73890-73-0Relevant academic research and scientific papers
Rhizopus arrhizus mediated SAR studies in chemoselective biotransformation of haloketones at ambient temperature
Salokhe, Prabha R.,Salunkhe, Rajeshri S.
, (2021/09/13)
We have demonstrated a green chemistry approach using the fungus Rhizopus arrhizus for the reductive dehalogenation and synthesis of chiral secondary carbinols and halohydrins of pharmaceutical importance in mild, inexpensive, and environmental friendly process at ambient temperature. In the present study, we have succeeded in unravelling the relationship between the position of the substituent group in the structure of substrate and bioreduction activity of the fungus Rhizopus arrhizus. The asymmetric reduction of the carbonyl group to corresponding chiral halohydrin takes place with good yield and excellent enantiomeric excess (≥92%) when the substituent halogen is on the aromatic nucleus. However, novel results concerning reductive dehalogenation are obtained when halogen is incorporated in the alkyl side chain. Thus, the fungus Rhizopus arrhizus has great potential to bring chemoenzymatic biotransformation of halo ketones. Various influential processing parameters such as microbe selection, temperature, pH, etc. were also investigated to optimize the growth of biocatalyst.
Towards practical earth abundant reduction catalysis: Design of improved catalysts for manganese catalysed hydrogenation
Widegren, Magnus B.,Clarke, Matthew L.
, p. 6047 - 6058 (2019/11/14)
Manganese catalysts derived from tridentate P,N,N ligands can be activated easily using weak bases for both ketone and ester hydrogenations. Kinetic studies indicate the ketone hydrogenations are 0th order in acetophenone, positive order in hydrogen and 1st order in the catalyst. This implies that the rate determining step of the reaction was the activation of hydrogen. New ligand systems with varying donor strength were studied and it was possible to make the hydrogen activation significantly more efficient; a catalyst displaying around a 3-fold increase in initial turn-over frequencies for the hydrogenation of acetophenone relative to the parent system was discovered as a result of these kinetic investigations. Ester hydrogenations and ketone transfer hydrogenation (isopropanol as reductant) are first order for both the substrate and catalysts. Kinetic studies also gained insight into catalyst stability and identified a working range in which the catalyst is stable throughout the catalytic reaction (and a larger working range where high yields can still be achieved). The new more active catalyst, combining an electron-rich phosphine with an electron-rich pyridine is capable of hydrogenating acetophenone using as little as 0.01 mol% catalyst at 65 °C. In all, protocols for reduction of 21 ketones and 15 esters are described.
Chirality-Economy Catalysis: Asymmetric Transfer Hydrogenation of Ketones by Ru-Catalysts of Minimal Stereogenicity
Chen, Fumin,He, Dongxu,Chen, Li,Chang, Xiaoyong,Wang, David Zhigang,Xu, Chen,Xing, Xiangyou
, p. 5562 - 5566 (2019/06/05)
This manuscript describes the design and synthesis of Ru catalysts that feature only a single stereogenic element, yet this minimal chirality resource is demonstrated to be competent for effecting high levels of stereoinduction in the asymmetric transfer hydrogenation over a broad range of ketone substrates, including those that are not accommodated by known catalyst systems. The single stereogenic center of the (1-pyridine-2-yl)methanamine) is the only point-chirality in the catalysts, which simplifies this catalyst system relative to existing literature protocols.
Central-to-Helical-to-Axial-to-Central Transfer of Chirality with a Photoresponsive Catalyst
Pizzolato, Stefano F.,?tacko, Peter,Kistemaker, Jos C. M.,Van Leeuwen, Thomas,Otten, Edwin,Feringa, Ben L.
supporting information, p. 17278 - 17289 (2019/01/04)
Recent advances in molecular design have displayed striking examples of dynamic chirality transfer between various elements of chirality, e.g., from central to either helical or axial chirality and vice versa. While considerable progress in atroposelective synthesis has been made, it is intriguing to design chiral molecular switches able to provide selective and dynamic control of axial chirality with an external stimulus to modulate stereochemical functions. Here, we report the synthesis and characterization of a photoresponsive bis(2-phenol)-substituted molecular switch 1. The unique design exhibits a dynamic hybrid central-helical-axial transfer of chirality. The change of preferential axial chirality in the biaryl motif is coupled to the reversible switching of helicity of the overcrowded alkene core, dictated by the fixed stereogenic center. The potential for dynamic control of axial chirality was demonstrated by using (R)-1 as switchable catalyst to direct the stereochemical outcome of the catalytic enantioselective addition of diethylzinc to aromatic aldehydes, with successful reversal of enantioselectivity for several substrates.
Axially chiral tridentate isoquinoline derived ligands for diethylzinc addition to aldehydes
Sweetman, Brian A.,Guiry, Patrick J.
, p. 5567 - 5581 (2018/08/09)
The synthesis and resolution of new tridentate isoquinoline-derived ligands has been developed. The key steps in the synthetic sequence include successive, chemo-selective Suzuki-Miyaura cross-couplings of 1,3-dichloroisoquinoline with suitable arylboronic acids. The new ligands prepared in this manner were resolved either via molecular complexation with N-benzylcinchonidinium chloride as with 1-[3-(2-hydroxyphenyl)isoquinolin-1-yl]naphthalen-2-ol or via chromatographic separation of its epimeric camphorsulfonates as for 1,3-bis-(2-hydroxynaphthalen-1-yl)isoquinoline. 4-tert-Butyl-2-chloro-6-[1-(2-hydroxymethylnaphthalen-1-yl)isoquinolin-3-yl]phenol was resolved by chiral semi-preparative HPLC. The application of these ligands in the diethylzinc addition to aldehydes was investigated. In certain cases, the desired secondary alcohols were obtained in high yield with excellent enantiomeric excess (ee > 99%) at low catalyst loading (1 mol%).
Preparation of several BINOL-based polymeric ligands for the enantioselective addition of triethylaluminium to aromatic aldehydes
Liu, Dacai,Ouyang, Kunbing,Yang, Nianfa
, p. 1018 - 1023 (2016/01/30)
The synthesis of several polystyrene-supported BINOL (1,1-binaphthol) ligands via radical polymerization is described. These BINOL-based polymeric ligands were applied to the enantioselective addition of triethylaluminium to aromatic aldehyde in the presence of titanium isopropoxide. The products were obtained with up to 93% enantiomeric excess (ee) in good to excellent yield. The ligands were easily recovered and reused without losing their catalytic activity as well as enantioselectivity.
Development of Axially Chiral Cyclo-Biaryldiol Ligands with Adjustable Dihedral Angles
Zhang, Pengxiang,Yu, Jipan,Peng, Fei,Wu, Xudong,Jie, Jiyang,Liu, Can,Tian, Hua,Yang, Haijun,Fu, Hua
supporting information, p. 17477 - 17484 (2016/11/23)
A new type of axially chiral cyclo-[1,1′-biphenyl]-2,2′-diol (CYCNOL) ligands with adjustable dihedral angles have been developed by varying the bridge chain length. Eight-, nine- and ten-membered cyclo-ligands were prepared and evaluated by using two representative examples: enantioselective additions of diethylzinc to aldehydes and organometallic reagents to enones. The results revealed that the fine regulation of dihedral angles through variation of the bridge chain length was effective in the asymmetric synthesis.
Homochiral 2D Porous Covalent Organic Frameworks for Heterogeneous Asymmetric Catalysis
Wang, Xiuren,Han, Xing,Zhang, Jie,Wu, Xiaowei,Liu, Yan,Cui, Yong
supporting information, p. 12332 - 12335 (2016/10/07)
There have been breakthroughs in the development of covalent organic frameworks (COFs) with tunability of composition, structure, and function, but the synthesis of chiral COFs remains a great challenge. Here we report the construction of two-dimensional
Synthesis of dendrimer-supported ferrocenylmethyl aziridino alcohol ligands and their application in asymmetric catalysis
Zhao, Wen-Xian,Liu, Nian,Li, Gao-Wei,Chen, Dong-Li,Zhang, An-An,Wang, Min-Can,Liu, Lantao
supporting information, p. 2924 - 2930 (2015/05/27)
A series of N-ferrocenylmethyl aziridino alcohol ligands bearing Frchet-type dendrimers were synthesized and applied in the asymmetric addition of diethylzinc to aldehydes affording chiral alcohols in excellent yields (up to 99%) and excellent enantiosele
Enantioselective addition of diethylzinc to aldehydes catalyzed by aziridine carbinols
Wang, Xiaojuan,Zhao, Wenxian,Li, Gaowei,Liu, Guanjun,Wang, Jin,Wang, Mincan,Liu, Lantao
, p. 815 - 820 (2015/08/18)
Abstract A series of enantiopure aziridine carbinols were synthesized from commercially available starting materials (l-serine and piperonylaldehyde), and characterized by 1H NMR, 13C NMR, HRMS, and IR. Their enantioselective induction behaviors were evaluated as chiral ligands in the asymmetric addition of diethylzinc and phenylethynylzinc to aryl and α,β-unsaturated aldehydes. Chiral aziridine carbinol 1h was found to catalyze the asymmetric addition of diethylzinc to aldehydes at low catalyst loadings (as little as 1 mol %), and the conversion rates were close to quantitative (up to 97% yield) with good to excellent enantiomeric excesses (up to 98% ee). A possible catalytic reaction mechanism is proposed.
