621-87-4Relevant articles and documents
Catalytic Activity of Various Salts in the Reaction of 2,3-Epoxypropyl Phenyl Ether and Carbon Dioxide under Atmospheric Pressure
Kihara, Nobuhiro,Hara, Nobutaka,Endo, Takeshi
, p. 6198 - 6202 (1993)
Reaction of 2,3-epoxypropyl phenyl ether (1) with carbon dioxide was carried out under atmospheric pressure in N-methylpyrrolidinone (NMP) at 100 deg C in the presence of 5 mol percent of various salts to obtain a five-membered cyclic carbonate, 4-(phenoxymethyl)-1,3-dioxolan-2-one (2), selectively.Only halide salts showed high catalytic activity, and the order of intrinsic activity was found to be as follows: chloride > bromide > iodide which is the order of nucleophilicity of the anion.Furthermore, the order of the activity was found to be lithium salt > sodium salt > benzyltrimethylammonium salt, which is in accord with the order of Lewis acidity of the cation.Kinetic analyses show that the reaction rate can be represented by -d/dt=k, where the carbon dioxide pressure shows no effect on the reaction rate.The reaction proceeds via nucleophilic attack of halide to oxirane to form β-haloalkoxide 4 which reacts with CO2 followed by cyclization.The presence of key intermediate 4 was indirectly proved by the reaction of 1 with 1 equiv of LiBr in the absence of CO2 at 100 deg C for 2.5 h in NMP which leads to 1-phenoxy-2-propanone (6) in 20percent yield as the rearrangement product of 4.
Engineering the large pocket of an (S)-selective transaminase for asymmetric synthesis of (S)-1-amino-1-phenylpropane
Liu, He,Wang, Hualei,Wei, Dongzhi,Xie, Youyu,Xu, Feng,Xu, Xiangyang,Yang, Lin
, p. 2461 - 2470 (2021/04/22)
Amine transaminases offer an environmentally benign chiral amine asymmetric synthesis route. However, their catalytic efficiency towards bulky chiral amine asymmetric synthesis is limited by the natural geometric structure of the small pocket, representing a great challenge for industrial applications. Here, we rationally engineered the large binding pocket of an (S)-selective ?-transaminase BPTA fromParaburkholderia phymatumto relieve the inherent restriction caused by the small pocket and efficiently transform the prochiral aryl alkyl ketone 1-propiophenone with a small substituent larger than the methyl group. Based on combined molecular docking and dynamic simulation analyses, we identified a non-classical substrate conformation, located in the active site with steric hindrance and undesired interactions, to be responsible for the low catalytic efficiency. By relieving the steric barrier with W82A, we improved the specific activity by 14-times compared to WT. A p-p stacking interaction was then introduced by M78F and I284F to strengthen the binding affinity with a large binding pocket to balance the undesired interactions generated by F44. T440Q further enhanced the substrate affinity by providing a more hydrophobic and flexible environment close to the active site entry. Finally, we constructed a quadruple variant M78F/W82A/I284F/T440Q to generate the most productive substrate conformation. The 1-propiophenone catalytic efficiency of the mutant was enhanced by more than 470-times in terms ofkcat/KM, and the conversion increased from 1.3 to 94.4% compared with that of WT, without any stereoselectivity loss (ee > 99.9%). Meanwhile, the obtained mutant also showed significant activity improvements towards various aryl alkyl ketones with a small substituent larger than the methyl group ranging between 104- and 230-fold, demonstrating great potential for the efficient synthesis of enantiopure aryl alkyl amines with steric hindrance in the small binding pocket.
Selective aerobic oxidation of allyl phenyl ether to methyl ketone by palladium–polyoxometalate hybrid catalysts
Hong, Dachao,Kon, Yoshihiro,Shimoyama, Yoshihiro,Tamura, Satoru
, (2020/09/03)
In this study, we report that selective aerobic oxidation of allyl phenyl ethers is attained by a Pd catalyst/polyoxometalate hybrid system to yield corresponding methyl ketones in water-enriched acetonitrile. The Pd(OAc)2/H5PV2Mo10O40 system exhibits higher conversions and yields of corresponding methyl ketone by Wacker-type oxidation of allyl phenyl ether as compared with the conventional PdCl2/CuCl2 system. The higher yields are attributed to the efficient re-oxidation of Pd0 to Pd2+ by H5PV2Mo10O40 using O2 as an oxidant as evidenced by electrochemical measurements. A reduced species of H5PV2Mo10O40 by Pd0 during the catalytic oxidation is revealed by UV–vis spectral measurements. The use of PdCl2 in place of Pd(OAc)2 in combination with [PV2Mo10O40]5? bearing tetraalkylammonium counter cations has also exhibited comparable conversions and product yields in the Wacker-type oxidation of allyl phenyl ethers. Para-substituted allyl phenyl ether derivatives are successfully oxidized in the Pd catalyst/polyoxometalate system to yield corresponding methyl ketones. The initial rate of products of para-substituted methyl ketones depended on the electronic effect of the substituents in which allyl phenyl ethers with electron-donating groups have accelerated the initial rate in the Pd catalyst/polyoxometalate system.
Synthesis and Catalytic Properties of Metal- N-Heterocyclic-Carbene-Decorated Covalent Organic Framework
Dong, Ying,Dong, Yu-Bin,Kan, Jing-Lan,Li, Yue,Wu, Xiaowei
supporting information, p. 7363 - 7368 (2020/10/12)
We demonstrate herein that the N-heterocyclic-carbene (NHC)-metal complex (NHC-M)-involved covalent organic framework (COF) can be prepared by the direct polymerization of the NHC-M monomer with its counterpart under solvothermal conditions. The NHC-M-COF with different counterions is readily achieved via solid-state anion exchange. The obtained NHC-AuX-COF (X = Cl- and SbF6-) can be a highly active reusable catalyst to separately promote the carboxylation of the terminal alkyne with CO2 and alkyne hydration under mild conditions.
Synthesis of benzofurans from the cyclodehydration of α-phenoxy ketones mediated by Eaton’s reagent
Ma, Lin,Ma, Zhanwei,Zhang, Min,Zhou, Min
, p. 426 - 436 (2020/03/23)
Cyclodehydration of α-phenoxy ketones promoted by Eaton’s reagent (phosphorus pentoxide–methanesulfonic acid) is used to prepare 3-substituted or 2,3-disubstituted benzofurans with moderate to excellent yields under mild conditions. The method provides a facile access to benzofurans from readily available starting materials such as phenols and α-bromo ketones. The reaction is highly efficient, which is attributed to the good reactivity and fluidity of Eaton’s reagent. The reaction can be applied to prepare naphthofurans, furanocoumarins, benzothiophenes, and benzopyrans.
Selective Cross-Dehydrogenative C(sp3)-H Arylation with Arenes
Hao, Hong-Yan,Mao, Yang-Jie,Xu, Zhen-Yuan,Lou, Shao-Jie,Xu, Dan-Qian
supporting information, p. 2396 - 2402 (2020/03/13)
Selective C(sp3)-C(sp2) bond construction is of central interest in chemical synthesis. Despite the success of classic cross-coupling reactions, the cross-dehydrogenative coupling between inert C(sp3)-H and C(sp2)-H bonds represents an attractive alternative toward new C(sp3)-C(sp2) bonds. Herein, we establish a selective inter-and intramolecular C(sp3)-H arylation of alcohols with nondirected arenes that thereby provides a general pathway to access a wide range of β-arylated alcohols, including tetrahydronaphthalen-2-ols and benzopyran-3-ols, with high to excellent chemo-and regioselectivity.
Oxidation of alcohols using an oxoammonium salt bearing the nitrate anion
Miller, Shelli A.,Sandoval, Arturo León,Leadbeater, Nicholas E.
supporting information, (2019/12/25)
A methodology for the oxidation of alcohols to the corresponding carbonyl compounds is reported using a sub-stoichiometric quantity of an oxoammonium salt bearing the nitrate counterion. The approach proves successful for the oxidation of a range of alcohol substrates including those bearing an oxygen atom β to the site of oxidation or an α-trifluoromethyl moiety. The mechanism of the reaction has been probed and also gives an insight into the previously reported nitric acid mediated oxidation of alcohols.
Catalytic Oxidation of Alcohols Using a 2,2,6,6-Tetramethylpiperidine-N-hydroxyammonium Cation
Miller, Shelli A.,Bisset, Kathryn A.,Leadbeater, Nicholas E.,Eddy, Nicholas A.
supporting information, p. 1413 - 1417 (2019/01/04)
The oxidation of alcohols to aldehydes, ketones, and carboxylic acids is reported using 2,2,6,6-tetramethylpiperidine-4-acetamido-hydroxyammonium tetrafluoroborate as a catalyst in conjunction with sodium hypochlorite pentahydrate as a terminal oxidant. The reaction is generally complete within 30–120 min using an acetonitrile/water mix as the solvent, and no additives are required. Product yields are good to excellent and of particular note is that the methodology can be used to access aryl α-trifluoromethyl ketones.
TBAI/TBHP mediated oxidative cross coupling of ketones with phenols and carboxylic acids: Direct access to benzofurans
Santhosh Kumar,Ravikumar,Chinna Ashalu,Rajender Reddy
supporting information, p. 33 - 37 (2017/12/11)
TBAI/TBHP mediated oxidative cross coupling of phenols and carboxylic acids with ketones has been reported under metal-free, base free, solvent free conditions enabling environmentally benign synthesis of aryloxyketones, acyloxy ketones and benzofurans. Phenoxyketones and acyloxylcarbonyl compounds were synthesized in good to high yields, where as benzofurans were synthesized in moderate yields. This method is operationally simple, works under mild conditions, using commercially available as well as inexpensive TBAI and an oxidant TBHP.
Biocatalytic Racemization Employing TeSADH: Substrate Scope and Organic Solvent Compatibility for Dynamic Kinetic Resolution
Pop?oński, Jaros?aw,Reiter, Tamara,Kroutil, Wolfgang
, p. 763 - 768 (2018/02/27)
Racemization in combination with a kinetic resolution is the base for a dynamic kinetic resolution (DKR). Biocatalytic racemization was successfully performed for a broad scope of sec-alcohols by employing a single alcohol dehydrogenase (ADH) variant from Thermoanaerobacter pseudoethanolicus (formerly T. ethanolicus; TeSADH W110A I86A C295A). The catalyst employed as a lyophilized whole cell preparation or cell free extract, which tolerated various non-water miscible organic solvents under micro-aqueous or two-phase conditions, whereby cyclohexane and n-hexane suited best. Various concepts for combining the enzymatic racemization with an enzymatic kinetic resolution to achieve overall a bis-enzymatic DKR were evaluated. A proof of concept showed a successful DKR with racemization in aqueous phase combined with acylation in the organic phase.
