938-37-4Relevant academic research and scientific papers
Switching between mono and doubly reduced odd alternant hydrocarbon: designing a redox catalyst
Ahmed, Jasimuddin,Datta, Paramita,Das, Arpan,Jomy, Stephy,Mandal, Swadhin K.
, p. 3039 - 3049 (2021/03/14)
Since the early Hückel molecular orbital (HMO) calculations in 1950, it has been well known that the odd alternant hydrocarbon (OAH), the phenalenyl (PLY) system, can exist in three redox states: closed shell cation (12π e?), mono-reduced open shell neutral radical (13π e?) and doubly reduced closed shell anion (14π e?). Switching from one redox state of PLY to another leads to a slight structural change owing to its low energy of disproportionation making the electron addition or removal process facile. To date, mono-reduced PLY based radicals have been extensively studied. However, the reactivity and application of doubly reduced PLY species have not been explored so far. In this work, we report the synthesis of the doubly reduced PLY species (14π e?) and its application towards the development of redox catalysisviaswitching with the mono-reduced form (13π e?) for aryl halide activation and functionalization under transition metal free conditions without any external stimuli such as heat, light or cathodic current supply.
Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity**
Chernowsky, Colleen P.,Chmiel, Alyah F.,Wickens, Zachary K.
, p. 21418 - 21425 (2021/08/25)
Herein, we disclose that electrochemical stimulation induces new photocatalytic activity from a range of structurally diverse conventional photocatalysts. These studies uncover a new electron-primed photoredox catalyst capable of promoting the reductive cleavage of strong C(sp2)?N and C(sp2)?O bonds. We illustrate several examples of the synthetic utility of these deeply reducing but otherwise safe and mild catalytic conditions. Finally, we employ electrochemical current measurements to perform a reaction progress kinetic analysis. This technique reveals that the improved activity of this new system is a consequence of an enhanced catalyst stability profile.
Metal-Free Photoredox-Catalyzed Hydrodefluorination of Fluoroarenes Utilizing Amide Solvent as Reductant
Toriumi, Naoyuki,Yamashita, Kazuya,Iwasawa, Nobuharu
, p. 12635 - 12641 (2021/08/03)
A metal-free photoredox-catalyzed hydrodefluorination of fluoroarenes was achieved by using N,N,N’,N’-tetramethyl-para-phenylenediamine (1) as a strong photoreduction catalyst. This reaction was applicable not only to electron-rich monofluoroarenes but also to polyfluoroarenes to afford non-fluorinated arenes. The experimental mechanistic studies indicated that the amide solvent NMP plays an important role for regeneration of the photocatalyst, enabling additive-free photoreduction catalysis.
A case of chain propagation: α-aminoalkyl radicals as initiators for aryl radical chemistry
Constantin, Timothée,Juliá, Fabio,Leonori, Daniele,Sheikh, Nadeem S.
, p. 12822 - 12828 (2020/12/29)
The generation of aryl radicals from the corresponding halides by redox chemistry is generally considered a difficult task due to their highly negative reduction potentials. Here we demonstrate that α-aminoalkyl radicals can be used as both initiators and chain-carriers for the radical coupling of aryl halides with pyrrole derivatives, a transformation often employed to evaluate new highly reducing photocatalysts. This mode of reactivity obviates for the use of strong reducing species and was also competent in the formation of sp2 C-P bonds. Mechanistic studies have delineated some of the key features operating that trigger aryl radical generation and also propagate the chain process.
Potent Reductants via Electron-Primed Photoredox Catalysis: Unlocking Aryl Chlorides for Radical Coupling
Chernowsky, Colleen P.,Cowper, Nicholas G. W.,Wickens, Zachary K.,Williams, Oliver P.
supporting information, (2020/02/04)
We describe a new catalytic strategy to transcend the energetic limitations of visible light by electrochemically priming a photocatalyst prior to excitation. This new catalytic system is able to productively engage aryl chlorides with reduction potentials hundreds of millivolts beyond the potential of Na0 in productive radical coupling reactions. The aryl radicals produced via this strategy can be leveraged for both carbon-carbon and carbon-heteroatom bond-forming reactions. Through direct comparison, we illustrate the reactivity and selectivity advantages of this approach relative to electrolysis and photoredox catalysis.
Generation of Aryl Radicals from Aryl Halides: Rongalite-Promoted Transition-Metal-Free Arylation
Yu, Fazhi,Mao, Runyu,Yu, Mingcheng,Gu, Xianfeng,Wang, Yonghui
, p. 9946 - 9956 (2019/09/04)
A new and practical method for the generation of aryl radicals from aryl halides is reported. Rongalite as a novel precursor of super electron donors was used to initiate a series of electron-catalyzed reactions under mild conditions. These transition-metal-free radical chain reactions enable the efficient formation of C-C, C-S, and C-P bonds through homolytic aromatic substitution or SRN1 reactions. Moreover, the synthesis of antipsychotic drug Quetiapine was performed on gram scale through the described method. This protocol demonstrated its potential as a promising arylation method in organic synthesis.
Determination of the inhibitory effects of N-methylpyrrole derivatives on glutathione reductase enzyme
Kocao?lu, Esma,Talaz, Oktay,?avdar, Hüseyin,?entürk, Murat,Supuran, Claudiu T.,Ekinci, Deniz
, p. 51 - 54 (2018/10/31)
Glutathione reductase (GR) is a crucial antioxidant enzyme which is responsible for the maintenance of antioxidant GSH molecule. Antimalarial effects of some chemical molecules are attributed to their inhibition of GR, thus inhibitors of this enzyme are expected to be promising candidates for the treatment of malaria. In this work, GR inhibitory properties of N-Methylpyrrole derivatives are reported. It was found that all compounds have better inhibitory activity than the strong GR inhibitor N,N-bis(2-chloroethyl)-N-nitrosourea, especially three molecules, 8 m, 8?n, and 8?q, were determined to be the most powerful among them. Findings of our study indicates that these Schiff base derivatives are strong GR inhibitors which can be used as leads for designation of novel antimalarial candidates.
Temperature Controlled Selective C-S or C-C Bond Formation: Photocatalytic Sulfonylation versus Arylation of Unactivated Heterocycles Utilizing Aryl Sulfonyl Chlorides
Pagire, Santosh K.,Hossain, Asik,Reiser, Oliver
supporting information, p. 648 - 651 (2018/02/09)
A visible-light-induced photocatalytic method for the arylsulfonylation of heterocycles has been developed. The synthetic utility of this reaction is reflected by the direct use of commercially available sulfonyl chlorides and heterocycles under room temperature conditions. Complementarily, the photocatalytic arylation of heterocycles by sulfonyl chlorides via extrusion of SO2 is feasible at elevated temperature conditions, allowing switching between arylation or arylsulfonylation with excellent chemoselectivity.
Lanthanide Ions Coupled with Photoinduced Electron Transfer Generate Strong Reduction Potentials from Visible Light
Meyer, Andreas Uwe,Slanina, Tomá?,Heckel, Alexander,K?nig, Burkhard
supporting information, p. 7900 - 7904 (2017/06/19)
Metal ions can have beneficial effects on photoinduced electron transfer. Merging such metal-ion-coupled electron transfer (MCET) with consecutive photoinduced electron transfer (conPET) enables the one-electron reduction of chlorobenzene with blue light in the presence of diisopropylethylamine as an electron donor. The presence of the metal ions extends the substrate scope of the photoredox catalysis to extreme reduction potentials (beyond ?3 V vs. SCE).
Selective synthesis of pyrrolo[1,2-a] azepines or 4,6-dicarbonyl indoles via tandem reactions of alkynones with pyrrole derivatives
Zhao, Yulei,Yuan, Yang,Xu, Murong,Zheng, Zhong,Zhang, Runhua,Li, Yanzhong
supporting information, p. 6328 - 6332 (2017/08/10)
Novel methodologies for the selective synthesis of pyrrolo[1,2-a]azepines or 4,6-dicarbonyl indoles starting from pyrrole derivatives and alkynones are described. When reactions were carried out with 1,2,4-trisubstituted N-propargyl pyrroles using a ZnI2 catalyst, pyrrolo[1,2-a]azepines were obtained. Whereas 4,6-dicarbonyl indoles were produced selectively with 1,2-disubstituted pyrroles in the presence of silica gel. The reaction outcomes depend on the substituent pattern of the substrates and the nature of the catalysts chosen. Control reactions suggested that the formation of a conjugated enamine intermediate was crucial for both the processes. With easily accessible starting materials, inexpensive catalysts and an easy-to-handle procedure, this reaction has the potential to become a general protocol for the synthesis of pyrrolo[1,2-a]azepines or indoles.
