62154-11-4Relevant academic research and scientific papers
Electro-reductive Fragmentation of Oxidized Lignin Models
Yang, Cheng,Magallanes, Gabriel,Maldonado, Stephen,Stephenson, Corey R. J.
, p. 15927 - 15934 (2021/06/30)
Lignin provides a potential sustainable source for production of electron-rich aromatic compounds. Recently, electrochemical lignin degradation via an oxidation/reduction sequence under mild conditions has garnered much attention within the lignin community, as electrochemistry simplifies redox reactions and offers an electron source/sink for synthesis without using stoichiometric oxidants or reductants. This paper describes a fundamental approach for the electrochemical fragmentation of the primary connection in native lignin, β-O-4. Potential-controlled electrolysis enables selective reduction and provides fragmentation products and/or coupling products in isolated yields of 59-92%.
Reductive Coupling of Aromatic Aldehydes and Ketones under Electrochemical Conditions
Li, Qian-Yu,Swaroop, Toreshettahally R.,Wang, Heng Shan,Wang, Zi-Qiang
, (2020/04/27)
Reductive coupling of o-substituted carbonyl compounds and m-substituted carbonyl compounds by the direct transfer of electron to carbonyl group respectively gave 1-(4-(1-hydroxy-1-phenylethyl/methyl)phenyl)ethanones/methanones and 2,3-bis(3-substitutedph
GaN nanowires as a reusable photoredox catalyst for radical coupling of carbonyl under blacklight irradiation
Botton, Gianluigi,Cen, Yunen,Cheng, Shaobo,Li, Chao-Jun,Liu, Mingxin,Mi, Zetian,Rashid, Roksana T.,Tan, Lida
, p. 7864 - 7870 (2020/08/19)
Employing photo-energy to drive the desired chemical transformation has been a long pursued subject. The development of homogeneous photoredox catalysts in radical coupling reactions has been truly phenomenal, however, with apparent disadvantages such as the difficulty in separating the catalyst and the frequent requirement of scarce noble metals. We therefore envisioned the use of a hyper-stable III-V photosensitizing semiconductor with a tunable Fermi level and energy band as a readily isolable and recyclable heterogeneous photoredox catalyst for radical coupling reactions. Using the carbonyl coupling reaction as a proof-of-concept, herein, we report a photo-pinacol coupling reaction catalyzed by GaN nanowires under ambient light at room temperature with methanol as a solvent and sacrificial reagent. By simply tuning the dopant, the GaN nanowire shows significantly enhanced electronic properties. The catalyst showed excellent stability, reusability and functional tolerance. All reactions could be accomplished with a single piece of nanowire on Si-wafer. This journal is
Light-enabled metal-free pinacol coupling by hydrazine
Qiu, Zihang,Pham, Hanh D. M.,Li, Jianbin,Li, Chen-Chen,Castillo-Pazos, Durbis J.,Khaliullin, Rustam Z.,Li, Chao-Jun
, p. 10937 - 10943 (2019/12/23)
Efficient carbon-carbon bond formation is of great importance in modern organic synthetic chemistry. The pinacol coupling discovered over a century ago is still one of the most efficient coupling reactions to build the C-C bond in one step. However, traditional pinacol coupling often requires over-stoichiometric amounts of active metals as reductants, causing long-lasting metal waste issues and sustainability concerns. A great scientific challenge is to design a metal-free approach to the pinacol coupling reaction. Herein, we describe a light-driven pinacol coupling protocol without use of any metals, but with N2H4, used as a clean non-metallic hydrogen-atom-transfer (HAT) reductant. In this transformation, only traceless non-toxic N2 and H2 gases were produced as by-products with a relatively broad aromatic ketone scope and good functional group tolerance. A combined experimental and computational investigation of the mechanism suggests that this novel pinacol coupling reaction proceeds via a HAT process between photo-excited ketone and N2H4, instead of the common single-electron-transfer (SET) process for metal reductants.
Lewis Acid Assisted Electrophilic Fluorine-Catalyzed Pinacol Rearrangement of Hydrobenzoin Substrates: One-Pot Synthesis of (±)-Latifine and (±)-Cherylline
Shi, Hui,Du, Chuan,Zhang, Xinhang,Xie, Fukai,Wang, Xiaoyu,Cui, Shanshan,Peng, Xiaoshi,Cheng, Maosheng,Lin, Bin,Liu, Yongxiang
, p. 1312 - 1319 (2018/02/09)
A microwave-irradiated solvent-free pinacol rearrangement of hydrobenzoin substrates catalyzed by a combination of N-fluorobenzenesulfonimide and FeCl3·6H2O was developed. Its selectivity was first investigated by density functional theory (DFT) calculations. Then the functional group tolerance was examined by synthesizing a series of substrates designed based on the insight provided by the DFT calculations. The application of the methodology was demonstrated by the efficient one-pot synthesis of (±)-latifine and (±)-cherylline, both are 4-aryltetrahydroisoquinoline alkaloids isolated from Amaryllidacecae plants.
Air-Stable Blue Phosphorescent Tetradentate Platinum(II) Complexes as Strong Photo-Reductant
Li, Kai,Wan, Qingyun,Yang, Chen,Chang, Xiao-Yong,Low, Kam-Hung,Che, Chi-Ming
supporting information, p. 14129 - 14133 (2018/10/15)
Strong photo-reductants have applications in photo-redox organic synthesis involving reductive activation of C?X(halide) and C=O bonds. We report herein air-stable PtII complexes supported by tetradentate bis(phenolate-NHC) ligands having peripheral electron-donating N-carbazolyl groups. Photo-physical, electrochemical, and computational studies reveal that the presence of N-carbazolyl groups enhances the light absorption and redox reversibility because of its involvement into the frontier MOs in both ground and excited states, making the complexes robust strong photo-reductant with E([Pt]+/*) over ?2.6 V vs. Cp2Fe+/0. The one-electron reduced [Pt]? species are stronger reductants with EPC([Pt]0/?) up to ?3.1 V vs. Cp2Fe+/0. By virtue of the strong reducing nature of these species generated upon light excitation, they can be used in light-driven reductive coupling of carbonyl compounds and reductive debromination of a wide range of unactivated aryl bromides.
A Toolbox Approach to Construct Broadly Applicable Metal-Free Catalysts for Photoredox Chemistry: Deliberate Tuning of Redox Potentials and Importance of Halogens in Donor-Acceptor Cyanoarenes
Speckmeier, Elisabeth,Fischer, Tillmann G.,Zeitler, Kirsten
supporting information, p. 15353 - 15365 (2018/11/30)
The targeted choice of specific photocatalysts has been shown to play a critical role for the successful realization of challenging photoredox catalytic transformations. Herein, we demonstrate the successful implementation of a rational design strategy for a series of deliberate structural manipulations of cyanoarene-based, purely organic donor-acceptor photocatalysts, using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a starting point. Systematic modifications of both the donor substituents as well as the acceptors' molecular core allowed us to identify strongly oxidizing as well as strongly reducing catalysts (e.g., for an unprecedented detriflation of unactivated naphthol triflate), which additionally offer remarkably balanced redox potentials with predictable trends. Especially halogen arene core substitutions are instrumental for our targeted alterations of the catalysts' redox properties. Based on their preeminent electrochemical and photophysical characteristics, all novel, purely organic photoredox catalysts were evaluated in three challenging, mechanistically distinct classes of benchmark reactions (either requiring balanced, highly oxidizing or strongly reducing properties) to demonstrate their enormous potential as customizable photocatalysts, that outperform and complement prevailing typical best photocatalysts.
MeOH or H2O as efficient additive to switch the reactivity of allylSmBr towards carbonyl compounds
Li, Jianyong,Niu, Qingsheng,Li, Shanchan,Sun, Yuehao,Zhou, Qian,Lv, Xin,Wang, Xiaoxia
supporting information, p. 1250 - 1253 (2017/03/10)
A variety of carbonyl compounds were treated by allylSmBr (allylSmBr) with MeOH as the cosolvent to have further insights on the previously reported reductive coupling of aryl ketones mediated by Sm/alkyl halide/MeOH. The results demonstrate that the real reducing species in Sm/alkyl halide/MeOH system should be allylSmBr, and MeOH has elegantly switched the reactivity of allylSmBr from being nucleophilic to being good reductive coupling reagent. Besides, H2O was also found to be a useful additive to realize the pinacol coupling of aliphatic aldehydes and ketones promoted by allylSmBr.
Electrochemical pinacol coupling of aromatic carbonyl compounds in a [BMIM][BF4]-H2O mixture
Kronenwetter, Hannah,Husek, Jakub,Etz, Brian,Jones, Aaron,Manchanayakage, Renuka
supporting information, p. 1489 - 1495 (2014/03/21)
The electrochemical pinacol coupling reactions of aromatic carbonyl compounds were carried out using an 80% [BMIM][BF4]-H2O mixture as the electrolytic medium. The corresponding diols were obtained in good to excellent yields with moderate diastereoselectivity. The stereoselectivity can be explained using the strongly-bound ion-pairs formed between the imidazolium cation and the radical anions of the carbonyl compounds. The ionic liquid replaces both organic solvents and supporting electrolytes generally used in the electrosynthetic method. The electrolytic medium can be recycled and successfully reused at least in five consecutive reactions.
