5773-56-8Relevant academic research and scientific papers
Standardization and Control of Grignard Reactions in a Universal Chemical Synthesis Machine using online NMR
Angelone, Davide,Bornemann-Pfeiffer, Martin,Cronin, Leroy,Emmerling, Franziska,Kern, Simon,Leonov, Artem,Meyer, Klas,Wolf, Jakob
, p. 23202 - 23206 (2021)
A big problem with the chemistry literature is that it is not standardized with respect to precise operational parameters, and real time corrections are hard to make without expert knowledge. This lack of context means difficult reproducibility because many steps are ambiguous, and hence depend on tacit knowledge. Here we present the integration of online NMR into an automated chemical synthesis machine (CSM aka. “Chemputer” which is capable of small-molecule synthesis using a universal programming language) to allow automated analysis and adjustment of reactions on the fly. The system was validated and benchmarked by using Grignard reactions which were chosen due to their importance in synthesis. The system was monitored in real time using online-NMR, and spectra were measured continuously during the reactions. This shows that the synthesis being done in the Chemputer can be dynamically controlled in response to feedback optimizing the reaction conditions according to the user requirements.
Reductive ring opening of cis- and trans-2,3-diphenyloxirane: A common intermediate
Yus, Miguel,MacIá, Beatriz,Gómez, Cecilia,Soler, Tatiana,Falvello, Larry R.,Fanwick, Phillip E.
, p. 3865 - 3871 (2005)
The reaction of both cis- and trans-2,3-diphenyloxirane (7 and 4, respectively) with an excess of lithium and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 2.5 mol%) in the presence of different carbonyl compounds as electrophiles (Barbier conditions) in THF at temperatures ranging between -80 and -50°C gives the same organolithium intermediate 5 and consequently, the same 1,3-diols 6. In the case of cis-epoxide an inversion of the configuration at the benzylic carbanionic center can explain the obtained results. Only for the dicyclopropyl ketone derivative (6h) some amount (14%) of the corresponding epimer (6′h) resulting from a process with retention of the configuration of the intermediate is obtained. In representative cases, the structure of the final products (6) was unequivocally determined by X-ray diffraction analysis.
Tropylium-Promoted Hydroboration Reactions: Mechanistic Insights Via Experimental and Computational Studies
Mai, Binh Khanh,Nguyen, Thanh Vinh,Ton, Nhan N. H.
, p. 9117 - 9133 (2021/07/19)
Hydroboration reaction of alkynes is one of the most synthetically powerful tools to access organoboron compounds, versatile precursors for cross-coupling chemistry. This type of reaction has traditionally been mediated by transition-metal or main group catalysts. Herein, we report a novel method using tropylium salts, typically known as organic oxidants and Lewis acids, to promote the hydroboration reaction of alkynes. A broad range of vinylboranes can be easily accessed via this metal-free protocol. Similar hydroboration reactions of alkenes and epoxides can also be efficiently catalyzed by the same tropylium catalysts. Experimental studies and DFT calculations suggested that the reaction follows an uncommon mechanistic pathway, which is triggered by the hydride abstraction of pinacolborane with tropylium ion. This is followed by a series ofin situcounterion-activated substituent exchanges to generate boron intermediates that promote the hydroboration reaction.
INHIBITORS OF NOROVIRUS AND CORONAVIRUS REPLICATION
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Paragraph 00534-00536, (2021/10/15)
Compounds of Formula (I) and methods of inhibiting the replication of viruses in a biological sample or patient, of reducing the amount of viruses in a biological sample or patient, and of treating a virus infection in a patient, comprising administering to said biological sample or patient an effective amount of a compound represented by Formula (I), a compound of Table A or B or a pharmaceutically acceptable salt thereof.
Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
Oestreich, Martin,Seliger, Jan
supporting information, 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.
Palladium-catalyzed synthesis of α-aryl acetophenones from styryl ethers and aryl diazonium saltsviaregioselective Heck arylation at room temperature
Kandasamy, Jeyakumar,Lee, Yong Rok,Singh, Adesh Kumar,Venkatesh, Rapelly
supporting information, p. 7832 - 7837 (2021/09/28)
Preparation of α-aryl acetophenones from styryl ethers and aryldiazonium salts is described. The reaction is catalyzed by palladium acetate at room temperature in the absence of ligand and base. The developed method is highly attractive in terms of reaction conditions, substrate scope, functional group tolerance and yields. Synthetic applications of the present method are demonstrated by preparing α-aryl indoles and 3-aryl isocoumarin from styryl ethers.
Half-sandwich rhodium complexes with phenylene-based SCS ligands: Synthesis, characterization and catalytic activities for transfer hydrogenation of ketones
Jia, Wei-Guo,Gao, Li-Li,Zhi, Xue-Ting,Li, Xiao-Dong,Wang, Zhi-Bao,Sun, Ying
, (2020/12/30)
A series of half-sandwich rhodium complexes with tridentate phenylene-based bis(thione) (SCS) ligand have been synthesized and characterized. Both half-sandwich rhodium complexes and phenylene-based bis(thione) compounds were fully characterized by 1H and 13C NMR spectra, mass spectrometry and single-crystal X-ray diffraction method. The catalytic activities of half-sandwich rhodium complexes toward the transfer hydrogenation of ketones to their corresponding alcohols were explored using 2-propanol as hydrogen source and solvent. And the half-sandwich rhodium complexes exhibited high catalytic activity for transfer hydrogenation of ketones with a broad functional group tolerance.
Highly efficient Meerwein-Ponndorf-Verley reductions over a robust zirconium-organoboronic acid hybrid
Song, Jinliang,Hua, Manli,Huang, Xin,Visa, Aurelia,Wu, Tianbin,Fan, Honglei,Hou, Minqiang,Zhang, Zhaofu,Han, Buxing
, p. 1259 - 1265 (2021/02/26)
The Meerwein-Ponndorf-Verley (MPV) reaction is an attractive approach to selectively reduce carbonyl groups, and the design of advanced catalysts is the key for these kinds of interesting reactions. Herein, we fabricated a novel zirconium organoborate using 1,4-benzenediboronic acid (BDB) as the precursor for MPV reduction. The prepared Zr-BDB had excellent catalytic performance for the MPV reduction of various biomass-derived carbonyl compounds (i.e., levulinate esters, aldehydes and ketones). More importantly, the number of borate groups on the ligands significantly affected the catalytic activity of the Zr-organic ligand hybrids, owing to the activation role of borate groups on hydroxyl groups in the hydrogen source. Detailed investigations revealed that the excellent performance of Zr-BDB was contributed by the synergetic effect of Zr4+and borate. Notably, this is the first work to enhance the activity of Zr-based catalysts in MPV reactions using borate groups.
Structural characterization of a square planar Ni(II) complex and its application as a catalyst for the transfer hydrogenation of ketones
Bala, Muhammad D.,Kadafour, Attahir N. W.
, (2021/12/01)
A new 2-hydroxy-1-naphthaldehyde Schiff base derived nickel(II) complex (4) was synthesized and fully characterized. Analysis of the structure of 4 by single-crystal X-ray diffraction shows two chelating Schiff base ligands bound to nickel in a trans [O∧N(Ni2+)N∧O] fashion. Hence, in a molecule of 4, two ligands are four coordinate to a Ni(II) center through the imine nitrogen and naphthyloxyl oxygen atoms. This coordination mode resulted in a square planar complex that is stabilized in the solid-state by a network of intermolecular O-H···N hydrogen bonds between neighboring molecules. The 1H NMR data showed the loss of the hydroxyl (OH) proton signal and an upfield shift of the metal-bound imine (-NH) proton signal, while the IR data also showed a lower energy shift in the absorption frequency of the imine (C = N) bond due to back donation from the coordinated Ni(II) center. As a catalyst for the transfer hydrogenation of a range of ketones, 4 showed good catalytic activity at a very low concentration of 0.1 mol% with 2-propanol as the model substrate. The catalyst is also effective for various related ketone substrates bearing a range of steric and electronic regulating groups.
Cobalt Catalyst Determines Regioselectivity in Ring Opening of Epoxides with Aryl Halides
Potrz?saj, Aleksandra,Musiejuk, Mateusz,Cha?adaj, Wojciech,Giedyk, Maciej,Gryko, Dorota
supporting information, p. 9368 - 9376 (2021/06/28)
Ring-opening of epoxides furnishing either linear or branched products belongs to the group of classic transformations in organic synthesis. However, the regioselective cross-electrophile coupling of aryl epoxides with aryl halides still represents a key challenge. Herein, we report that the vitamin B12/Ni dual-catalytic system allows for the selective synthesis of linear products under blue-light irradiation, thus complementing methodologies that give access to branched alcohols. Experimental and theoretical studies corroborate the proposed mechanism involving alkylcobalamin as an intermediate in this reaction.
