18240-50-1Relevant articles and documents
gem-dialkyl effect in the intramolecular Diels-Alder reaction of 2-furfuryl methyl fumarates: The reactive rotamer effect, enthalpic basis for acceleration, and evidence for a polar transition state
Jung, Michael E.,Gervay, Jacquelyn
, p. 224 - 232 (1991)
Investigation of the rates of cyclization of a series of substituted 2-furfuryl methyl fumarates 1a-h has allowed us to determine which of the two explanations for the gem-dialkyl effect is more important. Studies with compounds substituted with small-membered rings showed that the rate acceleration is due primarily to the reactive rotamer effect and not to angle compression ("Thorpe-lngold effect"). For example, the cyclobutyl-substituted compound 1d would experience a reactive rotamer effect similar to that of the dimethyl compound 1e and thus should cyclize relatively rapidly if this effect were dominant. However, due to the small ring, 1d would have a larger "internal" angle than other disubstituted derivatives and thus should cyclize even more slowly than the dihydrido compound 1a if the angle compression effect were dominant. Since the cyclobutyl-substituted compound 1d cyclizes in CD3CN at 25 °C 208 times faster than the dihydrido compound 1a, we have concluded that the reactive rotamer effect outweighs angle compression in determining the rate of cyclization in this system. The activation parameters for the cyclization of 1a-f in CD3CN have been calculated. These data show that the large rate acceleration seen in this system, namely the significant lowering of the ΔG?, is due almost entirely to a lowering of the enthalpy of activation (ΔH?) and not to a difference in the entropy of activation. For example, on going from the dihydrido 1a to the monomethyl compound 1b, the 1.3 kcal/mol decrease in the ΔG? is almost entirely due to the 1.4 kcal/mol decrease in the ΔH?. Likewise, comparison of the dihydrido and dimethyl cases shows that the ΔΔG? of 4.5 kcal/mol is due very largely to the 4.9 kcal/mol difference in the ΔH? with little contribution from the entropy of activation (ΔS?). In fact, the entropy of activation is more negative for the more substituted cases (1b vs 1a and 1e vs 1a or 1b) and would, therefore, retard the rate rather than accelerate it, if it were not for the enthalpy change (an isokinetic relationship). The rate enhancements due to the gem-dialkyl effect in this system are much higher than those generally seen in other systems (normally no larger than a factor of 10 for the dimethyl case vs the dihydrido one, but here a ratio of 2100). This discrepancy in rate effects is almost certainly due to the presence of an oxygen atom in the tether of our system next to the affected carbon compared to the all carbon tethers in the other cases. Finally, examination of the effect of solvents on this reaction reveals a strong acceleration of the cycloaddition in polar solvents, with the reaction being slowest in toluene, faster in acetonitrile, and faster again in DMSO. The solvent effect can be quite large in certain cases, with Arel being as large as 3200. The results for the monomethyl compound 1b in a wide variety of solvents indicate a better agreement with the dielectric constant of the solvent rather than other solvent polarity parameters, such as ET. This solvent effect is explained by the rotation of the most stable conformation of the starting material, the s-trans ester conformation 5, about the C-O bond to give the higher energy s-cis conformation 6, which can then cyclize via the transition state 7 to the observed products, the lactones 2. Since the s-cis conformation and the transition state derived from it have a net dipole due to the overlap of the dipoles of the ester, it is more polar than the starting material and thus would be expected to be stabilized by polar solvents. This is not the case for the intermolecular cycloaddition because the s-cis ester conformation is not required in the transition state. As additional evidence for this mechanistic rationale, the analogous tertiary amide 8, which would not have this more polar transition state (relative to the starting material), shows essentially no solvent effect in several solvents under similar conditions.
SYNTHESIS, STRUCTURES, AND REDOX PROPERTIES OF SOME NEW DITHIOCARBAMATES THAT INCLUDE A HETEROAROMATIC RING
Gol'dfarb, Ya. L.,Ostapenko, E. G.,Vinogradova, V. G.,Zverev, A. N.,Polyakov, A. V.,et. al.
, p. 740 - 747 (1987)
New Cu, Ni, Pb, Zn, Co, Fe, Mn, Sb, and Bi dithiocarbamates that include 2-thenyl and 2-furfuryl radicals were sythesized.The potentials of polarographic oxidation on a rotating platinum electrode were determined for them and for the previously synthesized N-substituted unsymmetrical dithiocarbamates of the same metals.The results of x-ray diffraction analysis of bis(di-2-thenyldithiocarbamato)nickel(2+) are presented and discussed.
Selective Synthesis of Furfurylamine by Reductive Amination of Furfural over Raney Cobalt
Zhou, Kuo,Chen, Bixian,Zhou, Xiaoting,Kang, Shimin,Xu, Yongjun,Wei, Jinjia
, p. 5562 - 5569 (2019)
Effect of metal nature on reductive amination was investigated with biomass-based furfural as a typical substrate. Among the tested heterogeneous metal catalysts, cobalt proved to be the most effective metal for the synthesis of the corresponding primary amine. Under a relatively mild reaction condition, 98.9 % yield of furfurylamine was obtained over Raney Co and it can be reused more than eight times without a significant decrease in the catalytic performance. By extensively studying the catalytic pathways and reaction mechanism, it is found that the selectivity to primary amine and secondary amine was governed by the relative rate of hydrogenolysis and hydrogenation of the Schiff base intermediate. The superiority of Raney Co in furfurylamine synthesis can be ascribed to its high efficiency on hydrogenolysis of the Schiff base intermediate and its low performance in the hydrogenation of the Schiff base, carbonyl group and furan ring. Furthermore, ammonia greatly promoted the catalytic hydrogenolysis of the Schiff base intermediate over Raney Co without clear deactivation of the metal active sites.
Direct Amination of Biomass-based Furfuryl Alcohol and 5-(Aminomethyl)-2-furanmethanol with NH3 over Hydrotalcite-derived Nickel Catalysts via the Hydrogen-borrowing Strategy
Zhou, Kuo,Xie, Ruihong,Xiao, Meiting,Guo, Darun,Cai, Zhuodi,Kang, Shimin,Xu, Yongjun,Wei, Jinjia
, p. 2074 - 2085 (2021)
A series of hydrotalcite-derived nickel catalysts were synthesized and employed for the direct amination of biomass-based furfuryl alcohol with NH3 via the hydrogen borrowing strategy. The effects of the Ni/Al molar ratio and calcination temperature of the NiAl hydrotalcite-like precursors on the performance of the NixAl-CT catalyst were investigated. The systematic characterization showed that the synergistic catalysis of the metal and acid-base sites was of vital importance for the amination of alcohols. In particular, the Ni2Al-600 catalyst with high amount of Ni0 sites (1.26 mmol g?1) and suitable density of acid-base sites (0.71 mmol g?1 and 1.10 mmol g?1, respectively) exhibited the best dehydrogenation capability and therefore excellent catalytic activity. An 84.1 % yield of furfurylamine with complete conversion of furfuryl alcohol was obtained under the reaction conditions of 180 °C and 0.4 MPa NH3 in 36 h. The presence of Ni3N in the spent catalyst, confirmed by XRD, TEM and XPS characterizations, was demonstrated to be responsible for the deactivation of the NixAl-CT catalyst. In addition, the Ni2Al-600 catalyst exhibited satisfactory performance toward another important biomass-related transformation of 5-(aminomethyl)-2-furanmethanol to 2,5-bis(aminomethyl)furan, with a yield of 70.5 %.
Ru/HZSM-5 as an efficient and recyclable catalyst for reductive amination of furfural to furfurylamine
Dong, Chenglong,Wang, Hongtao,Du, Haochen,Peng, Jiebang,Cai, Yang,Guo, Shuai,Zhang, Jianli,Samart, Chanatip,Ding, Mingyue
, (2020)
Furfurylamine converted from biomass-based platform molecules furfural was proven a significant intermediate in the synthesis of different valuable compounds. The combination of Ruthenium with HZSM-5 was acted as an excellent selective and reusable catalyst for the reduction amination of furfural with environmentally friendly ammonia and hydrogen. Incorporation of Ru species into HZSM-5 had a significant enhancement to the acid sites of Ru/HZSM-5. The Ru/HZSM-5(46) catalyst with optimized acid sites and interaction of the Ru-O-Al bond displayed an excellent catalytic performance, producing 76 % yield of furfurylamine at only 15 min, and could be recycled five times without loss of performance. Synergistic effect between RuO2 and metallic Ru in the Ru/HZSM-5 catalyst facilitated the reduction amination of furfural.
Selective catalysis for the reductive amination of furfural toward furfurylamine by graphene-co-shelled cobalt nanoparticles
Liu, Jianguo,Ma, Longlong,Zhong, Shurong,Zhuang, Xiuzheng
, p. 271 - 284 (2022/01/19)
Amines with functional groups are widely used in the manufacture of pharmaceuticals, agricultural chemicals, and polymers but most of them are still prepared through petrochemical routes. The sustainable production of amines from renewable resources, such as biomass, is thus necessary. For this reason, we developed an eco-friendly, simplified, and highly effective procedure for the preparation of a non-toxic heterogeneous catalyst based on earth-abundant metals, whose catalytic activity on the reductive amination of furfural or other derivatives (more than 24 examples) proved to be broadly available. More surprisingly, the cobalt-supported catalyst was found to be magnetically recoverable and reusable up to eight times with an excellent catalytic activity; on the other hand, the gram-scale tests catalyzed by the same catalyst exhibited the similar yield of the target products in comparison to its smaller scale, which was comparable to the commercial noble-based catalysts. Further results from a series of analytical technologies involving XRD, XPS, TEM/mapping, and in situ FTIR revealed that the structural features of the catalyst are closely in relation to its catalytic mechanisms. In simple terms, the outer graphitic shell is activated by the electronic interaction as well as the induced charge redistribution, enabling the easy substitution of the –NH2 moiety toward functionalized and structurally diverse molecules, even under very mild industrially viable and scalable conditions. Overall, this newly developed catalyst introduces the synthesis of amines from biomass-derived platforms with satisfactory selectivity and carbon balance, providing cost-effective and sustainable access to the wide applications of reductive amination.
Switching Selectivity in Copper-Catalyzed Transfer Hydrogenation of Nitriles to Primary Amine-Boranes and Secondary Amines under Mild Conditions
Song, Hao,Xiao, Yao,Zhang, Zhuohua,Xiong, Wanjin,Wang, Ren,Guo, Liangcheng,Zhou, Taigang
, p. 790 - 800 (2022/01/11)
A simple and efficient copper-catalyzed selective transfer hydrogenation of nitriles to primary amine-boranes and secondary amines with an oxazaborolidine-BH3 complex is reported. The selectivity control was achieved under mild conditions by switching the solvent and the copper catalysts. More than 30 primary amine-boranes and 40 secondary amines were synthesized via this strategy in high selectivity and yields of up to 95%. The strategy was applied to the synthesis of 15N labeled in 89% yield.
Comparative account of catalytic activity of Ru- and Ni-based nanocomposites towards reductive amination of biomass derived molecules
Bhanage, Bhalchandra M.,Gokhale, Tejas A.,Raut, Amol B.
, (2021/06/18)
This work includes an effective comparison of metallic ruthenium and nickel nanoparticles loaded on montmorillonite clay (MMT) for reductive amination reaction of biomass-derived molecules. It comprises an eco-friendly reaction using water as a solvent, utilizing molecular hydrogen and liquor ammonia (25% aq. solution) for the synthesis of primary amines from bio-derived aldehydes within 3–10 h of reaction time. Various parameters such as temperature, hydrogen pressure, substrate/ammonia concentration ratio, and reaction time were optimized while comparing the selectivity of primary amines for both catalysts. The applicability scope of these catalysts was explored with a library of aryl and heterocyclic aldehydes. The reductive amination of crude furfural extracted from biomass feedstock (rice husk) and pure xylose sugar was tested, showing yields in the range of 11–36%, to show the wider industrial scope of both nanocomposites. Gram scale conversion was also carried out to showcase the bulk scalability of the Ru/MMT catalyst.
Self-regulated catalysis for the selective synthesis of primary amines from carbonyl compounds
Fan, Xiaomeng,Gao, Jin,Gao, Mingxia,Jia, Xiuquan,Ma, Jiping,Xu, Jie
supporting information, p. 7115 - 7121 (2021/09/28)
Most current processes for the general synthesis of primary amines by reductive amination are performed with enormously excessive amounts of hazardous ammonia. It remains unclear how catalysts should be designed to regulate amination reaction dynamics at a low ammonia-to-substrate ratio for the quantitative synthesis of primary amines from the corresponding carbonyl compounds. Herein we show a facile control of the reaction selectivity in the layered boron nitride supported ruthenium catalyzed reductive amination reaction. Specifically, locating ruthenium to the edge surface of layered boron nitride leads to an increased hydrogenation activity owing to the enhanced interfacial electronic effects between ruthenium and the edge surface of boron nitride. This enables self-accelerated reductive amination reactions which quantitatively synthesize structurally diverse primary amines by reductive amination of carbonyl compounds with twofold ammonia. This journal is
Hydrosilylative reduction of primary amides to primary amines catalyzed by a terminal [Ni-OH] complex
Pandey, Pragati,Bera, Jitendra K.
supporting information, p. 9204 - 9207 (2021/09/20)
A terminal [Ni-OH] complex1, supported by triflamide-functionalized NHC ligands, catalyzes the hydrosilylative reduction of a range of primary amides into primary amines in good to excellent yields under base-free conditions with key functional group tolerance. Catalyst1is also effective for the reduction of a variety of tertiary and secondary amides. In contrast to literature reports, the reactivity of1towards amide reduction follows an inverse trend,i.e., 1° amide > 3° amide > 2° amide. The reaction does not follow a usual dehydration pathway.
