Formation Of Secondary Amines Research Articles

ChemInform Abstract: Secondary Amine Formation from Reductive Amination of Carbonyl Compounds Promoted by Lewis Acid Using the InCl3/Et3SiH System.

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Secondary Amine Formation from Reductive Amination of Carbonyl Compounds Promoted by Lewis Acid Using the InCl3/Et3SiH System

A robust and reliable method has been developed for reductive amination of primary amines with various aldehydes and ketones using Zn(ClO(4))(2) x 6 H(2)O as a catalyst. [In-H] generated in situ via a combination of InCl(3) and Et(3)SiH is employed as an effective reducing system. A variety of secondary amines can be synthesized in a one-pot procedure in excellent yields.

Investigations into the mechanism of the liquid-phase hydrogenation of nitriles over Raney-Co catalysts

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.

The Effective Preparation of Secondary Amines Bearing a Vinylsilane Functionality via the reaction of Primary Amines with α-chlorine-substituted Allylsilanes Catalysed by CuCl

The reaction of α-chlorine-substituted allylsilanes with primary amines was promoted by CuCl to result in the selective formation of secondary amines bearing the vinylsilane functionality by a probable SN2′-allylation keeping the silyl group intact.

Aqueous-Mediated N-Alkylation of Amines.

Direct N-alkylation of primary amines to secondary/tertiary amines and of secondary amines to tertiary amines has been achieved in excellent yields by employing alkyl, benzylic and allylic halides in the presence of NaHCO3 in an aqueous medium at an elevated temperature. Amines of different stereoelectronic nature react with ease with different halides. The selective formation of secondary amines and the formation of three different substituted tertiary amines are some of

Aqueous‐Mediated N‐Alkylation of Amines

AbstractDirect N‐alkylation of primary amines to secondary/tertiary amines and of secondary amines to tertiary amines has been achieved in excellent yields by employing alkyl, benzylic and allylic halides in the presence of NaHCO3 in an aqueous medium at an elevated temperature. Amines of differentstereoelectronic nature react with ease with different halides. The selective formation of secondary amines and the formation of three different substituted tertiary amines are some of the interesting features of this methodology. Reaction in an aqueous medium, operationally convenient conditions, excellent yields and innocuous byproducts, and the absence of transition‐metal catalysts, expensive bases, solid supports and the formation of undesired quaternary ammonium salts makes this method a green chemical process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Palladium Catalysts on Alkaline‐Earth Supports for Racemization and Dynamic Kinetic Resolution of Benzylic Amines

Palladium catalysts on alkaline-earth supports were studied as new heterogeneous catalysts for racemization of chiral benzylic amines such as 1-phenylethylamine. Particularly 5 % Pd/BaSO(4) and 5 % Pd/CaCO(3) were able to selectively racemize amines, with minimal formation of secondary amines or hydrogenolysis to ethylbenzene. In contrast, these side reactions were pronounced on Pd/C. A reaction mechanism is proposed that is consistent with the reaction kinetics. The catalyst activity was found to depend on the number of available surface Pd atoms, determined by titration with CO. The selectivity crucially depends on the rate of condensation of the amine and the primary imine, which is highest on Pd/C. The racemization catalysts were combined in one pot with an immobilized lipase to perform dynamic kinetic resolution of chiral amines. High yields (up to 88 %) of essentially enantiopure amides were obtained in a single step. The chemo-enzymatic catalyst system proved to be stable and could be reused without losing the initial activity.

Thermal decomposition of bisphenol A-based polyetherurethanes blown with pentane: Part I—Thermal and pyrolytical studies

In this work thermal decomposition of ethoxylated 2,2-bis-(4-hydroxyphenyl)propane (BPA) and oxyalkylenated 2,6-toluyldiamine (TDA)-based rigid polyurethane (PU) foam, blown with pentane, is described. Thermogravimetry coupled with mass spectrometry (TG–MS) and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR) results of the evolution of volatile products during the degradation and gas chromatography coupled with mass spectrometry analysis of condensed products of PU foam pyrolysis (Py/GC–MS) are presented. Four temperature ranges of volatile products emission were detected under inert atmosphere—pentane used as blowing agent volatilizes in first range, the second one is dominated by dissociation reaction of urethane bonds by which first order amines, CO 2 and vinyl bonds, are formed, while complex reactions with formation of secondary amine and CO 2 occur in the third stage. Fourth stage is visible by further CO 2 evolution. Ethylene oxide and derivatives of dioxane, formed due to the presence of oxyalkylene chains, act as fuel during the burning of PU foam.

Synthesis of functionalized amine oligomers by free‐radical telomerization of methyl methacrylate with a peculiar telogen: 2‐Aminoethanethiol hydrochloride

AbstractThe Telomerization of methyl methacrylate with 2‐aminoethanethiol hydrochloride initiated by 2,2′‐azobisisobutyronitrile, was investigated in dimethylformamide (DMF). First, the peculiar behavior of 2‐aminoethanethiol was highlighted because it behaves as a peculiar transfer agent; this is because its transfer constant (CT) is weak compared with that of other thiols. The presence of the amine function greatly disturbs the free radical telomerization reaction. Telomerization was performed in the presence of hydrochloric acid (HCl) to protect the amine group. The transfer constant was strongly influenced by the acid and water concentration. This work emphasized that the nature of the solvent plays an important role in the determination of the transfer constant. Thus, the value of CT increased from 0.23 in DMF to 0.56 in the HCl/DMF mixture. The primary and secondary amines were recovered after the reaction. The functionality of the primary and secondary amines was measured by titration. The influence of the concentration of HCl on the resulting amine functionality was investigated. The acid presence prevents the formation of secondary amines, arising from Michael's reaction, on methyl methacrylate. Finally, these results were applied to the synthesis of amine‐functionalized telomers with molecular masses of 2000 to 15,000 g/mol. The amine function was correlated with the decrease of R0 ([telogen]/[monomer]). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5146–5160, 2004

Nitroxides scavenge myeloperoxidase-catalyzed thiyl radicals in model systems and in cells.

Nitroxide radicals possess important antioxidant activity in live tissues because of their ability to scavenge reactive radicals. Despite the fact that, in cells, damaging free radicals are primarily quenched by glutathione (GSH) with subsequent formation of harmful glutathionyl radical (GS(*)), interactions of nitroxide radicals with GS(*) and thiols have not been studied in detail. In addition, intracellular metabolic pathways leading to the formation of secondary amines from nitroxides are unknown. Here we report that GS(*) radicals react efficiently and irreversibly with nitroxides to produce secondary amines. We developed a sensitive method for the detection of GS(*) based on their specific interaction with Ac-Tempo, a nonfluorescent conjugate of fluorogenic acridine with paramagnetic nitroxide Tempo, and used it to characterize interactions between nitroxide and thiyl radicals generated through phenoxyl radical recycling by peroxidase. During reaction of Ac-Tempo with GS(*), Tempo EPR signals decayed and acridine fluorescence concurrently increased. DMPO and PBN, spin traps for GS(*), inhibited this interaction. Using combined HPLC and mass spectrometry, we determined that 90% of the Ac-Tempo was converted into fluorescent acridine (Ac)-piperidine; GSH was primarily oxidized into sulfonic acid. In myeloperoxidase-rich HL-60 cells, Ac-piperidine fluorescence was observed upon stimulation of GS(*) generation by H(2)O(2) and phenol. Development of fluorescence was prevented by preincubation of cells with the thiol-blocking reagent N-ethylmaleimide as well as with peroxidase inhibitiors. Furthermore, Ac-Tempo preserved intracellular GSH and protected cells from phenol/GS(*) toxicity, suggesting a new mechanism for the free-radical scavenging activity of nitroxides in live cells.

Ind(2)TiMe(2)]: a general catalyst for the intermolecular hydroamination of alkynes.

[Ind(2)TiMe(2)] (Ind=indenyl) is a highly active and general catalyst for the intermolecular hydroamination of alkynes. It catalyzes the reaction of primary aryl-, tert-alkyl-, sec-alkyl-, and n-alkylamines with internal and terminal alkynes. In the case of unsymmetrically substituted 1-phenyl-2-alkylalkynes, the reactions occur with modest to excellent regioselectivities, whereby formation of the anti-Markovnikov regioisomers is favored. While the major product of hydroamination reactions of terminal arylalkynes is always the anti-Markovnikov isomer, alkylalkynes react with arylamines to preferably give the Markovnikov products. To achieve reasonable rates for the addition of sterically less hindered n-alkyl- and benzylamines to alkynes, these amines must be added slowly to the reaction mixtures. This behavior is explained by the fact that the catalytic cycle proposed on the basis of an initial kinetic investigation includes the possibility that the rate of the reaction increases with decreasing concentration of the employed amine. Furthermore, no dimerization of the catalytically active imido complex is observed in the hydroamination of 1-phenylpropyne with 4-methylaniline in the presence of [Ind(2)TiMe(2)] as catalyst. In general, a combination of [Ind(2)TiMe(2)]-catalyzed hydroamination of alkynes with subsequent reduction leads to the formation of secondary amines with good to excellent yields. Particularly impressive is that [Ind(2)TiMe(2)] makes it possible for the first time to perform the reactions of n-alkyl- and benzylamines with 1-phenylpropyne in a highly regioselective fashion.

Synthesis of New Hydroxylated Monomers Based on Methacrylate, Dimethacrylate, and Tetramethacrylate Michael Adducts and Photopolymerization Kinetics of Bulk Cross-Linkers

A series of new hydroxylated monomers was synthesized from the Michael addition reaction between ethanolamine, diethylene glycol amine, triethylene glycol amine, tetradecylamine, and adamantanamine with 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM). Selective formation of secondary amine (mono adduct) or tertiary amine (bis adduct) products was obtained by controlling the stoichiometry of the reactants and reaction temperature. The Michael addition reactions were highly exothermic and carried out without the need of catalyst. The use of solvent, however, was required in some systems. The tetramethacrylate monomer was synthesized via the Michael addition reaction of 1,6-hexanediamine (HDA) to AHM. The photopolymerization kinetics of the synthesized monomers were investigated using differential scanning calorimeter. The rates of polymerization for the hydroxylated dimethacrylate systems were significantly higher than that of a typical dimethacrylate monomer (HDDMA) and approached that of the diacrylate...

Raman spectroscopic study of glutaraldehyde-stabilized collagen and pericardium tissue

For the first time, Raman spectroscopy has been employed to investigate formation of cross-links in collagen and porcine pericardium tissue upon glutaraldehyde (GA) treatment. GA treatment causes a very high fluorescence background, which overlaps Raman bands. It has been found that short fixation time, i.e. 2 h, reduces background radiation significantly, providing new possibilities for studying changes in molecular structure of collagen upon GA modification. The observed changes in position and intensity of Raman bands allowed us to recognize different types of GA–collagen interactions. Strong spectral evidence has been found for the peptide contribution to the formation of the GA–collagen cross-links and for the formation of secondary amines via Schiff base intermediates, and pyridinium-type cross-links. The results also revealed that different hydration levels and a more complex structure of intact tissue in comparison to collagen preparation strongly influence the formation of a GA cross-linking network, e.g. ether-type bond is preferred to form in a less hydrated collagen preparation. Our results have shown that GA treatment causes an increase in water content of pericardium tissue and collagen.

Solvent-mediated selective single and double ring-opening of N-tosyl-activated aziridines using benzylamine

An efficient methodology has been developed for the synthesis of a series of new diamine 2 and triamine ligands 3 for application in asymmetric catalysis via selective single or double ring-opening of tosylaziridines 1, which are derived from chiral pool amino acids. The selectivity of the ring-opening reaction is readily controlled by the solvent employed. Thus, in acetonitrile formation of secondary amines 2 occurs via a single ring-opening step, whilst in methanol the reactions proceed to give the tertiary amines 3 via the ring-opening of two aziridine molecules.

Asymmetric Synthesis of Homoallylic Amines and Functionalized Pyrrolidines via Direct Amino-Crotylation of In Situ Generated Imines

The asymmetric synthesis of functionalized homoallylic amines and silyl functionalized pyrrolidines through the Lewis acid promoted condensation of chiral ( E)-crotylsilanes with sulfonyl imines and in situ generated N-acyl imines is described. We had anticipated that this bond construction could be used in the asymmetric synthesis of the N-terminal amino acid subunit of the nikkomycins. Aryl sulfonyl imines condense with chiral silane reagents in the presence of BF 3·OEt 2 to form homoallylic arylsulfonyl amines with useful levels of syn selectivity. For cases involving aryl N-acyl imines we have learned that the temperature controls the course of the reaction. For instance, at temperatures of −78°C or below the major product is the pyrrolidine, while at higher temperatures (−30 to −20°C) the homoallylic amine is produced. For the cases studied, the [3+2]-annulation is limited to aryl imine derivatives, as alkyl- and branched- imines failed to produce the pyrrolidine derivatives: higher reaction temperatures promote the conversion of the annulation product to the homoallylic amines. In double stereodifferentiating reactions with in situ generated imines, good levels of selectivity were achieved in the formation of secondary amines bearing syn– anti and syn– syn stereochemical triads.

Process improvements from incident data

This paper discusses four different chemical processing accidents that resulted from plant mal-operations. Each incident was relatively minor yet provided valuable information about the stability and/or vulnerability of the process to upset conditions. The reaction classes involved were: Polyester polymerization Secondary amine formation followed by decomposition Oxidation of poly-alkylated aromatic hydrocarbon Base catalyzed oligomerization The paper describes the ‘after-the-fact’ data that was obtained by calorimetric hazards testing. We will discuss how the information was used, in each case to improve the process safety of the particular operation. We also describe an incident database that may be used by chemical companies to provide an on-going ranked and categorized record of accidents and incidents that have occurred. The value of the database information lies in the fact that the actual and potential severity of each accident is estimated from the data of the incident events. This information can be used to distinguish processes that may be responsible for the majority of the minor incidents from those processes where more severe, but infrequent, accidents occur. The information is also valuable in providing a focus with which to drive process safety improvement efforts.

Article

The preparation, characterization, properties, and reactivity of a novel quantum-confined CdS nanocluster containing a chemically active aniline surface are described, along with three general methods for the covalent attachment of a wide scope of molecular moieties to the cluster surface. The formation of facile covalent linkages via DCC mediated amidization, secondary amine formation, and thiourea condensation is discussed and, as the introduction of surface functionality is crucial for the eventual realization of molecular electronic devices fabricated from such nanoclusters, several derivatized nanoclusters bearing interesting chromophoric, fluorescent, electroactive, and chiroptical tethered species are described. All three derivatization techniques occur under very mild conditions that have been demonstrated not to disturb the integrity of the nanocluster core.Key words: quantum dot, nanocluster, semiconductor, surface-functionalized, nanostructured.

Surface functionalization of cadmium sulfide quantum-confined nanoclusters. 4. Formation and reactivity of an aniline surface quantum dot

The preparation, characterization, properties, and reactivity of a novel quantum-confined CdS nanocluster containing a chemically active aniline surface are described, along with three general methods for the covalent attachment of a wide scope of molecular moieties to the cluster surface. The formation of facile covalent linkages via DCC mediated amidization, secondary amine formation, and thiourea condensation is discussed and, as the introduction of surface functionality is crucial for the eventual realization of molecular electronic devices fabricated from such nanoclusters, several derivatized nanoclusters bearing interesting chromophoric, fluorescent, electroactive, and chiroptical tethered species are described. All three derivatization techniques occur under very mild conditions that have been demonstrated not to disturb the integrity of the nanocluster core.

Synthesis of fatty amines. Selectivity control in presence of multifunctional catalysts

Fatty and N-methyl (or ethyl) substituted amines used, for example, for the preparation of tensioactive agents are generally obtained from the reaction of fatty acids (or esters), ammonia, light alcohols and hydrogen or nitriles, light alcohols and hydrogen over copper or nickel catalysts. In these processes, the rate-limiting step is either the light alcohol (R'OH) dehydrogenation for the formation of RNR′ 2 or the secondary amine formation (R 2NH). In both cases the light alcohol and the by-product water have inhibiting effects under the rather severe experimental conditions. Over supported copper-chromite catalysts there exists a correlation between the selectivity to RNR′ 2 and the presence of a well dispersed copper chromite phase stabilized with alkaline-earth elements. However, over such catalysts the R 2NR′ amines cannot be obtained with high selectivity. In a second part of our study stimulated by the fact that environmental legislation will soon mandate replacements of copper-chromium catalysts with non-chromium catalysts, we investigated promoted nickel catalysts. In order to suppress the inhibiting effect of light alcohols, hexamethylene tetramine (HMTA) was used as methylating agent. Under these conditions, the nitrile is transformed either into dimethylalkylamine or into methyldialkylamine with a selectivity (or a yield) higher than 90%. Moreover, it was shown that HMTA was catalytically converted into monomethylamine (MMA), dimethylamine (DMA) and trimethylamine (TMA) during the reaction. These reagents specially MMA, DMA act as methylating agents of primary alkylamines (RNH 2) while the corresponding imines (CH 2=NH or CH 2=N-CH 3) would be the methylating species of the secondary alkylamine (R 2NH).

Mechanism study of deep-UV irradiated poly(methyl methacrylate)-azide resist system

Abstract The photochemical reactions of resist films consisting of poly(methyl methacrylate) (PMMA) and aromatic azide at high concentraton (25 wt.%) were studied. Both p-azidobenzoic acid (PABA) and 2,6-bis(4-azidylbenzylidene)-4-methyl cyclohexanone(2,6-bisazide) were used as the azide compounds. Chemical analysis carried out on the photoproducts of deep-UV irradiated PMMA-azide films revealed them to consist of unreacted azide compound, primary amine, azo dye, and PMMA with pendant secondary amines formed by nitrene insertion reactions. It is concluded that formation of secondary amines resulting from nitrene insertion to the PMMA chain were mainly responsible for both the dissolution rate retardation and the image reversal observed in the exposed PMMA-azide resist.