electron diffraction. A two-point hydrogen bond of the substrate to the catalyst is likely responsible for enantioface differentiation at a remote position. The study shows chirality transfer to be possible via four nonstereogenic carbon atoms between the binding site of the substrate and its reactive C=C double bond. Key words Key wordscatalysis - enantioselectivity - epoxidation - iron - porphyrins Volltext Referenzen References and Notes 1a Katsuki T, Sharpless KB. J. Am. Chem. Soc. 1980; 102: 5974 1b Gao Y, Hanson RM, Klunder JM, Masamune H, Ko SY, Sharpless KB. J. Am. Chem. Soc. 1987; 109: 5765 1c Finn MG, Sharpless KB. J. Am. Chem. Soc. 1991; 113: 113 Reviews: 2a Reek JN. H, de Bruin B, Pullen S, Mooibroek TJ, Kluwer AM, Caumes X. Chem. 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Catal. 2023; 365: 1629 18 Xu D, Kaiser F, Li H, Reich RM, Guo H, Kühn FE. Org. Biomol. Chem. 2019; 17: 49 19 Representative Procedure for the Fe-Catalyzed Epoxidation The iron porphyrin catalyst (0.20 mol%) was dissolved in anhydrous CH2Cl2 (5 mL per 50 μmol substrate) and added to the substrate (1.00 equiv.) in a flame dried Schlenk tube. The solution was stirred for 10 min at 0 °C. PhIO (1.00 equiv.) was added to the reaction solution in one portion, and the resulting reaction suspension was stirred for 4 h at 0 °C. The reaction was stopped by removing the solvent in vacuo, and the crude material was purified by automated column chromatography (MeOH/CH2Cl2 0/100 → 3/97 or EtOAc/hexanes 5/95 → 75/25). Exemplarily, product 10b (3.3 mg, 15.3 μmol, 31%, 44% ee) was obtained from substrate 2b (10.0 mg, 0.05 mmol) and iron porphyrin 5 (114 μg, 0.10 μmol) after purification by automated column chromatography (MeOH/CH2Cl2 0/100 → 3/97) as an off-white solid. 1H NMR (500 MHz, DMSO-d 6, 298 K): δ = 11.65 (s, 1 H, NH), 7.77 (dd, 3 J = 8.2 Hz, 4 J = 1.2 Hz, 1 H, H-5), 7.49 (ddd, 3 J = 8.2 Hz, 3 J = 7.1 Hz, 4 J = 1.2 Hz, 1 H, H-7), 7.31 (dd, 3 J = 8.2 Hz, 4 J = 1.2 Hz, 1 H, H-8), 7.20 (ddd, 3 J = 8.2 Hz, 3 J = 7.1 Hz, 3 J = 1.2 Hz, 1 H, H-6), 6.39 (s, 1 H, H-3), 3.07–3.00 (m, 1 H, H-3′), 2.99–2.86 (m, 2 H, H-1′), 2.71 (dd, 2 J = 5.1 Hz, 3 J = 4.0 Hz, 1 H, H-4′), 2.53–2.51 (m, 1 H, H-4′), 1.94–1.83 (m, 1 H, H-2′), 1.82–1.71 (m, 1 H, H-2′) ppm. 13C NMR (126 MHz, DMSO-d 6, 298 K): δ = 162.1 (s, C=O), 151.3 (s, C-4), 139.4 (s, C-8a), 130.7 (d, C-7), 124.8 (d, C-5), 122.2 (d, C-6), 120.6 (d, C-3), 119.1 (s, C-7a), 116.2 (d, C-8), 51.6 (d, C-3′), 46.7 (t, C-4′), 31.8 (t, C-2′), 28.2 (t, C-1′). Chiral HPLC: 44% ee [©CHIRALPAK AD-H 250 × 4.6 mm, 20 °C, 10% i-PrOH/n-heptane, 1 mL/min, 210 nm, t R = 26.1 min (major), t R = 27.7 min (minor). 20 Ito S, White FJ, Okunishi E, Aoyama Y, Yamano A, Sato H, Ferrara JD, Jasnowski M, Meyer M. CrystEngComm 2021; 23: 8622 21a Truong K.-N, Ito S, Wojciechowski JM, Göb CR, Schürmann CJ, Yamano A, Del Campo M, Okunishi E, Aoyama Y, Mihira T, Hosogi N, Benet-Buchholz J, Escudero-Adán EC, White FJ, Ferrara JD, Bücker R. Symmetry 2023; 15: 1555 21b Klar PB, Krysiak Y, Xu H, Steciuk G, Cho J, Zou X, Palatinus L. Nat. Chem. 2023; 15: 848 Zusatzmaterial Zusatzmaterial Supporting Information