42070-92-8Relevant articles and documents
Synthesis, coordination behavior, and structural features of chiral amino-, pyrazolyl-, and phosphino-substituted ferrocenyloxazolines and their application in asymmetric hydrogenations
Schuecker, Raffael,Zirakzadeh, Afrooz,Mereiter, Kurt,Spindler, Felix,Weissensteiner, Walter
, p. 4711 - 4719 (2011)
A highly flexible and modular synthesis of 15 chiral nonracemic ferrocenyloxazolines-all based on a ferrocenylethyl backbone-is described. Starting from N,N-dimethylaminoethyl ferrocene a range of oxazoline derivatives with various oxazoline substituents were prepared in a three-step sequence. After reaction with methyl iodide, the quaternized dimethylamino group was replaced by different amino, pyrazolyl, and phosphinyl groups. Subsequent reduction of the phosphinyl groups gave phosphinooxazoline derivatives. The molecular structures of three palladium [PdCl2(L)] and three ruthenium [RuCl(p-cymene)(L)]PF6 complexes of representative ferrocenyloxazoline ligands were studied by X-ray diffraction. In addition, five ruthenium complexes [RuCl2(PPh3)(L)] were prepared. These complexes were tested, using a high-throughput screening system, in the asymmetric hydrogenation of three ketones. Enantioselectivities of up to 99% ee were obtained.
Cinchona-Alkaloid-Derived NNP Ligand for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones
Zhang, Lin,Zhang, Ling,Chen, Qian,Li, Linlin,Jiang, Jian,Sun, Hao,Zhao, Chong,Yang, Yuanyong,Li, Chun
supporting information, p. 415 - 419 (2022/01/12)
Most ligands applied for asymmetric hydrogenation are synthesized via multistep reactions with expensive chemical reagents. Herein, a series of novel and easily accessed cinchona-alkaloid-based NNP ligands have been developed in two steps. By combining [Ir(COD)Cl]2, 39 ketones including aromatic, heteroaryl, and alkyl ketones have been hydrogenated, all affording valuable chiral alcohols with 96.0-99.9% ee. A plausible reaction mechanism was discussed by NMR, HRMS, and DFT, and an activating model involving trihydride was verified.
Synthesis, characterization and catalytic performance in enantioselective reactions by mesoporous silica materials functionalized with chiral thiourea-amine ligand
G?k, Ya?ar,G?k, Halil Zeki
, p. 853 - 874 (2020/11/10)
Chiral heterogeneous catalysts have been synthesized by grafting of silyl derivatives of (1R, 2R)- or (1S, 2S)-1,2-diphenylethane-1,2-diamine on SBA-15 mesoporous support. The mesoporous material SBA-15 and so-prepared chiral heterogeneous catalysts were characterized by a combination of different techniques such as X-ray diffractometry (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) surface area. Results showed that (1R, 2R)- and (1S, 2S)-1,2-diphenylethane-1,2-diamine were successively immobilized on SBA-15 mesoporous support. Chiral heterogeneous catalysts and their homogenous counterparts were tested in enantioselective transfer hydrogenation of aromatic ketones and enantioselective Michael addition of acetylacetone to β-nitroolefin derivatives. The catalysts demonstrated notably high catalytic conversions (up to 99%) with moderate enantiomeric excess (up to 30% ee) for the heterogeneous enantioselective transfer hydrogenation. The catalytic performances for enantioselective Michael reaction showed excellent activities (up to 99%) with poor enantioselectivities. Particularly, the chiral heterogeneous catalysts could be readily recycled for Michael reaction and reused in three consecutive catalytic experiments with no loss of catalytic efficacies.
Exploration of highly electron-rich manganese complexes in enantioselective oxidation catalysis; A focus on enantioselective benzylic oxidation
Klein Gebbink, Robertus J. M.,Li, Fanshi,Lutz, Martin,Masferrer-Rius, Eduard
, p. 7751 - 7763 (2021/12/13)
The direct enantioselective hydroxylation of benzylic C-H bonds to form chiral benzylic alcohols represents a challenging transformation. Herein, we report on the exploration of new biologically inspired manganese and iron complexes bearing highly electron-rich aminopyridine ligands containing 4-pyrrolidinopyridine moieties ((S,S)-1, (R,R)-1, 2 and 5) in combination with chiral bis-pyrrolidine and N,N-cyclohexanediamine backbones in enantioselective oxidation catalysis with aqueous H2O2. The current manganese complexes outperform the analogous manganese complexes containing 4-dimethylaminopyridine moieties (3 and 4) in benzylic oxidation reactions in terms of alcohol yield while keeping similar ee values (～60% ee), which is attributed to the higher basicity of the 4-pyrrolidinopyridine group. A detailed investigation of different carboxylic acid additives in enantioselective benzylic oxidation provides new insights into how to rationally enhance enantioselectivities by means of proper tuning of the environment around the catalytic active site, and has resulted in the selection of Boc-l-Tert-leucine as the preferred additive. Using these optimized conditions, manganese complex 2 was shown to be effective in the enantioselective benzylic oxidation of a series of arylalkane substrates with up to 50% alcohol yield and 62% product ee. A final set of experiments also highlights the use of the new 4-pyrrolidinopyridine-based complexes in the asymmetric epoxidation of olefins (up to 98% epoxide yield and >99% ee).
