20681-51-0Relevant academic research and scientific papers
Rhodium-Catalyzed β-Dehydroborylation of Silyl Enol Ethers: Access to Highly Functionalized Enolates
Li, Jie,Li, Ruoling,Yang, Wen,Zhao, Pei,Zhao, Wanxiang
supporting information, p. 9580 - 9585 (2021/12/14)
An efficient rhodium-catalyzed β-dehydroborylation of aldehyde-derived silyl enol ethers (SEEs) with bis(pinacolato)diboron (B2pin2) is disclosed. The borylation reactions proceeded well with alkyl- and aryl-substituted SEEs, affording a wide array of valuable functionalized β-boryl silyl enolates with high efficiency and excellent stereoselectivity. Moreover, the borylated products, through versatile carbon–boron bond transformations, were readily converted into diverse synthetically useful molecules, including α-hydroxy ketones, functionalized SEEs, and gem-difunctionalized aldehydes.
Three-Component Alkene Difunctionalization by Direct and Selective Activation of Aliphatic C?H Bonds
Xu, Sheng,Chen, Herong,Zhou, Zhijun,Kong, Wangqing
supporting information, p. 7405 - 7411 (2021/02/20)
Catalytic alkene difunctionalization is a powerful strategy for the rapid assembly of complex molecules and has wide range of applications in synthetic chemistry. Despite significant progress, a compelling challenge that still needs to be solved is the installation of highly functionalized C(sp3)-hybridized centers without requiring pre-activated substrates. We herein report that inexpensive and easy-to-synthesize decatungstate photo-HAT, in combination with nickel catalysis, provides a versatile platform for three-component alkene difunctionalization through direct and selective activation of aliphatic C?H bonds. Compared with previous studies, the significant advantages of this strategy are that the most abundant hydrocarbons are used as feedstocks, and various highly functionalized tertiary, secondary, and primary C(sp3)-hybrid centers can be easily installed. The practicability of this strategy is demonstrated in the selective late-stage functionalization of natural products and the concise synthesis of pharmaceutically relevant molecules including Piragliatin.
Efficient C-H Amination Catalysis Using Nickel-Dipyrrin Complexes
Betley, Theodore A.,Clarke, Ryan M.,Dong, Yuyang,Porter, Gerard J.
supporting information, p. 10996 - 11005 (2020/07/08)
A dipyrrin-supported nickel catalyst (AdFL)Ni(py) (AdFL: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine) displays productive intramolecular C-H bond amination to afford N-heterocyclic products using aliphatic azide substrates. The catalytic amination conditions are mild, requiring 0.1-2 mol% catalyst loading and operational at room temperature. The scope of C-H bond substrates was explored and benzylic, tertiary, secondary, and primary C-H bonds are successfully aminated. The amination chemoselectivity was examined using substrates featuring multiple activatable C-H bonds. Uniformly, the catalyst showcases high chemoselectivity favoring C-H bonds with lower bond dissociation energy as well as a wide range of functional group tolerance (e.g., ethers, halides, thioetheres, esters, etc.). Sequential cyclization of substrates with ester groups could be achieved, providing facile preparation of an indolizidine framework commonly found in a variety of alkaloids. The amination cyclization reaction mechanism was examined employing nuclear magnetic resonance (NMR) spectroscopy to determine the reaction kinetic profile. A large, primary intermolecular kinetic isotope effect (KIE = 31.9 ± 1.0) suggests H-atom abstraction (HAA) is the rate-determining step, indicative of H-atom tunneling being operative. The reaction rate has first order dependence in the catalyst and zeroth order in substrate, consistent with the resting state of the catalyst as the corresponding nickel iminyl radical. The presence of the nickel iminyl was determined by multinuclear NMR spectroscopy observed during catalysis. The activation parameters (ΔH? = 13.4 ± 0.5 kcal/mol; ΔS?= -24.3 ± 1.7 cal/mol·K) were measured using Eyring analysis, implying a highly ordered transition state during the HAA step. The proposed mechanism of rapid iminyl formation, rate-determining HAA, and subsequent radical recombination was corroborated by intramolecular isotope labeling experiments and theoretical calculations.
TRICYCLIC COMPOUND SERVING AS IMMUNOMODULATOR
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Paragraph 0216-0217, (2019/01/04)
Provided are compounds of formula I and formula II or pharmaceutically acceptable salts of the compounds and pharmaceutical compositions thereof. The compounds of formula I and formula II or the pharmaceutically acceptable salts of the compounds provide indole 2,3-dioxygenase (IDO) inhibitory activity and are capable of treating IDO-mediated immunosuppressive diseases, such as infectious diseases or cancer.
Sunlight-driven trifluoromethylation of olefinic substrates by photoredox catalysis: A green organic process
Akita, Munetaka,Koike, Takashi
, p. 742 - 751 (2015/07/15)
The principles and utility of photoredox catalysis in organic synthesis are described. After a brief description of the features of the two types of catalytic photoredox processes following the reductive quenching cycle (RQC) and the oxidative quenching cycle (OQC), the discussion is focused on organic transformations based on OQC, in particular the trifluoromethylation of olefinic substrates with electrophilic trifluoromethylating reagents furnishing solvolytic addition products and substitution products. It is concluded that catalytic photoredox systems are green from the point of view of harmfulness, safety, and energy source (visible light, including sunlight). Future prospects of photoredox catalysis will be also discussed.
Synthesis of novel 3-cyclohexylpropanoic acid-derived nitrogen heterocyclic compounds and their evaluation for tuberculostatic activity
Gobis, Katarzyna,Foks, Henryk,Bojanowski, Krzysztof,Augustynowicz-Kope?, Ewa,Napiórkowska, Agnieszka
experimental part, p. 137 - 144 (2012/03/08)
A series of novel 3-cyclohexylpropanoic acid derivatives and 3-cyclohexylpropanoic acid-derived nitrogen heterocyclic compounds (1-8) have been synthesized and evaluated for tuberculostatic activity. Compounds 1a, 1c, 1e and 1f bearing benzimidazole or benzimidazole-like systems showed the most potent tuberculostatic activity against Mycobacterium tuberculosis strains with MIC values ranging from 1.5 to 12.5 μg/mL. More importantly 1a (6-chloro-2-(2-cyclohexylethyl)-4-nitro-1H-benzo[d]imidazole) and 1f (2-(2-cyclohexylethyl)-1H-imidazo[4,5-b]phenazine) appeared selective for M. tuberculosis as compared with eukaryotic cells (human fibroblasts), and other antimicrobial strains. These compounds may thus represent a novel, selective class of antitubercular agents. Additionally compound 1a stimulated type I collagen output by fibroblasts, in vitro.
Visible light-induced selective generation of radicals from organoborates by photoredox catalysis
Yasu, Yusuke,Koike, Takashi,Akita, Munetaka
, p. 3414 - 3420 (2013/02/25)
A new strategy for the generation of carbon-centered radicals via oxidation of alkyl-, allyl-, benzyl- and arylborates by visible-light-driven single electron transfer (SET) photoredox catalysis has been established. The generated radicals smoothly react with TEMPO and electron-deficient alkenes to afford C-O and C-C coupling products, respectively. In this radical initiating system, cyclic organo(triol)borates turn out to be useful radical precursors.
A simple and highly effective method for hydrogenation of arenes by [Rh(COD)Cl]2
Wang, Da-Wei,Lu, Sheng-Mei,Zhou, Yong-Gui
supporting information; experimental part, p. 1282 - 1285 (2009/09/06)
Hydrogenation of arenes, including chiral BINOLs and the lignin model compounds, has been achieved efficiently by using the simple complex [Rh(COD)Cl]2 as catalyst precursor.
Tetrabutylammonium decatungstate-photosensitized alkylation of electrophilic alkenes: Convenient functionalization of aliphatic C-H bonds
Dondi, Daniele,Fagnoni, Maurizio,Albini, Angelo
, p. 4153 - 4163 (2007/10/03)
Tetrabutylammonium decatungstate (TBADT, 2×10-3M) is an effective photocatalyst for the alkylation of electrophilic alkenes (0.1 M, α,β-unsaturated nitriles, esters, ketones) by alkanes, alcohols, and ethers. The products are in most cases obtained in >70% isolated yields, through an experimentally very simple procedure. The kinetics of the radical processes following initial hydrogen abstraction by excited TBADT in deoxygenated MeCN have been studied. In the absence of a trap, back hydrogen transfer from reduced tungstate is the main pathway for alkyl radicals, while α-hydroxyalkyl radicals are oxidized to ketones by ground-state TBADT. With both radical types the reaction ceases at a few percent conversion. However, trapping by electrophilic alkenes is followed by reduction of the radical adduct and regeneration of the catalyst, which allows the alkylation to proceed up to complete alkene conversion with the mentioned good yields of products. With a nucleophilic (α-hydroxyalkyl) radical, alkylation is efficient (Φ = 0.58) and can also be carried out when degassing is omitted, the only difference being a short induction period. With a less reactive (cyclohexyl) radical, the quantum yield is lower (Φ = 0.06) and the reaction is considerably slowed in aerated solutions, but the chemical yield remains good.
Solvent-modulated chemoselective deprotections of trialkylsilyl esters and chemoselective esterifications
Lee, Adam Shih-Yuan,Su, Feng-Yih
, p. 6305 - 6309 (2007/10/03)
A series of trialkylsilyl esters were deprotected or transesterificated into their corresponding carboxylic acids or methyl esters under a catalytic amount of CBr4 in alcohol reaction system. This method enables to desilylate secondary sp3-carbon, sp2-carbon, sp-carbon and aryl tethered trialkylsilyl esters to carboxylic acids, whereas primary sp 3-carbon tethered trialkylsilyl esters were further converted into their methyl esters under CBr4/MeOH reaction conditions. The highly chemoselective deprotections can be modulated and achieved by the introduced protecting trialkylsilyl groups and the used alcohols such as MeOH and EtOH under this photochemically-induced reaction conditions.
