120466-74-2Relevant academic research and scientific papers
Synthesis and evaluation of hemisalen type ligands based on chiral diamine and their use with ruthenium (II) as water-soluble catalysts for the ATH of aromatic ketones
Boukachabia, Mourad,Aribi-Zouioueche, Louisa,Riant, Olivier
, p. 95 - 101 (2018)
We have developed a robust ruthenium (II) complex catalyst coordinated by chiral Schiff bases for the reduction of acetophenone by ATH in water. The results show a significant effect of the nature of the chiral entity on the reactivity and the selectivity of the catalytic system. The Schiff base synthesized from the chiral diamine is more reactive and selective than the Schiff base synthesized from chiral amino alcohol. The reduction of acetophenone by catalysts coordinated with hemisalen ligands synthesized from chiral cyclohexyl diamine (1–4) gives high asymmetric inductions with ee up to 84% and total conversion. The effectiveness of the best ligand has been evaluating on a set of aromatic/heterocyclic ketones and was resulted to the corresponding alcohols with high enantioselectivities and good yields. A multigram-scale of the reduction process was applied on chroman-4-one and giving access to (R)-(+)-chromanol-4-ol with 87% ee and yield of 79%.
Preparation of homochiral chroman-4-ols and thiochroman-4-ols by microbial biotransformation
Holland,Manoharan,Schweizer
, p. 335 - 338 (1991)
Reduction of the carbonyl groups of chromanone and thiochromanone by Mortierella isabellina ATCC 42613 proceeds to give the (S) alcohols in high yield and enantiomeric excess. Benzylic hydroxylation of chroman by this fungus provides (R)-chroman-4-ol, and the (R) enantiomer of thiochroman-4-ol is obtained by bioconversion of thiochromanone or (±)-thiochroman-4-ol by Helminthosporium species NRRL 4671.
Asymmetric hydrogenation of aromatic heterocyclic ketones catalyzed by the MsDPEN-Cp*Ir(III) complex
Utsumi, Noriyuki,Tsutsumi, Kunihiko,Watanabe, Masahiko,Murata, Kunihiko,Arai, Noriyoshi,Kurono, Nobuhito,Ohkuma, Takeshi
, p. 141 - 147 (2010)
Asymmetric hydrogenation of aromatic heterocyclic ketones catalyzed by Cp*Ir(OTf)(Msdpen) (MsDPEN = N-(methanesulfonyl)-l,2-diphenylethylenediamine) affords the heterocyclic alcohols in 93% to >99% ee. The reaction is conducted in a methanolic solution with a substrate-to-catalyst molar ratio of 200-5000 under 15 atm of H2. The heterocyclic rings of substrates are left intact.
Polystyrene-supported triphenylsilyl chloride for the silylation-based kinetic resolution of secondary alcohols
Akhani, Ravish K.,Clark, Robert W.,Yuan, Liang,Wang, Li,Tang, Chuanbing,Wiskur, Sheryl L.
, p. 1527 - 1530 (2015)
A silyl chloride derivatized styrene polymer was employed in the silylation-based kinetic resolution of secondary alcohols for chromatography-free separation of alcohol enantiomers. Synthetically useful selectivity factors were obtained; furthermore, the polymer was recycled for use in a subsequent kinetic resolution, and it maintained its selectivity and integrity. Probability of precipitation: A silyl chloride polymer is employed in a kinetic resolution for the chromatography-free separation of enantiomers. After one enantiomer is covalently bonded to the polymer, it is precipitated from the solution for easy recovery. The polymer can also be recycled in subsequent kinetic resolutions without loss in selectivity.
Practical access to (S)-heterocyclic aromatic acetates via CAL-B/Na2CO3-deacylation and Mitsunobu reaction protocol
Aribi-Zouioueche, Louisa,Bra?a, Nabila,Merabet-Khelassi, Mounia,Toffano, Martial
, (2022/02/11)
Herein, we report the preparation of enantiomerically pure forms of 2,3-dihydrobenzofuran-3-ol (1), chroman-4-ol (2), thiochroman-4-ol (3), 1-(furan-2-yl) ethanol (5) and 1-(thiophen-2-yl) ethanol (6), through a kinetic resolution catalysed by Candida antarctica lipase B/Na2CO3 hydrolysis sequence in organic media. The (R)-furnished alcohols and the (S)-remained acetates are recovered enantiopures (ee?>99%, E???200, Conv = 50%). Those ideal enzymatic kinetic resolution (EKRs) are well incorporated to the Mitsunobu inversion protocol in a one pot procedure to give (S)-heterocyclic acetates (1a–3a) in good to high enantiomeric excess (88%–92% ee). Whilst, the (S)-heteroaromatic acetates (5a and 6a) are given with moderate enantiomeric excess (51%–62% ee). All the (S)-acetates are given in good isolated chemical yields (>80%) allowing to overcome the maximum of 50% yield which could be usually reached in a regular kinetic resolution processes.
Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
Oestreich, Martin,Seliger, Jan
, p. 247 - 251 (2020/10/29)
A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often-used ruthenium half-sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.
Chitosan as a chiral ligand and organocatalyst: Preparation conditions-property-catalytic performance relationships
Kolcsár, Vanessza Judit,Sz?ll?si, Gy?rgy
, p. 7652 - 7666 (2021/12/13)
Chitosan is an abundant and renewable chirality source of natural origin. The effect of the preparation conditions by alkaline hydrolysis of chitin on the properties of chitosan was studied. The materials obtained were used as ligands in the ruthenium-catalysed asymmetric transfer hydrogenation of aromatic prochiral ketones and oxidative kinetic resolution of benzylic alcohols as well as organocatalysts in the Michael addition of isobutyraldehyde to N-substituted maleimides. The degrees of deacetylation of the prepared materials were determined by 1H NMR, FT-IR and UV-vis spectroscopy, the molecular weights by viscosity measurements, their crystallinity by WAXRD, and their morphology by SEM and TEM investigations. The materials were also characterized by Raman spectroscopy. The biopolymers which have molecular weights in a narrow (200-230 kDa) range and appropriate (80-95%) degrees of deacetylation were the most efficient ligands in the enantioselective transfer hydrogenation, whereas in the oxidative kinetic resolution the activity of the complexes and the stereoselectivity increased with the degree of deacetylation. The chirality of the chitosan was sufficient to obtain enantioselection in the Michael addition of isobutyraldehyde to maleimides in the aqueous phase. Interestingly, the biopolymer afforded the opposite enantiomer in excess compared to the monomer, d-glucosamine. In this reaction, good correlation between the degree of deacetylation and the catalytic activity was found. These results are novel steps in the application of this natural, biocompatible and biodegradable polymer in developing environmentally benign methods for the production of optically pure fine chemicals.
Mechanochemical, Water-Assisted Asymmetric Transfer Hydrogenation of Ketones Using Ruthenium Catalyst
Kolcsár, Vanessza Judit,Sz?ll?si, Gy?rgy
, (2022/01/04)
Asymmetric catalytic reactions are among the most convenient and environmentally benign methods to obtain optically pure compounds. The aim of this study was to develop a green system for the asymmetric transfer hydrogenation of ketones, applying chiral Ru catalyst in aqueous media and mechanochemical energy transmission. Using a ball mill we have optimized the milling parameters in the transfer hydrogenation of acetophenone followed by reduction of various substituted derivatives. The scope of the method was extended to carbo- and heterocyclic ketones. The scale-up of the developed system was successful, the optically enriched alcohols could be obtained in high yields. The developed mechanochemical system provides TOFs up to 168 h?1. Our present study is the first in which mechanochemically activated enantioselective transfer hydrogenations were carried out, thus, may be a useful guide for the practical synthesis of optically pure chiral secondary alcohols.
Chiral amino-pyridine-phosphine tridentate ligand, manganese complex, and preparation method and application thereof
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Paragraph 0597-0600; 0605, (2020/07/13)
The invention discloses a chiral amino-pyridine-phosphine tridentate ligand, a manganese complex, and a preparation method and application thereof. The chiral amino-pyridine-phosphine tridentate ligand is shown as a formula II, and the manganese complex of the chiral amino-pyridine-phosphine tridentate ligand can be used for efficiently catalyzing and hydrogenating ketone compounds to prepare chiral alcohol compounds in a high enantioselectivity mode. The chiral amino-pyridine-phosphine tridentate ligand and the manganese complex are simple in synthesis process, good in stability, high in catalytic activity and mild in reaction conditions.
Highly Enantioselective Transfer Hydrogenation of Prochiral Ketones Using Ru(II)-Chitosan Catalyst in Aqueous Media
Sz?ll?si, Gy?rgy,Kolcsár, Vanessza Judit
, p. 820 - 830 (2018/12/13)
Unprecedentedly high enantioselectivities are obtained in the transfer hydrogenation of prochiral ketones catalyzed by a Ru complex formed in situ with chitosan chiral ligand. This biocompatible, biodegradable chiral polymer obtained from the natural chitin afforded good, up to 86 % enantioselectivities, in the aqueous-phase transfer hydrogenation of acetophenone derivatives using HCOONa as hydrogen donor. Cyclic ketones were transformed in even higher, over 90 %, enantioselectivities, whereas further increase, up to 97 %, was obtained in the transfer hydrogenations of heterocyclic ketones. The chiral catalyst precursor prepared ex situ was examined by scanning electron microscopy, FT-mid- and -far-IR spectroscopy. The structure of the in situ formed catalyst was investigated by 1H NMR spectroscopy and using various chitosan derivatives. It was shown that a Ru pre-catalyst is formed by coordination of the biopolymer to the metal by amino groups. This precursor is transformed in water insoluble Ru-hydride complex following hydrogen donor addition. The practical value of the developed method was verified by preparing over twenty chiral alcohols in good yields and optical purities. The catalyst was applied for obtaining optically pure chiral alcohols at gram scale following a single crystallization.
