Formation Of Tertiary Amines Research Articles

Selective hydrogenation of amides using bimetallic Ru/Re and Rh/Re catalysts

Heterogeneous Ru/Re and Rh/Re catalysts, formed in situ from Ru 3(CO) 12/Re 2(CO) 10 and Rh 6(CO) 16/Re 2(CO) 10 respectively, are effective for the liquid phase hydrogenation of cyclohexanecarboxamide (CyCONH 2) to CyCH 2NH 2 in up to 95% selectivity without the requirement for ammonia to inhibit secondary and tertiary amine formation. Good amide conversions are noted within the reaction condition regimes 50–100 bar H 2 and ⩾150 (Rh) – 160 °C (Ru). Variations in Ru:Re and Rh:Re composition result in only minor changes in product selectivity with no evidence of catalyst deactivation at higher levels of Re. In situ HP-FTIR spectroscopy has shown that catalyst genesis occurs via decomposition of the metal carbonyl precursors. Ex situ characterization, using XRD, XPS and EDX-STEM, has provided evidence for the active components of these catalysts containing bimetallic Ru/Re and Rh/Re nanoclusters, the surfaces of which become significantly oxidized after use in amide reduction. Potential mechanistic pathways for amide hydrogenation are discussed, including initial dehydration to nitrile, a pathway potentially specifically accessible to primary amides, and evidence for often postulated imine intermediates.

Ruthenium-Catalyzed Tertiary Amine Formation from Nitroarenes and Alcohols

A highly selective ruthenium-catalyzed C-N bond formation was developed by using the hydrogen-borrowing strategy. Various tertiary amines were obtained efficiently from nitroarenes and primary alcohols. The reaction tolerates a wide range of functionalities. A tentative mechanism was proposed for this direct amination reaction of alcohols with nitroarenes.

Accelerating effects of N‐aryl‐N′,N′‐dialkyl ureas on epoxy‐dicyandiamide curing system

AbstractThis report focuses on epoxy‐dicyandiamide (DICY) curing system accelerated by N‐aryl‐N′,N′‐dialkyl urea, aiming at clarifying the accelerating mechanism and the relationship between accelerating effect and molecular structure of the accelerators. Nine N‐aryl‐N′,N′‐dialkyl ureas were synthesized and investigated with measurements of differential scanning calorimetry, thermo gravimetric/differential thermal analysis and NMR spectroscopy. The results revealed that the ureas released the corresponding secondary amines by the thermal dissociation in the presence of epoxide, which led to the formation of tertiary amines that catalyze the addition reaction of DICY to epoxide. Moreover, a tendency that the ureas able to release more compact amines exhibited higher acceleration effects was discovered. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Three‐Component Coupling Reactions of Thioformamides with Organolithium and a Grignard Reagents Leading to Formation of Tertiary Amines and a Thiolating Agent.

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Three-Component Coupling Reactions of Thioformamides with Organolithium and Grignard Reagents

The use of N,N-dialkylthioform­amides for the generation of tertiary amines via a novel three-component coupling reaction with ­organolithium and Grignard reagents is demonstrated. Thus, a variety of valuable tertiary amines, including the biologically significant diarylmethyl­piperazines, were synthesized. It is noteworthy that the order of addition of the organolithium and Grignard reagents is vital to the success of the reaction. Remarkably, an excess of the organolithium reagent, which is first added to the N,N-dialkyl­thioformamide, does not interfere with the outcome of the reaction. In addition to the formation of tertiary amines a new thiolating agent, supposedly LiSMgBr, is formed during the coupling reaction.

Three-Component Coupling Reactions of Thioformamides with Organolithium and Grignard Reagents Leading to Formation of Tertiary Amines and a Thiolating Agent

A highly efficient three-component coupling reaction between thioformamides and organolithium and Grignard reagents was developed. The generality of the process has been demonstrated by using various combinations of reactants and reagents. Information about the mechanism of the reaction has come from 1H and 13C NMR spectroscopic detection of the key intermediate. The LiS group in the intermediates generated by addition of the organolithium reagents to the thioformamides serves as a leaving group. The solid byproduct formed in these reactions, formulated as [LiSMgBr], can be used as a thiolating agent to transform acid chlorides into thioic acids and thioic acid anhydrides.

Zinc-Promoted Aminomethylation of Organic Halides

This work presents an extremely simple and surprisingly general synthetic method for aminomethylation of organic halides, i.e. formation of tertiary amines with one ‘additional’ CH2 group. The described method is an ingenious one-pot combination of a Barbier-type reaction and acid-catalyzed imine formation. The mechanism differs from the usual formation of organozinc species followed by a nucleophilic attack. Copper iodide was found to catalyze the process, whereas a radical quencher such as BHT is an inhibitor. The reaction starts with the formation of a radical derived from the alkyl halide, which reacts immediately with a highly electrophilic immonium cation. Probably, the copper salts participate in this step. This is leading to a cation-radical, which is reduced by Zn to form the final amine. The radical pathway was proved by using the ‘radical clock’ 6-iodo-1-hexene, which gave mostly the cyclization product.

An efficient and operationally convenient general synthesis of tertiary amines by direct alkylation of secondary amines with alkyl halides in the presence of Huenig’s base

A general method for the direct formation of tertiary amines via direct N-alkylation of secondary amines by alkyl halides in acetonitrile in the presence of Hunig’s base is reported. In contrast to methods previously reported in the literature, this procedure is highly functional group tolerant and employs operationally convenient conditions in the absence of transition metal catalysts or solid supports and without formation of the undesired quaternary ammonium salt.

Mechanistic Studies of Photobase Generation from Ammonium Tetraorganyl Borate Salts1

The photochemistry and photophysics of N,N,N-tributyl-N-acetonaphthone ammonium borate (1) and N,N,N-tributyl-N-acetobenzo[b]furan ammonium borate (2) have been investigated by steady-state spectroscopy, laser flash photolysis, and product analysis. Reaction of excited precursors leads to formation of tertiary amines by carbon−nitrogen bond cleavage. Laser flash photolysis and product analysis confirm homolytic carbon−nitrogen bond scission and the formation of respective acetyl radicals which, in acetonitrile, dimerize to form coupled products. In all cases, photodissociation occurs with such a short lifetime that it could not be measured by nanosecond flash photolysis. The quantum yield of disappearance was found to be higher for salts of the triphenylbutyl borate anion than for those of the tetraphenyl borate anion. A proposed mechanism involves electron transfer from borate to the excited acceptors as the primary photochemical step. The rate constants for excited-state quenching correlate with the fre...

Cis/Trans Reactivity: Epoxy-Amine Systems.

The reactivities of cis and trans isomers of 1,2-diaminocyclohexane (1,2-DCH)/epoxy resin were studied separately. We found that the primary amine hydrogen disappears in both isomers at a similar rate when they react with an epoxy resin. However, the formation of tertiary amines differs considerably. The reactivity of the second amine hydrogen for the trans isomer is greater than that for the cis isomer, and this difference is observed as the reaction proceeds. The main reason for the slower disappearance of the cis secondary amine is steric hindrance and this fact is observed in the preexponential factors, glass transition temperatures (Tg), and ratio of rate constants of secondary to primary amine (R). The reaction was followed by Fourier transform infrared spectroscopy in the near-infrared range. The values of Tg were obtained by differential scanning calorimetry.

Preparation of secondary amines by reductive amination with metallic magnesium

A novel and efficient method for the preparation of secondary amines by reductive amination of carbonyl compounds with primary amines has been developed. The reduction, effected with metallic magnesium in methanol, utilizing triethylamine–acetic acid as a buffer, gave pure secondary amines, mostly in good yields (65–80%). No formation of tertiary amines or alcohols was observed. Use of ammonium acetate as an amino component gave primary amines in modest yields (ca. 50%), together with variable amounts of secondary amines. Enamines failed to undergo reduction. The method is inexpensive, relatively rapid, operationally simple and suitable for large-scale preparations. In addition, a simple method for separation of primary amines from secondary ones has been developed.

An efficient synthesis of the benzhydrylpiperazine delta opioid agonist (+)-BW373U86

A diastereoselective version of Katritzky's method for tertiary amine formation provides an efficient route to the highly selective, non-peptidal, delta opioid agonist (+)-4-[(αR)-α-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-hydroxybenzyl]-N,N-diethylbenzamide [(+)-BW373U86], 1.

Alternative group V sources for growth of GaAs and AlGaAs by MOMBE (CBE)

We have investigated the use of phenylarsine (PhAsH 2) and trisdimethylaminoarsenic (DMAAs) as potential replacements for AsH 3 during growth by metalorganic molecular beam epitaxy (MOMBE), alternatively known as chemical beam epitaxy (CBE). PhAsH 2 was found to decompose rather inefficiently on the surface at a growth temperature of 525°C. However, GaAs and AlGaAs growth rates up to ∼ 95 Å/min could still be obtained at this temperature without incurring any degradation in morphology. The hydrogen generated by the decomposition of the PhAsH 2 did not appear to getter carbon from the surface as both GaAs and AlGaAs grown from PhAsH 2 contained ten times more carbon than layers grown under the same flux of AsH 3. By contrast, DMAAs was found to decompose readily on the wafer surface allowing growth rates up to 220 Å/min and growth temperatures as low as 375°C. Furthermore, DMAAs was found to getter carbon more efficiently than cracked AsH 3, probably as a result of tertiary amine formation at the wafer surface. As a result, comparable carbon backgrounds were obtained at 525°C from either TEG or TMG. By using these sources in tandem, it appears that AsH 3 may no longer be required for growth of GaAs or AlGaAs by MOMBE. In addition, these sources allow new flexibility for selective growth as well. The stability of PhAsH 2 allows for selective deposition of pAlGaAs even at temperatures as low as 525°C. While the same effect is not observed for GaAs growth from TEG at these temperatures, it is possible through the use of DMAAs to deposit high purity GaAs selectivity from TMG since the DMAAs getters the carbon without inducing deposition on the mask. Thus the use of PhAsH 2 and DMAAs will allow selective deposition of device structures such as Pnp HBTs at their optimum growth temperature of ∼ 525°C.

Determination of tertiary amines in non-aqueous solvents in the presence of primary and secondary amines

In the formation of tertiary amines in the mechanism of the reaction of 1:3 BADGE/m-XDA (bisphenol A diglycidyl ether/m-xylylenediamine) equivalent ratio epoxy-amine formulations, we have used FAB mass spectrometry to confirm the different mechanisms of epoxy-amine reactions described by Shechter et al. (3) and have adapted a reaction to give a fluorescent adduct with tertiary amines for their colorimetric determination in the presence of primary and secondary amines, reporting several advantages over the previous method.

Kinetics and Mechanism of Hydrolysis of Labile Quaternary Ammonium Derivatives of Tertiary Amines

The kinetics and mechanism of hydrolysis of N-(4-hydroxy-3,5-dimethylbenzyl)pyridinium bromide and similar quaternary derivatives of niacinamide, N,N-dimethylaniline, and trimethylamine were investigated. pH-Rate profiles at 25 degrees for formation of tertiary amine and 4-hydroxymethyl-2,6-dimethylphenol indicated that the zwitterionic quaternary phenoxide was the reactive species in alkaline solution. The apparent rate of hydrolysis was strongly inhibited by addition of small amounts of product tertiary amine, which is consistent with the presence of an intermediate in the reaction pathway. A mechanism was proposed for the hydrolysis and methanolysis of these compounds involving the reversible formation of the quinone methide, 4-methylene,-2,6-dimethyl-2,5-cyclohexadien-1-one, followed by a trapping reaction with solvent or nucleophiles. Replacement of the phenolic hydrogen with methyl or acetyl groups greatly stabilized the molecule which is in agreement with the proposed mechanism. For the ester, the rate of amine release was limited by specific base catalyzed hydrolysis of the ester group. Compounds of this type may be useful in prodrug design for tertiary amines. The possibility of quinone methine intermediates in the degradation of structurally similar drugs, such as epinephrine, was discussed.

NMR analysis of the hardening of epoxy resins by piperidine

The hardening of an epoxy resin and a model compound (phenylglycidyl ether) by piperidine with additions of CoCl 2, CuCl 2 and piperidine trisulphide was investigated by using high resolution NMR. With the reaction of the model compound as an example it is shown that in the course of hardening there are stages of tertiary amine formation and quaternization of the amine. The addition of piperidine leads to a marked change in the reaction mechanism, the process becoming autocatalytic.

Secondary and tertiary amines derived from pelargonaldehyde and methyl azelaaldehydate

AbstractReductive alkylation of ammonia with pelargonaldehyde or with methyl azelaaldehydate over Raney nickel catalyst produced dinonylamine or bis(8‐carbomethoxyoctyl)amine in good yields. Tertiary amine formation was minimized by the use of two immiscible solvents. When 10% palladium on charcoal was used in place of the nickel catalyst, trinonylamine and tris(8‐carbomethoxyoctyl)amine were formed in good yield in the absence of solvents.