A Palladium-Catalyzed Multicascade Reaction: Facile Low-Temperature Hydrogenolysis of Activated Nitriles and Related Functional Groups (original) (raw)
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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).
Mechanistic and reaction engineering aspects of nitrile hydrogenation
2007
Liquid phase hydrogenation of nitriles is an important method for the production of primary amines, which find a variety of applications as intermediates in chemical and pharmaceutical industry. Raney-Co or supported Cobalt catalysts are frequently used due to the relatively high selectivity to primary amines. However, selectivities in excess of 95% can only be achieved, when ammonia is used as solvent. Thereby, thermodynamic control of the reaction is achieved as condensation reactions, where ammonia is released, are suppressed. However, liquid ammonia is difficult to handle and it is highly interesting to avoid, or at least to minimise, the addition of ammonia. This requires kinetic control of the reaction by optimizing catalyst properties and process conditions.
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.
Journal of the American Chemical Society, 1995
The ruthenium(II)-catalyzed reaction of nitriles with carbonyl compounds proceeds highly efficiently under neutral and mild conditions to give a&unsaturated nitriles. Under similar reaction conditions, nitriles react with olefins bearing electron-withdrawing groups to give the corresponding Michael adducts. The efficiency of the reaction is illustrated by the selective additions to a,p-unsaturated aldehydes and acetylenes bearing electron-withdrawing groups, which are difficult to perform using conventional bases. Chemoselective aldol and Michael reactions of nitriles can be performed in the presence of other active methylene compounds. Tandem Michael and Michaelaldol condensations of nitriles 30 can be performed with high diastereoselectivity. These reactions can be rationalized by assuming oxidative addition of rutheniuin(0) to the a-C-H bond of nitriles and subsequent insertions to carbonyl compounds or olefins. As the key intermediates and active catalysts hydrido(N-bonded enolato)ruthenium(II) complexes, ~~~-RuH(NCCHCO~R)(NCCH~CO~R)(PP~~)~ (R = Me (41a), Et (41b), n-Bu (41c)) have been isolated upon treatment of RuH2(PPh3)4 (3) or R u H ( C~H~) ( P P~~)~( P P~~C~~) (4) with alkyl cyanoacetates. Kinetic study of the catalytic aldol reaction of ethyl cyanoacetate with benzaldehyde indicates that the rate-determining step is the reaction of enolato complex 41 with aldehydes.
Applied Catalysis A: General 445– 446, 69–75, 2012
ABSTRACT The selective liquid-phase hydrogenation of butyronitrile to n-butylamine was studied in a batch reactor on Co(9.8%)/SiO2, Ni(10.5%)/SiO2, Cu(9.2%)/SiO2, Pt(0.27%)/SiO2, Pd(0.33%)/SiO2, and Ru(1.8%)/SiO2 catalysts. At 373 K and 13 bar (H2), the initial butyronitrile conversion rate (r0 BN, mmol/h g) followed the order Ni > Co > Pt > Ru > Cu > Pd. Cu/SiO2 and Pd/SiO2 did not form n-butylamine and rapidly deactivated during the progress of the reaction. Pt/SiO2 produced mainly dibutylamine and only minor amounts of n-butylamine and tributylamine. In contrast, Ru/SiO2 formed preponderantly n-butylamine but also produced significant amounts of dibutylamine and butylidene–butylamine, an intermediate in the formation pathway of the secondary amine. The highest yield to n-butylamine was obtained on Ni/SiO2 (84%). Co/SiO2 was initially highly selective to n-butylamine but with the progress of the reaction the butylamine concentration in the reaction mixture diminished because it partially reacted with the solvent (ethanol) to form N-ethylbutylamine. In an attempt to reduce the formation of byproducts, Ni/SiO2 and Co/SiO2 catalysts were tested at lower temperatures and higher H2 pressures. Butyronitrile was selectively converted to n-butylamine on Co/SiO2 at 343 K and 25 bar, yielding 97% of n-butylamine, similarly to the highest yields reported on Raney Co catalysts.
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).
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.