918-02-5Relevant academic research and scientific papers
Diverse catalytic reactivity of a dearomatized PN3P?-nickel hydride pincer complex towards CO2 reduction
Li, Huaifeng,Gon?alves, Théo P.,Zhao, Qianyi,Gong, Dirong,Lai, Zhiping,Wang, Zhixiang,Zheng, Junrong,Huang, Kuo-Wei
supporting information, p. 11395 - 11398 (2018/10/20)
A dearomatized PN3P?-nickel hydride complex has been prepared using an oxidative addition process. The first nickel-catalyzed hydrosilylation of CO2 to methanol has been achieved, with unprecedented turnover numbers. Selective methylation and formylation of amines with CO2 were demonstrated by such a PN3P?-nickel hydride complex, highlighting its versatile functions in CO2 reduction.
Ruthenium-Catalyzed Methylation of Amines with Paraformaldehyde in Water under Mild Conditions
van der Waals, Dominic,Heim, Leo. E.,Gedig, Christian,Herbrik, Fabian,Vallazza, Simona,Prechtl, Martin H. G.
, p. 2343 - 2347 (2016/10/24)
Methylated amines are highly important for a variety of pharmaceutical and agrochemical applications. Existing routes for their formation result in the production of large amounts of waste or require high reaction temperatures, both of which impact the ecological and economical footprint of the methodologies. Herein, we report the ruthenium-catalyzed reductive methylation of a range of aliphatic amines, using paraformaldehyde as both substrate and hydrogen source, in combination with water. This reaction proceeds under mild aqueous reaction conditions. Additionally the use of a secondary phase for catalyst retention and recycling has been investigated with promising results.
Amination of aliphatic alcohols catalyzed by CuO-NiO/γ-Al 2O3
Huang, Jia-Min,Qian, Chao,Feng, Lie,Chen, Yun-Bin,Chen, Xin-Zhi
, p. 1187 - 1190 (2013/08/23)
The amination of aliphatic alcohols in the gas-solid phase was investigated in a fixed-bed reactor in the presence of CuO-NiO/γ-Al2O 3 as the catalyst. This catalytic system was successfully applied for both the N-methylation of aliphatic amines and N-alkylation of piperidine with primary or secondary alcohols. N-Alkylation of piperidine with low-carbon alcohols resulted in high conversions and selectivities, and the conversion of piperidine and the selectivities toward the desired products declined gradually with the increase of the carbon number of aliphatic alcohols. The influence of varied conditions on the N-cyclohexylation of piperidine was also evaluated, including liquid hourly space velocity (LHSV), temperature and the catalyst; especially the catalyst had the greatest impact. Finally, the test of the catalyst's stability was performed.
Reductive methylation of primary and secondary amines and amino acids by aqueous formaldehyde and zinc
da Silva, Renato A.,Estevam, Idália H.S.,Bieber, Lothar W.
, p. 7680 - 7682 (2008/03/30)
Amines can be methylated when treated with formaldehyde and zinc in aqueous medium. Selective mono- or dimethylation can be achieved by proper choice of pH, stoichiometry and reaction time. This method can also be applied for amino acids.
Phenyl chloro(thionoformate): A new dealkylating agent of tertiary amines
Milan, David S.,Prager, Rolf H.
, p. 841 - 849 (2007/10/03)
Phenyl chloro(thionoformate) reacts rapidly with unhindered tertiary aliphatic amines at 20° to give a thiocarbamate and an alkyl chloride. Dialkylcyclohexylamines react surprisingly rapidly to form predominantly cyclohexene. The thiocarbamates are converted into the secondary amine salt by treatment with dimethyl sulfate, followed by hydrolysis with water. Rates of reaction and alkyl group cleavage selectivity in amines were found to be superior or comparable to those previously reported with chloroformates.
Intramolecular motions in a series of crystalline benzylammonium bromides and dibenzylamines studied by CP/MAS NMR
Riddell, Frank G.,Rogerson, Martin
, p. 493 - 504 (2007/10/03)
A series of 15 compounds including ammonium bromides containing one or two benzyl groups with H, methyl, isopropyl, tert-butyl and tert-amyl substituents and dibenzylamihe with N-isopropyl-, N-tert-butyl- and N-tert-amyl substituents have been synthesised and studied by CP/MAS NMR. The results of dynamic NMR studies on the solids suggest that there is a dramatically wide range of molecular motions occurring in this simple series of compounds: A combination of 2D CPEXSY, dynamic line shape analyses and T1ρ measurements reveals the considerable extent of intramolecular group motions including rotations of methyl, tert-butyl, tert-amyl and phenyl groups. Rates of rotation and activation parameters for these molecular motions are derived where appropriate. In the case of benzyl-tert-butylammonium bromide, where two independent molecules of the compound exist in the asymmetric unit it is shown that the independent processes of tert-butyl rotation in the two molecules have vastly different activation energies that differ by ca. 16 kJ mol-1. The extent of the motions observed suggests that commonly held prejudices about the rigidity of molecules in crystalline solids need revising.
A flash photolysis study of the oxidation of aliphatic amines by phosphate radical
Subramanian, P,Rajaram, J,Ramarkrishnan, V,Kuriacose, J C
, p. 913 - 919 (2007/10/02)
Rate constants for the reaction of the phosphate radical (PO42-) with various aliphatic amines have been measured by flash kinetic spectrophotometry.Phosphate radical can react with aliphatic amines by hydrogen atom abstraction or electron transfer, the general reactivity order being tertiary secondary primary.For tertiary amines, a good correlation has been obtained when the logarithm of rate constants are plotted against the oxidation peak potentials of the amines, providing clear evidence for an electron transfer mechanism.In the case of tertiary amines, electron transfer from the nitrogen takes place.The identification of aminium cation radicals in the case of cyclic tertiary amines like, 1,4-diazabicyclooctane (DABCO) and 1,3,6,8-tetraazatricyclododecane (TATCD) provides additional proof for electron transfer.Primary and secondary amines get oxidized mainly by hydrogen atom abstraction as shown by the poor correlation with Taft substituent constants, but electron transfer cannot be completely ruled out.In the case of t-butylamine, electron transfer takes place and t-butylalcohol has been identified as the end product.
Ion-Dipole Complexes in the Unimolecular Reactions of Isolated Organic Ions. Effect of N-Methylation on Olefin and Amine Loss from Protonated Aliphatic Amines
Bowen, Richard D.,Harrison, Alex G.,Reiner, Eric J.
, p. 1009 - 1014 (2007/10/02)
The slow unimolecular fragmentation reactions os 18 gaseous protonated aliphatic amines of general formula R1NH(1+)R2R3 (R1=Prn, Pri, Bun, Bui, Bus, or But; R2,R3=H,CH3) are reported and discussed.Two decomposition routes are observed for a metastable ions R1NH(1+)R2R3.The first involves elimination of a neutral amine, R2R3NH, and formation of a carbocation, R1(1+), via a mechanism involving an incipient cation bound to the developing amine by an ion-dipole attraction.Rearrangement of the cation, to give thermodynamically more stable isomers, is feasible in these ion-dipole complexes.Further reorganization of the complexes leads to a species in which an incipient olefin 1-H> and an amine 2R3NH> are co-ordinated to a common proton.Dissociation of these proton-bound complexes, with retention of the proton by the developing amine, results in olefin loss, which is the secondreaction undergone by metastable ions R1NH(1+)R2R3.The relative abundance of amine expulsion is greater for protonated amines containing a primary alkyl group, R1, than is the case for isomeric ions containing secondary or tertiary alkyl groups.Progressive methylation of the nitrogen atom decreases the relative abundance of amine loss from R1NH(1+)R2R3, regardless of the nature of the principal alkyl group.These two trends are explained in terms of the energetics of the intermediates and products involved in the decomposition of the protonated amines.
