6948-01-2Relevant academic research and scientific papers
Oxidation Under Reductive Conditions: From Benzylic Ethers to Acetals with Perfect Atom-Economy by Titanocene(III) Catalysis
Funk, Pierre,Richrath, Ruben B.,Bohle, Fabian,Grimme, Stefan,Gans?uer, Andreas
, p. 5482 - 5488 (2021/02/03)
Described here is a titanocene-catalyzed reaction for the synthesis of acetals and hemiaminals from benzylic ethers and benzylic amines, respectively, with pendant epoxides. The reaction proceeds by catalysis in single-electron steps. The oxidative addition comprises an epoxide opening. An H-atom transfer, to generate a benzylic radical, serves as a radical translocation step, and an organometallic oxygen rebound as a reductive elimination. The reaction mechanism was studied by high-level dispersion corrected hybrid functional DFT with implicit solvation. The low-energy conformational space was searched by the efficient CREST program. The stereoselectivity was deduced from the lowest lying benzylic radical structures and their conformations are controlled by hyperconjugative interactions and steric interactions between the titanocene catalyst and the aryl groups of the substrate. An interesting mechanistic aspect is that the oxidation of the benzylic center occurs under reducing conditions.
ZIF-67 Derived Co/NC Nanoparticles Enable Catalytic Leuckart-type Reductive Amination of Bio-based Carbonyls to N-Formyl Compounds
Li, Chuanhui,Meng, Ye,Yang, Song,Li, Hu
, p. 5166 - 5177 (2021/10/25)
It is of great significance to develop non-precious metal catalysts with excellent catalytic activity, stability, and acid resistance for biomass valorization. Herein, catalytic amination of biomass carbonyl compounds was achieved via a Leuckart-type reaction over Co nanoparticles (NPs) embedded N-doped carbon catalyst, which was prepared by thermolysis of ZIF-67 precursor at different temperatures in the N2 atmosphere. The Co/NC-800 catalyst exhibited excellent catalytic activity and recyclability in furfural reductive amination to mono-substituted formamide, which was attributed to the synergistic catalytic action of Co NPs and nitrogen base sites of the catalyst. The reductive amination mechanisms were elucidated by theoretical calculations, and showed that the initial formation of C?N bond was derived from the condensation of furfural and formamide, followed by dehydration to form C=N double bond, which was then reduced by hydrogen species Co?H? and NH+. The developed catalytic system was applicable to different carbonyls for the synthesis of corresponding N-formyl compounds with up to 99 % yield.
Facile N-Formylation of Amines on Magnetic Fe3O4?CuO Nanocomposites
Datta Khanal, Hari,Mishra, Kanchan,Rok Lee, Yong
, p. 4477 - 4484 (2021/08/30)
A facile, eco-friendly, efficient, and recyclable heterogeneous catalyst is synthesized by immobilizing copper impregnated on mesoporous magnetic nanoparticles. The surface chemistry analysis of Fe3O4?CuO nanocomposites (NCs) by XRD and XPS demonstrates the synergistic effect between Fe3O4 and CuO nanoparticles, providing mass-transfer channels for the catalytic reaction. TEM images clearly indicate the impregnation of CuO onto mesoporous Fe3O4. This hydrothermally synthesized eco-friendly and highly efficient Fe3O4?CuO NCs are applied as a magnetically retrievable heterogeneous catalyst for the N-formylation of wide range of aliphatic, aromatic, polyaromatic and heteroaromatic amines using formic acid as a formylating agent at room temperature. The catalytic activity of the NCs for N-formylation is attributable to the synergistic effect between Fe3O4 and CuO nanoparticles. The N-formylated product is further employed for the synthesis of biologically active quinolone moieties.
Preparation and catalytic evaluation of a palladium catalyst deposited over modified clinoptilolite (Pd&at;MCP) for chemoselective N-formylation and N-acylation of amines
Amirsoleimani, Mina,Khalilzadeh, Mohammad A.,Zareyee, Daryoush
, (2020/08/22)
Novel palladium nanoparticles stabilized by clinoptilolite as a natural inexpensive zeolite prepared and used for N-formylation and N-acylation of amines at room temperature at environmentally benign reaction conditions in good to excellent yields. Pd (II) was immobilized on the surface of clinoptilolite via facile multi-step amine functionalization to obtain a sustainable, recoverable, and highly active nano-catalyst. The structural and morphological characterizations of the catalyst carried out using XRD, FT-IR, BET and TEM techniques. Moreover, the catalyst is easily recovered using simple filtration and reused for 7 consecutive runs without any loss in activity.
Catalyst freeN-formylation of aromatic and aliphatic amines exploiting reductive formylation of CO2using NaBH4
Kumar, Arun,Kumar, Yashwant,Mahajan, Dinesh,Sharma, Nidhi,Sharma, Pankaj
, p. 25777 - 25787 (2021/08/05)
Herein, we report a sustainable approach forN-formylation of aromatic as well as aliphatic amines using sodium borohydride and carbon dioxide gas. The developed approach is catalyst free, and does not need pressure or a specialized reaction assembly. The reductive formylation of CO2with sodium borohydride generates formoxy borohydride speciesin situ, as confirmed by1H and11B NMR spectroscopy. Thein situformation of formoxy borohydride species is prominent in formamide based solvents and is critical for the success of theN-formylation reactions. The formoxy borohydride is also found to promote transamidation reactions as a competitive pathway along with reductive functionalization of CO2with amine leading toN-formylation of amines.
Concentration-dependent circularly polarized luminescence of chiral cyclometalated platinum(II) complexes for electroluminescence
Guo, Song,Han, Jianmei,Liu, Shujuan,Lu, Hu,Tao, Peng,Xu, Yanan,Zhang, Xinwen,Zhao, Qiang,Zheng, Xiaokang
, (2020/03/30)
Circularly polarized organic light-emitting diodes (CP-OLEDs) have been attracting increasing attention due to the direct generation of CP light, and they show the improved image contrast and luminous efficiency in OLEDs displays. In this work, a pair of chiral Pt(II) complexes with methylbenzylisocyanide and 1,3-bis(2-pyridyl)benzene as a tridentate N∧C∧N ligand were synthesized. Both of them exhibited bright green emission in dilute acetonitrile solution, while strong orange emission in high concentration of acetonitrile solution. However, when the complexes were doped into polymethyl methacrylate, the green emission originated from intrinsic single molecule can be changed to the red emission from excimer by adjusting the doping ratios. More importantly, the amplification of CPL signal can be achieved compared with the solution state. Furthermore, the monochrome devices were fabricated by utilizing these two enantiomers as emitters.
UiO-66 as an efficient catalyst for N-formylation of amines with CO2 and dimethylamine borane as a reducing agent
Phatake, Vishal V.,Mishra, Ashish A.,Bhanage, Bhalchandra M.
supporting information, (2019/12/11)
The most effective way to make the best use of CO2, is the reductive formylation of amines, as formamides have many applications in industry. A new protocol has been developed for reductive N-formylation of amines with CO2 as a C1 carbon source and DMAB (Dimethylamine borane) as a reducing agent in the presence of Zr-containing metal–organic framework (MOF) as an efficient, heterogeneous recyclable catalyst. We used UiO-66 and UiO-66-NH2 as catalysts for N-formylation of amines and observed that both the catalyst performs equally. Therefore, we continued our studies with UiO-66 as a catalyst. The UiO-66 MOF shows good catalytic activity and affording the desired formamides in good to excellent yield. This catalytic system is very efficient for several amines including primary and secondary aliphatic cyclic and aromatic amines. Moreover, the prepared catalyst was recycled up to four recycled without a considerable decrease in catalytic activity.
Tetracoordinate borates as catalysts for reductive formylation of amines with carbon dioxide
Du, Chen-Xia,Huang, Zijun,Jiang, Xiaolin,Li, Yuehui,Makha, Mohamed,Wang, Fang,Zhao, Dongmei
supporting information, p. 5317 - 5324 (2020/09/17)
We report sodium trihydroxyaryl borates as the first robust tetracoordinate organoboron catalysts for reductive functionalization of CO2. These catalysts, easily synthesized from condensing boronic acids with metal hydroxides, activate main group element-hydrogen (E-H) bonds efficiently. In contrast to BX3 type boranes, boronic acids and metal-BAr4 salts, under transition metal-free conditions, sodium trihydroxyaryl borates exhibit high reactivity of reductive N-formylation toward a variety of amines (106 examples), including those with functional groups such as ester, olefin, hydroxyl, cyano, nitro, halogen, MeS-, ether groups, etc. The over-performance to catalyze formylation of challenging pyridyl amines affords a promising alternative method to the use of traditional formylation reagents. Mechanistic investigation supports electrostatic interactions as the key for Si/B-H activation, enabling alkali metal borates as versatile catalysts for hydroborylation, hydrosilylation, and reductive formylation/methylation of CO2.
Copper-Catalyzed Formylation of Amines by using Methanol as the C1 Source
Pichardo, Manuel Carmona,Tavakoli, Ghazal,Armstrong, Jessica E.,Wilczek, Tobias,Thomas, Bradley E.,Prechtl, Martin H. G.
, p. 882 - 887 (2020/02/11)
Cu/TEMPO catalyst systems are known for the selective transformation of alcohols to aldehydes, as well as for the simultaneous coupling of alcohols and amines to imines under oxidative conditions. In this study, such a Cu/TEMPO catalyst system is found to catalyze the N-formylation of a variety of amines by initial oxidative activation of methanol as the carbonyl source via formaldehyde and formation of N,O-hemiacetals and oxidation of the latter under very mild conditions. A vast range of amines, including aromatic and aliphatic, primary and secondary, and linear and cyclic amines are formylated under these conditions with good to excellent yields. Moreover, paraformaldehyde can be used instead of methanol for the N-formylation.
Bifunctional Pincer Catalysts for Chemoselective Transfer Hydrogenation and Related Reactions
Cohen, Shirel,Bilyachenko, Alexey N.,Gelman, Dmitri
, p. 3203 - 3209 (2019/02/09)
A comparative study on the chemoselective transfer hydrogenation of nitroarenes to anilines and related processes using FA as the hydrogen source is described; these processes are catalyzed by a series of pincer catalysts equipped with different functional groups in the secondary coordination sphere. Some new (4 and 5) as well as previously reported (1–3) catalysts belonging to the family of bifunctional PC(sp3)P pincer complexes were employed in this study The reported compounds exhibited remarkably different catalytic activity behavior, depending on the nature of the functional groups. Transfer hydrogenation of nitrobenzene with FA as a hydrogen source was probed using iridium complexes 3 or 4 as a catalyst. Under the same conditions, the analogous palladium complex was found to be useful for the selective amidation of aniline with light carboxylic acids.
