The palladium catalysed hydrogenation of multi-functional aromatic nitriles (original) (raw)
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… 2011: Engineering a …, 2011
The hydrogenolysis of nitriles (R-C≡N) to the corresponding methyl compound (R-CH 3 ) is relatively uncommon. Generally, forcing conditions Watanabe, 1959, Weigert and or the use of a complicated or difficult to handle catalyst are required, while under mild conditions R-CH 3 generally occurs as a by-product of the hydrogenation of nitriles.(Bakker et al., 2010) However, we have performed the facile hydrogenolysis of not only various nitriles, but also of imines and amines over Pd/C using straightforward and relatively mild conditions (80 o C, 1 atm H 2 , in EtOH).
EFFECTIVE CATALYSTS FOR THE SELECTIVE RESTORATION OF AROMATIC MONO- AND DINITRO COMPOUNDS
News of the Academy of Sciences of the Republic of Kazakhstan of the National Academy of Sciences of the Republic of Kazakhstan, Series Chemistry and Technology, 2020
This article discusses the issues of catalytic reduction of aromatic nitro compounds to obtain valuable intermediate and final products-aromatic amines. The most important method for producing amines from nitro compounds is catalytic reduction with hydrogen on catalysts. The article describes in detail the choice of catalysts for hydrogenation of nitro compounds at atmospheric and high hydrogen pressure. Studies of hydrogenation reactions of aromatic nitro compounds on nickel, copper and iron catalysts are discussed. Hydrogenation of aromatic nitro compounds on catalysts based on palladium, platinum, and rhodium deposited on various carriers, including nanodiamonds, is considered. Catalysts based on supported palladium catalysts with copper additives showed high selectivity in the hydrogenation of nitro groups in nitro compounds with functional groups; and with the addition of platinum and rhodium, during the reduction of both nitro groups and the aromatic ring in nitrobenzene. In the works on the use of nanodiamonds, it was found that catalysts based on platinum and palladium nanoparticles of 4-5 nm in size, fixed on nanodiamonds, were highly active in liquid-phase hydrogenation reactions of nitro compounds under mild conditions. The data described by the authors on theoretical issues and practical problems of catalytic hydrogenation of aromatic nitro compounds are very relevant. The article is based on the analysis of domestic and foreign literature and may be useful to specialists in the field of catalysis.
Highly Diastereoselective Hydrogenation of Imines by a Bimetallic Pd−Cu Heterogeneous Catalyst
Organic Process Research & Development, 2010
An efficient and practical heterogeneous bimetallic Pd-Cu/C catalyst was identified as an alternative to Raney nickel for the highly diastereoselective hydrogenation of imines prepared from prochiral ketones and r-phenylethylamines. Chiral amines were obtained with diastereomeric excess (de) up to 94% using Pd-Cu/ C, while conventional Pd-C catalysts afforded only 72% de. Optimization showed that a robust process required a palladium/ copper ratio of 4:1. Evidence for the influence of catalyst pretreatment which may change the structure of the catalyst and/or metal oxidation states on the selectivity of the reaction is discussed. The bimetallic catalyst system provided consistent results on scale and performed reliably on a variety of substrates.
Simultaneous Hydrogenation of Multiring Aromatic Compounds over NiMo Catalyst
Industrial & Engineering Chemistry Research, 2008
Hydrogenation of six model feeds containing three-, two-, and one-ring aromatic compounds was investigated to gain insights into the aromatic hydrogenation reaction chemistry over a commercial NiMo catalyst under practical reaction conditions. The hydrogenation reactivity of the aromatic compounds followed the following order: phenanthrene ∼ two-ring aromatics . one-ring aromatic. Comparison with previous studies revealed that the relative reactivity of the aromatic compounds is strongly influenced by the nature of the catalyst. Multiple-component feed studies showed that phenanthrene and naphthalene strongly inhibited the tetralin hydrogenation rate; however, naphthalene and tetralin had no appreciable effect on phenanthrene conversion. Langmuir-Hinshelwood-type rate equations were used to describe the reaction kinetics with physically meaningful and well-identified parameter values. The inhibition was attributed to competitive adsorption and was described in the kinetic model by adsorption terms that were obtained from the multicomponent feed experiments.
Applied Catalysis A General, 2015
ABSTRACT The liquid-phase hydrogenation of cinnamonitrile to selectively obtain the unsaturated primary amine (cinnamylamine) was studied at 383 K and 13 bar on Ni, Co, Ru and Cu metals supported on a commercial silica. Ni/SiO2 and Co/SiO2 were the most active catalysts for cinnamonitrile conversion but formed only small amounts of cinnamylamine. In contrast, Cu/SiO2 and Ru/SiO2 presented low activity for cinna-monitrile hydrogenation but formed selectively cinnamylamine in the liquid phase; nevertheless, on both samples the carbon balance was only about 40%. In an attempt of promoting the rate and yield to cinnamy-lamine, additional catalytic runs were carried out at higher temperatures and H2 pressures on a highly dispersed Cu(11%)/SiO2 catalyst prepared by the chemisorption-hydrolysis method. Results showed that when cinnamonitrile hydrogenation was performed at 403 K and 40 bar on Cu(11%)/SiO2 , the yield to cin-namylamine was 74% giving as by-product only the unsaturated secondary amine (dicinnamylamine).
Journal of Catalysis, 2008
The co-hydrogenation of acetonitrile and butyronitrile over Raney-Co was investigated in order to obtain insight into the mechanism underlying the formation of secondary amines. Acetonitrile was reduced much faster to the corresponding primary amine due to stronger adsorption on the catalyst surface. In parallel, dialkylimines were formed and subsequently converted to secondary amines. It is suggested that the dialkylimines are formed by reaction of partially hydrogenated intermediate species on the cobalt surface with amines. In this respect, n-butylamine was found to react much faster than ethylamine. The stronger inductive effect of the butyl chain is thought to facilitate nucleophilic attack of the amine at the α-C-atom of the surface species. By comparing the C 2 and C 4 balance for dialkylimines and dialkylamines, it was found that direct hydrogenation of the dialkylimine cannot be the only way of dialkylamine formation. Instead, it is suggested that alkyl group transfer occurs by reaction of a monoalkylamine with a dialkylimine and cross-transfer between two dialkylimines.
Chemical Physics Letters, 2021
The mechanism of the transition metal iron complex [(iPr-PNP)Fe(H)Br(CO)] catalyzed reaction of selective hydrogenation of nitriles to secondary imines has been investigated with the M06-2X function. The results indicate that the reaction involves two basic processes: (i) A catalyzed p-bromobenzonitrile to benzaldimine and primary amine transformation; (ii) condensation of benzaldimine with a primary amine to afford secondary imine. The calculated barrier of transition metal-catalyzed condensation reaction of benzaldimine with a primary amine, 30.6 kcal/mol, indicates that the condensation reaction is feasible under experiment conditions. The theoretical results provide a deeper understanding of the mechanism and fully explain the experimental facts.
Chinese Journal of Catalysis, 2019
ABSTRACT The liquid-phase hydrogenation of butyronitrile to saturated amines was studied on sili-ca-supported Ni catalysts prepared by either incipient-wetness impregnation (Ni/SiO2-I) or ammonia (Ni/SiO2-A) methods. A Ni/SiO2-Al2O3-I sample was also used. Ni/SiO2-I was a non-acidic catalyst containing large Ni 0 particles of low interaction with the support, while Ni/SiO2-A was an acidic catalyst due to the presence of Ni 2+ species in Ni phyllosilicates of low reducibility. Ni/SiO2-I formed essentially butylamine (80%), and dibutylamine as the only byproduct. In contrast, Ni/SiO2-A yielded a mixture of dibutylamine (49%) and tributylamine (45%), being the formation of butyla-mine almost completely suppressed. The selective formation of secondary and tertiary amines on Ni/SiO2-A was explained by considering that butylamine is not release to the liquid phase during the reaction because it is strongly adsorbed on surface acid sites contiguous to Ni 0 atoms, thereby favoring the butylimine/butylamine condensation to higher amines between adsorbed species.