5325-97-3Relevant academic research and scientific papers
Intramolecular Cobalt-Mediated Cycloaddition of Linear Enediynes. A Useful Synthetic Entry into Cobalt-Protected Tricyclic Dienes and Their Synthetic Elaboration
Sternberg, Ethan D.,Vollhardt, K. Peter C.
, p. 1564 - 1573 (1984)
CpCo(CO)2 undergoes reaction with the linear α,δ,ω-enediynes 4, 10, 18, 22 and 25 to give the CpCo-complexed tricyclic dienes 5, 11, 19, 20, 23, 24, 26, and possibly 27.The free ligands may be obtained in good yield by oxidative demetalation.Treatment of the dienylsilane 12 with bromine gave the desilylated aromatic 13, whereas reaction with m-chloroperbenzoic acid furnished the dienol 14 and α-trimethylsilyl β,γ-enone 15.The latter rearranged to the desilylated α,β-enone 17 with acid.Some mechanistic discussion is presented concerned with the course of the cobalt-mediated cyclization reaction.Hydride abstraction from 11 resulted in the cation 28 which underwent unexpected nucleophilic addition to both ligands, in addition to deprotonation to benzene complex 32 and the free aromatic ligand 31.
Ligand-enabled and magnesium-activated hydrogenation with earth-abundant cobalt catalysts
Han, Bo,Jiao, Hongmei,Ma, Haojie,Wang, Jijiang,Zhang, Miaomiao,Zhang, Yuqi
, p. 39934 - 39939 (2021/12/31)
Replacing expensive noble metals like Pt, Pd, Ir, Ru, and Rh with inexpensive earth-abundant metals like cobalt (Co) is attracting wider research interest in catalysis. Cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. Herein, we describe a hydrogenation method for polycyclic aromatic hydrocarbons (PAHs) and olefins with a magnesium-activated earth-abundant Co catalyst. When diketimine was used as a ligand, simple and inexpensive metal salts of CoBr2in combination with magnesium showed high catalytic activity in the site-selective hydrogenation of challenging PAHs under mild conditions. Co-catalyzed hydrogenation enabled the reduction of two side aromatics of PAHs. A wide range of PAHs can be hydrogenated in a site-selective manner, which provides a cost-effective, clean, and selective strategy to prepare partially reduced polycyclic hydrocarbon motifs that are otherwise difficult to prepare by common methods. The use of well-defined diketimine-ligated Co complexes as precatalysts for selective hydrogenation of PAHs and olefins is also demonstrated.
Aromatic compound hydrogenation and hydrodeoxygenation method and application thereof
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Paragraph 0094-0095; 0106-0113, (2021/05/29)
The invention belongs to the technical field of medicines, and discloses an aromatic compound hydrogenation and hydrodeoxygenation method under mild conditions and application of the method in hydrogenation and hydrodeoxygenation reactions of the aromatic compounds and related mixtures. Specifically, the method comprises the following steps: contacting the aromatic compound or a mixture containing the aromatic compound with a catalyst and hydrogen with proper pressure in a solvent under a proper temperature condition, and reacting the hydrogen, the solvent and the aromatic compound under the action of the catalyst to obtain a corresponding hydrogenation product or/and a hydrodeoxygenation product without an oxygen-containing substituent group. The invention also discloses specific implementation conditions of the method and an aromatic compound structure type applicable to the method. The hydrogenation and hydrodeoxygenation reaction method used in the invention has the advantages of mild reaction conditions, high hydrodeoxygenation efficiency, wide substrate applicability, convenient post-treatment, and good laboratory and industrial application prospects.
Catalyzed transfer hydrogenation by 2-propanol for highly selective PAHs reduction
Philippov,Chibiryaev,Martyanov
, p. 15 - 22 (2020/07/15)
Catalytic hydrogenation of mono-, di- and trinuclear aromatic compounds has been studied under hydrogen transfer conditions at 150 °C and 82 °C in 2-PrOH as a hydrogen donor and with Raney nickel as a catalyst. In contrast to conjugated or condensed aromatic rings, isolated ones demonstrated low reactivity in transfer hydrogenation (TH) that can be used to increase the hydrogenation selectivity of the reaction. So, naphthalene and biphenyl are partially hydrogenated into tetralin and cyclohexylbenzene, respectively, with excellent conversion (≥ 96 %) and selectivity (≥ 98 %) for 5–6 h at 82 °C. Increasing the reaction temperature to 150 °C results expectedly in the hydrogenation of second aromatic ring, which occurs slowly enough. Only 8 % of decaline and 42 % of dicyclohexyl, correspondingly, were obtained after 5 h at 150 °C. At the same time, TH of trinuclear anthracene and phenanthrene at 150 °C resulted in the formation of deeper hydrogenated octahydro-anthracenes and -phenanthrenes, respectively.
Metallic Barium: A Versatile and Efficient Hydrogenation Catalyst
Stegner, Philipp,F?rber, Christian,Zenneck, Ulrich,Knüpfer, Christian,Eyselein, Jonathan,Wiesinger, Michael,Harder, Sjoerd
supporting information, p. 4252 - 4258 (2020/12/22)
Ba metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non-conjugated) mono-, di- and tri-substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba0, that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba0 and BaH2 are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH2) confirm that the presence of metallic Ba has an accelerating effect.
Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings
Eyselein, Jonathan,F?rber, Christian,Grams, Samuel,Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Martin, Johannes,Thum, Katharina,Wiesinger, Michael
supporting information, p. 9102 - 9112 (2020/03/30)
Two series of bulky alkaline earth (Ae) metal amide complexes have been prepared: Ae[N(TRIP)2]2 (1-Ae) and Ae[N(TRIP)(DIPP)]2 (2-Ae) (Ae=Mg, Ca, Sr, Ba; TRIP=SiiPr3, DIPP=2,6-diisopropylphenyl). While monomeric 1-Ca was already known, the new complexes have been structurally characterized. Monomers 1-Ae are highly linear while the monomers 2-Ae are slightly bent. The bulkier amide complexes 1-Ae are by far the most active catalysts in alkene hydrogenation with activities increasing from Mg to Ba. Catalyst 1-Ba can reduce internal alkenes like cyclohexene or 3-hexene and highly challenging substrates like 1-Me-cyclohexene or tetraphenylethylene. It is also active in arene hydrogenation reducing anthracene and naphthalene (even when substituted with an alkyl) as well as biphenyl. Benzene could be reduced to cyclohexane but full conversion was not reached. The first step in catalytic hydrogenation is formation of an (amide)AeH species, which can form larger aggregates. Increasing the bulk of the amide ligand decreases aggregate size but it is unclear what the true catalyst(s) is (are). DFT calculations suggest that amide bulk also has a noticeable influence on the thermodynamics for formation of the (amide)AeH species. Complex 1-Ba is currently the most powerful Ae metal hydrogenation catalyst. Due to tremendously increased activities in comparison to those of previously reported catalysts, the substrate scope in hydrogenation catalysis could be extended to challenging multi-substituted unactivated alkenes and even to arenes among which benzene.
Chromium- and Cobalt-Catalyzed, Regiocontrolled Hydrogenation of Polycyclic Aromatic Hydrocarbons: A Combined Experimental and Theoretical Study
Han, Bo,Ma, Pengchen,Cong, Xuefeng,Chen, Hui,Zeng, Xiaoming
supporting information, p. 9018 - 9026 (2019/06/13)
Polycyclic aromatic hydrocarbons are difficult substrates for hydrogenation because of the thermodynamic stability caused by aromaticity. We report here the first chromium- and cobalt-catalyzed, regiocontrolled hydrogenation of polycyclic aromatic hydrocarbons at ambient temperature. These reactions were promoted by low-cost chromium or cobalt salts combined with diimino/carbene ligand and methylmagnesium bromide and are characterized by high regioselectivity and expanded substrate scope that includes tetracene, tetraphene, pentacene, and perylene, which have rarely been reduced. The approach provides a cost-effective catalytic protocol for hydrogenation, is scalable, and can be utilized in the synthesis of tetrabromo- and carboxyl-substituted motifs through functionalization of the hydrogenation product. The systematic theoretical mechanistic modelings suggest that low-valent Cr and Co monohydride species, most likely from zerovalent transition metals, are capable of mediating these hydrogenations of fused PAHs.
Method for selectively catalyzing and hydrogenating polycyclic aromatic hydrocarbon based on cobalt salt
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Paragraph 0037; 0038-0041; 0062; 0063-0066; 0117-0121, (2017/10/22)
The invention discloses a method for selectively catalyzing and hydrogenating polycyclic aromatic hydrocarbon based on cobalt salt. According to the method, cobalt salt and methyl magnesium bromide are taken as catalysts, N-heterocyclic carbine or 2,2'-dipyridyl is taken as a ligand, tetrahydrofuran is taken as a solvent, polycyclic aromatic hydrocarbon is stirred to react under mild conditions in an H2 atmosphere, so as to obtain a hydrogenated product. Based on regulation and control of N-heterocyclic carbine or 2,2'-dipyridyl and synergistic catalysis of cobalt salt and methyl magnesium bromide, the high-selectivity hydrogenation of polycyclic aromatic hydrocarbon is realized under mild conditions. The method has the advantages of low cost, mild reaction conditions, high selectivity, wide substrate application range and the like and can be used for hydrogenating different substituted anthracene derivative and other polycyclic aromatic hydrocarbon substrates.
Synthesis of tetraline derivatives through depolymerization of polyethers with aromatic compounds using a heterogeneous titanium-exchanged montmorillonite catalyst
Maeno, Zen,Torii, Hiroyuki,Yamada, Shota,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro
, p. 89231 - 89233 (2016/10/03)
A novel depolymerization of poly(tetramethylene glycol) (PTMG) with benzene to tetralin using titanium-exchanged montmorillonite (Ti4+-mont) as a solid acid catalyst is described. This catalyst is applicable to depolymerization of PTMG with some aromatic compounds. This is the first demonstration of the potential use of PTMG as a C4 synthon for organic synthesis.
One-pot synthesis of tetralin derivatives from 3-benzoylpropionic acids: Indium-catalyzed hydrosilylation of ketones and carboxylic acids and intramolecular cyclization
Sakai, Norio,Kobayashi, Taichi,Ogiwara, Yohei
, p. 1503 - 1505 (2015/11/24)
This reducing system was composed of a small amount (1 mol%) of In(OAc)3, Me2PhSiH, and I2 that effectively catalyzed the hydrosilylation of two different carbonyl groups, a ketone and a carboxylic acid found in 3-benzoylpropionic acids, followed by a subsequent intramolecular cyclization that led to the one-pot preparation of tetralin derivatives.
