6344-72-5Relevant academic research and scientific papers
Homogeneous Nickel-Catalyzed Sustainable Synthesis of Quinoline and Quinoxaline under Aerobic Conditions
Bains, Amreen K.,Singh, Vikramjeet,Adhikari, Debashis
, p. 14971 - 14979 (2020/11/30)
Dehydrogenative coupling-based reactions have emerged as an efficient route toward the synthesis of a plethora of heterocyclic rings. Herein, we report an efficacious, nickel-catalyzed synthesis of two important heterocycles such as quinoline and quinoxaline. The catalyst is molecularly defined, is phosphine-free, and can operate at a mild reaction temperature of 80 °C. Both the heterocycles can be easily assembled via double dehydrogenative coupling, starting from 2-aminobenzyl alcohol/1-phenylethanol and diamine/diol, respectively, in a shorter span of reaction time. This environmentally benign synthetic protocol employing an inexpensive catalyst can rival many other transition-metal systems that have been developed for the fabrication of two putative heterocycles. Mechanistically, the dehydrogenation of secondary alcohol follows clean pseudo-first-order kinetics and exhibits a sizable kinetic isotope effect. Intriguingly, this catalyst provides an example of storing the trapped hydrogen in the ligand backbone, avoiding metal-hydride formation. Easy regeneration of the oxidized form of the catalyst under aerobic/O2 oxidation makes this protocol eco-friendly and easy to handle.
Nature of the Nucleophilic Oxygenation Reagent Is Key to Acid-Free Gold-Catalyzed Conversion of Terminal and Internal Alkynes to 1,2-Dicarbonyls
Dubovtsev, Alexey Yu.,Shcherbakov, Nikolay V.,Dar'in, Dmitry V.,Kukushkin, Vadim Yu.
, p. 745 - 757 (2020/02/04)
2,3-Dichloropyridine N-oxide, a novel oxygen transfer reagent, allows the conductance of the gold(I)-catalyzed oxidation of alkynes to 1,2-dicarbonyls in the absence of any acid additives and under mild conditions to furnish the target species, including those derivatized by highly acid-sensitive groups. The developed strategy is effective for a wide range of alkyne substrates such as terminal- and internal alkynes, ynamides, alkynyl ethers/thioethers, and even unsubstituted acetylene (40 examples; yields up to 99%). The oxidation was successfully integrated into the trapping of reactive dicarbonyls by one-pot heterocyclization and into the synthesis of six-membered azaheterocycles. This synthetic acid-free route was also successfully applied for the total synthesis of a natural 1,2-diketone.
Nickel/Photoredox-Catalyzed Methylation of (Hetero)aryl Chlorides Using Trimethyl Orthoformate as a Methyl Radical Source
Kariofillis, Stavros K.,Shields, Benjamin J.,Tekle-Smith, Makeda A.,Zacuto, Michael J.,Doyle, Abigail G.
supporting information, p. 7683 - 7689 (2020/04/22)
Methylation of organohalides represents a valuable transformation, but typically requires harsh reaction conditions or reagents. We report a radical approach for the methylation of (hetero)aryl chlorides using nickel/photoredox catalysis wherein trimethyl orthoformate, a common laboratory solvent, serves as a methyl source. This method permits methylation of (hetero)aryl chlorides and acyl chlorides at an early and late stage with broad functional group compatibility. Mechanistic investigations indicate that trimethyl orthoformate serves as a source of methyl radical via β-scission from a tertiary radical generated upon chlorine-mediated hydrogen atom transfer.
Iron-catalyzed Minisci acylation of N-heteroarenes with α-keto acids
Wang, Xiu-Zhi,Zeng, Cheng-Chu
supporting information, p. 1425 - 1430 (2019/02/01)
An efficient and mild protocol has been developed for the Minisci acylation reactions of nitrogen-containing heteroarenes with α-keto acids. Distinct from the conventional Minisci acylation conditions, the chemistry was performed using non-noble metal Fe(II), instead of expensive Ag(I) salt, as catalyst. A wide range of substrates, including aliphatic or aromatic α-keto acids, as well as various N-heteroarenes, proved to be compatible with the protocol. Scale-up experiment also demonstrates the practicality of the approach.
Potassium tert-Butoxide-Promoted Acceptorless Dehydrogenation of N-Heterocycles
Liu, Tingting,Wu, Kaikai,Wang, Liandi,Yu, Zhengkun
supporting information, p. 3958 - 3964 (2019/08/01)
Potassium tert-butoxide-promoted acceptorless dehydrogenation of N-heterocycles was efficiently realized for the generation of N-heteroarenes and hydrogen gas under transition-metal-free conditions. In the presence of KOtBu base, a variety of six- and five-membered N-heterocyclic compounds efficiently underwent acceptorless dehydrogenation to afford the corresponding N-heteroarenes and H2 gas in o-xylene at 140 °C. The present protocol provides a convenient route to aromatic nitrogen-containing compounds and H2 gas. (Figure presented.).
Rapid, efficient and eco-friendly procedure for the synthesis of quinoxalines under solvent-free conditions using sulfated polyborate as a recyclable catalyst
Indalkar, Krishna S,Khatri, Chetan K,Chaturbhuj, Ganesh U
, p. 141 - 148 (2017/02/23)
An efficient and inexpensive sulfated polyborate catalyst was applied for the rapid synthesis of quinoxaline derivatives from various substituted o-phenylenediamines and 1,2-diketones/α-hydroxy ketones using sulfated polyborate is described. The catalyst has the advantage of Lewis as well as Bronsted acidity and recyclability without significant loss in catalytic activity. The key advantages of the present method are high yields, short reaction times, solvent-free condition, easy workup, and ability to tolerate a variety of functional groups, which give economical as well as ecological rewards. [Figure not available: see fulltext.]
Ruthenium(II) η6-arene complexes containing a dinucleating ligand based on 1,8-naphthyridine
Tang, Wei-Hung,Liu, Yi-Hung,Peng, Shie-Ming,Liu, Shiuh-Tzung
, p. 94 - 100 (2015/01/08)
Ruthenium arene complexes, [(η6-p-cymene)2Ru2(L)Cl2](PF6)2 [3b, L = 2, 7-bis(di-2-pyridinyl)-1,8-naphthyridine] and [(η6-p-cymene)Ru(L′)Cl](PF6) [4, L′ = tri(2-pyridinyl)amine], were synthesized and characterized by spectroscopic and analytical techniques. The molecular structure of [(η6-p-cymene)2Ru2(L)Cl2]Cl2 (3a) was further determined by single-crystal X-ray analysis. The use of these ruthenium complexes as pre-catalysts for oxidative coupling of 1,2-diols/1,2-aminoalcohol with o-phenylenediamines leading to quinoxalines was investigated. Complex 3b appeared to be a good catalyst for this transformation.
A green synthesis of quinoxalines and 2,3-dihydropyrazines
Delpivo, Camilla,Micheletti, Gabriele,Boga, Carla
, p. 1546 - 1552 (2013/06/27)
Quinoxaline and dihydropyrazine derivatives were obtained in high yields by simple addition of 1,2-diamines and 1,2-dicarbonyl compounds in water. In some cases, the products spontaneously precipitated from the reaction mixture, making it possible to recover and reuse the mother liquor for further condensations. The very mild reaction conditions, the high yields of the products, and the absence of any catalyst make this methodology an efficient and green route to quinoxalines and dihydropyrazines. Georg Thieme Verlag Stuttgart New York.
Acceptorless dehydrogenation of nitrogen heterocycles with a versatile iridium catalyst
Wu, Jianjun,Talwar, Dinesh,Johnston, Steven,Yan, Ming,Xiao, Jianliang
supporting information, p. 6983 - 6987 (2013/07/26)
Gas up: A cyclometalated iridium complex is found to catalyze the dehydrogenation of various benzofused N-heterocycles, thus releasing H 2. Driven by as low as 0.1 mol % catalyst, the reaction affords quinolines, indoles, quinoxalines, isoquinolines, and β-carbolines in high yields. Copyright
Biomass into chemicals: One-pot two- and three-step synthesis of quinoxalines from biomass-derived glycols and 1,2-dinitrobenzene derivatives using supported gold nanoparticles as catalysts
Climent,Corma,Hernandez,Hungria,Iborra,Martinez-Silvestre
experimental part, p. 118 - 129 (2012/10/08)
An efficient and selective one-pot two-step method, for the synthesis of quinoxalines by oxidative coupling of vicinal diols with 1,2-phenylenediamine derivatives, has been developed by using gold nanoparticles supported on nanoparticulated ceria (Au/CeO2) or hydrotalcite (Au/HT) as catalysts and air as oxidant, in the absence of any homogeneous base. Reaction kinetics shows that the reaction controlling step is the oxidation of the diol to α-hydroxycarbonyl compound. Furthermore, a one-pot three-step synthesis of 2-methylquinoxaline starting from 1,2-dinitrobenzene and 1,2-propanediol has been successfully carried out with 98% conversion and 83% global yield to the final product.
