34281-94-2Relevant articles and documents
Aqueous chemoenzymatic one-pot enantioselective synthesis of tertiary α-aryl cycloketonesviaPd-catalyzed C-C formation and enzymatic C=C asymmetric hydrogenation
Luan, Pengqian,Liu, Yunting,Li, Yongxing,Chen, Ran,Huang, Chen,Gao, Jing,Hollmann, Frank,Jiang, Yanjun
, p. 1960 - 1964 (2021/03/26)
An aqueous chemoenzymatic cascade reaction combining Pd-catalyzed C-C formation and enzymatic C=C asymmetric hydrogenation (AH) was developed for enantioselective synthesis of tertiary α-aryl cycloketones in good yields and excellent enantioselectivities. The stereopreference of the enzyme in AH of α-aryl cyclohexenones was studied. An enantiocomplementary enzyme was obtained by site-directed mutation.
The Silicon-Hydrogen Exchange Reaction: Catalytic Kinetic Resolution of 2-Substituted Cyclic Ketones
List, Benjamin,Zhang, Pinglu,Zhou, Hui
supporting information, p. 1953 - 1956 (2021/11/17)
We have recently reported the strong and confined, chiral acid-catalyzed asymmetric 'silicon-hydrogen exchange reaction'. One aspect of this transformation is that it enables access to enantiopure enol silanes in a tautomerizing σ-bond metathesis, via deprotosilylation of ketones with allyl silanes as the silicon source. However, until today, this reaction has not been applied to racemic, 2-substituted, cyclic ketones. We show here that these important substrates readily undergo a highly enantioselective kinetic resolution furnishing the corresponding kinetically preferred enol silanes. Mechanistic studies suggest the fascinating possibility of advancing the process to a dynamic kinetic resolution.
The Silicon-Hydrogen Exchange Reaction: A Catalytic σ-Bond Metathesis Approach to the Enantioselective Synthesis of Enol Silanes
Zhou, Hui,Bae, Han Yong,Leutzsch, Markus,Kennemur, Jennifer L.,Bécart, Diane,List, Benjamin
, p. 13695 - 13700 (2020/08/24)
The use of chiral enol silanes in fundamental transformations such as Mukaiyama aldol, Michael, and Mannich reactions as well as Saegusa-Ito dehydrogenations has enabled the chemical synthesis of enantiopure natural products and valuable pharmaceuticals. However, accessing these intermediates in high enantiopurity has generally required the use of either stoichiometric chiral precursors or stoichiometric chiral reagents. We now describe a catalytic approach in which strongly acidic and confined imidodiphosphorimidates (IDPi) catalyze highly enantioselective interconversions of ketones and enol silanes. These "silicon-hydrogen exchange reactions"enable access to enantiopure enol silanes via tautomerizing σ-bond metatheses, either in a deprotosilylative desymmetrization of ketones with allyl silanes as the silicon source or in a protodesilylative kinetic resolution of racemic enol silanes with a carboxylic acid as the silyl acceptor.
HPLC with cellulose Tris (3,5-DimethylPhenylcarbamate) chiral stationary phase: Influence of coating times and coating amount on chiral discrimination
Wei, Qiuhong,Su, Hongjiu,Gao, Diannan,Wang, Shudong
, p. 164 - 173 (2019/01/18)
Coating cellulose tris (3,5-dimethylphenylcarbamate) (CDMPC) on silica gels with large pores have been demonstrated as an efficient way for the preparation of chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC). During the process, a number of parameters, including the type of coating solvent, amount of coating, and the method for subsequent solvent removing, have been proved to affect the performance of the resultant CSPs. Coating times and the concentration of coating solution, however, also makes a difference to CSPs' performance by changing the arrangement of cellulose derivatives while remaining the coating amount constant, have much less been studied before, and thereby, were systematically investigated in this work. Results showed that CSPs with more coating times exhibited higher chiral recognition and column efficiency, suggesting that resolution was determined by column efficiency herein. Afterwards, we also investigated the effect of coating amount on the performance of CSPs, and it was shown that the ability of enantio-recognition did not increase all the time as the coating amount; and four of seven racemates achieved best resolution when the coating amount reached to 18.37%. At the end, the reproducibility of CDMPC-coated CSPs were further confirmed by two methods, ie, reprepared the CSP-0.15-3 and reevaluated the effect of coating times.
Enantioselective Protonation of Silyl Enol Ethers Catalyzed by a Chiral Pentacarboxycyclopentadiene-Based Bronsted Acid
An, Shaoyu,Li, Jun,Li, Pingfan,Yuan, Chao
, p. 1317 - 1320 (2019/06/19)
The enantioselective protonation of silyl enol ethers was realized in the presence of a pentacarboxycyclopenta-1,3-diene-based chiral Bronsted acid catalyst with water as an achiral proton source to give the corresponding α-aryl ketones in good yields and up to 75percent ee.
Safe and Scalable Aerobic Oxidation by 2-Azaadamantan-2-ol (AZADOL)/NOx Catalysis: Large-Scale Preparation of Shi's Catalyst
Sasano, Yusuke,Sato, Hikaru,Tadokoro, Shinsuke,Kozawa, Masami,Iwabuchi, Yoshiharu
, p. 571 - 577 (2019/03/19)
A method for safe and scalable aerobic alcohol oxidation using 2-azaadamantan-2-ol (AZADOL), an azaadamantane-type hydroxylamine catalyst, with a NOx cocatalyst in a conventional batch reactor has been developed. The use of 2 mol % AZADOL and 10 mol % NaNO2 was determined to promote aerobic alcohol oxidation quantitatively within a reasonable time (8 h). Safety is ensured by controlling the reaction temperature below the flash point of the acetic acid solvent. The robustness of the developed method is demonstrated by the 500 g scale oxidation of diacetone fructose into Shi's catalyst for asymmetric epoxidation.
Amino-TEMPO Grafted on Magnetic Multi-Walled Nanotubes: An Efficient and Recyclable Heterogeneous Oxidation Catalyst
Gambarotti, Cristian,Bj?rsvik, Hans-René
, p. 1405 - 1412 (2019/01/04)
An efficient and easy recyclable heterogeneous oxidation catalyst was prepared by grafting TEMPO–NH2 moieties on the surface of magnetic multi-walled carbon nanotubes (MWCNT), first by a radical reaction introducing butyric acid moieties on carbon nanotube surface. Subsequently, carboxylic acid moieties were submitted for amidation using TEMPO–NH2. The functionalized nanotubes [MWCNT-{(CH2)3-CO-NH-TEMPO}n] were investigated as a (pre-)catalyst for the oxidation of primary and secondary alcohols for the production of aldehydes and ketones in a Montanari-type catalytic oxidation using the cheap and readily available 1,3-dichloro-5,5-dimethylhydantoin as the terminal oxidant.
Chiral isoxazolidine-mediated stereoselective umpolung α-phenylation of methyl ketones
Takeda, Norihiko,Furuishi, Mizuki,Nishijima, Yuri,Futaki, Erika,Ueda, Masafumi,Shinada, Tetsuro,Miyata, Okiko
supporting information, p. 8940 - 8943 (2018/12/10)
An effective asymmetric α-phenylation of methyl ketones with triphenylaluminium in the presence of (+)-benzopyranoisoxazolidine has been developed. The reaction proceeds via the in situ formation of a chiral N-alkoxyenamine and the subsequent diastereoselective nucleophilic phenylation to provide α-phenylated products in moderate to good yields, with high enantioselectivities.
Cellulose type chiral stationary phase based on reduced graphene oxide@silica gel for the enantiomer separation of chiral compounds
Li, Yuanyuan,Li, Qiang,Zhu, Nan,Gao, Zhuxian,Ma, Yulong
, p. 996 - 1004 (2018/07/29)
The graphene oxide (GO) was covalently coupled to the surfaces of silica gel (SiO2) microspheres by amide bond to get the graphene oxide@silica gel (GO@SiO2). Then, the GO@SiO2 was reduced with hydrazine to the reduced graphene oxide@silica gel (rGO@SiO2), and the cellulose derivatives were physically coated on the surfaces of rGO@SiO2 to prepare a chiral stationary phase (CSP) for high performance liquid chromatography. Under the optimum experimental conditions, eight benzene-enriched enantiomers were separated completely, and the resolution of trans-stilbene oxide perfectly reached 4.83. Compared with the blank column of non-bonded rGO, the separation performance is better on the new CSP, which is due to the existence of rGO to produce special retention interaction with analytes, such as π-π stacking, hydrophobic effect, π-π electron-donor–acceptor interaction, and hydrogen bonding. Therefore, the obtained CSP shows special selectivity for benzene-enriched enantiomers, improves separation selectivity and efficiency, and rGO plays a synergistic effect with cellulose derivatives on enantioseparation.
First chemo-enzymatic synthesis of the (R)-Taniguchi lactone and substrate profiles of CAMO and OTEMO, two new Baeyer–Villiger monooxygenases
Rudroff, Florian,Fink, Michael J.,Pydi, Ramana,Bornscheuer, Uwe T.,Mihovilovic, Marko D.
, p. 157 - 165 (2017/01/17)
Abstract: This study investigates the substrate profile of cycloalkanone monooxygenase and 2-oxo-Δ3-4,5,5-trimethylcyclopentenylacetyl-coenzyme A monooxygenase, two recently discovered enzymes of the Baeyer–Villiger monooxygenase family, used as whole-cell biocatalysts. Biooxidations of a diverse set of ketones were performed on analytical scale: desymmetrization of substituted prochiral cyclobutanones and cyclohexanones, regiodivergent oxidation of terpenones and bicyclic ketones, as well as kinetic resolution of racemic cycloketones. We demonstrated the applicability of the title enzymes in the enantioselective synthesis of (R)-(?)-Taniguchi lactone, a building block for the preparation of various natural product analogs such as ent-quinine. Graphical abstract: [Figure not available: see fulltext.]
