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Ruthenium-catalyzed selective imine synthesis from ..

The reaction is enabled by visible light photoredox initiated hole catalysis and the Brønsted acid ...

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An Atom Economic Acid Catalyzed Synthetic Method …

The reaction follows the regular mechanism of acid catalyzed condensation reactions. The CF3 moiety has a very strong electron withdrawing character, and coupled with the carbonyl oxygen’s electron withdrawing nature, the carbonyl C carries a strong partial positive charge that is significantly greater than that of a ketone without α-CF3 group. This enhanced δ+ charge, in fact, activate the first step in the mechanism, namely the nucleophilic attack on the C providing the highlighted intermediate. However, the subsequent protonation and water elimination of the key intermediate is not favored as the strong electron withdrawing effect of CF3 destabilizes the carbocationic intermediate (). As a result, the water elimination is the rate-determining step of the condensation reaction in the case of trifluoromethyl ketones.

7/23/2014 · Acid and base-catalyzed hydrolysis of amides ..

France, Scott P.; Hussain, Shahed; Hill, Andrew M.; Hepworth, Lorna J.; Howard, Roger M.; Mulholland, Keith R.; Flitsch, Sabine L.; Turner, Nicholas J. “One-Pot Cascade Synthesis of Mono- and Disubstituted Piperidines and Pyrrolidines using Carboxylic Acid Reductase (CAR), ω-Transaminase (ω-TA), and Imine Reductase (IRED) Biocatalysts”. ACS Catalysis (2016), 6(6), 3753-3759.

Acid Catalyzed Hydrolysis of a Cyclic Imine - Duration: ..

A new solid acid/superacid catalyzed microwave assisted synthesis of trifluoromethyl-imines is described. Various α,α,α-trifluoromethylketones react readily with primary amines to produce the corresponding imines. Two different strategies have been employed; one is the application of microwave irradiation coupled with solvent-free solid acid catalysis. The other method, for highly deactivated substrates includes the use of a pressure vessel at 175 °C temperature, with solid superacid catalysis. Using the solid acid K-10 montmorillonite or the superacidic perfluorinated resinsulfonic acid Nafion-H, a wide variety of trifluoromethylated imines have been synthesized using the above methods. The products have been isolated in good to excellent yields and high selectivities. This new environmentally friendly synthetic methodology provides significantly higher yields than traditional methods during relatively short reaction times for the preparation of the target compounds.

The PPNCo(CO)4 and BF3·Et2O catalyzed carbonylation of simple and functionalized epoxides in DME gives the corresponding β-lactones regioselectively in good to high yields. The carbonylation occurred selectively at the unsubstituted C−O bond of the epoxide ring, and this reaction tolerates various functional groups such as alkenyl, halide, hydroxy, and alkyl ether.

Acid-catalyzed ester hydrolysis (video) | Khan Academy

Herein, we describe a novel, environmentally benign approach for the synthesis of a wide variety of α,α,α-trifluoromethyl-imines. The combination of microwave irradiation and solid acid/superacid catalysis provides high yields while reasonably decreasing the reaction time and also minimizing the formation of undesirable byproducts. The major advantages of this method are short reaction times, high yields and selectivities and ease of work-up and isolation of products.

Beside the catalyst, the use of microwave irradiation and high temperature reaction in a pressure tube vessel were the most significant changes implemented. The microwave assisted reactions have been carried out under solvent-free conditions. The reactants and the catalyst were stirred in ether for 10 min, and then the solvent was removed providing a dry mixture of catalyst with reactants evenly distributed on its surface. This mixture was placed into the microwave cavity and irradiated for a specific time at constant temperature. It was observed that a traditional reaction at 175 °C using Nafion-H as catalyst resulted in only 5% improvement in yield, however, its use significantly reduced reaction times. The Nafion-H catalyzed microwave assisted reaction showed promise, unfortunately, the catalyst formed a dark melt and completely lost activity. Using the thermally stable K-10 as catalysts, the reaction gave nearly quantitative yield (95%) in very short time of irradiation (25 min). It is worth noting that both K-10 and Nafion-H are strong acids; however, the density of the acid centers is relatively low. Depending on the accessibility of the acid center to individual substrates, the amount of available acid centers varies between 1–5 mmol/kg (based on ion-exchange capacities) [, , ]. It means, for instance, that the 0.5 g K-10 used had about 5–25·10−4 mmol acid centers compare to 1–1.5 mmol reactants. As such, these materials, although used in relatively large amount are still considered as catalysts. Based on the results obtained under optimized reaction conditions, the scope of the microwave-assisted approach has been extended by using 1,1,1-trifluoroacetophenone and wide selection of substituted amines as reaction partners. The results are summarized in .

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  • imine formation -- is acid catalyzed.

    J., 2-Symmetric Macrocyclic Carbohydrate/Amino Acid Hybrids through Copper(I)-Catalyzed Formation of 1,2,3-Triazoles.

  • Amine synthesis by imine reduction - Organic chemistry

    ChemInform Abstract: NaOH-Catalyzed Imine Synthesis: Aerobic Oxidative Coupling of Alcohols and Amines.

  • Imine synthesis by oxidation, condensation, …

    The mechanism for the acid-catalyzed hydrolysis of esters (and transesterification).

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Imine Formation - California State University, Dominguez …

Masayuki Wasa received his Ph.D. from the Scripps Research Institute in 2013 under the direction of Prof. Jin-Quan Yu before conducting postdoctoral studies with Prof. Eric N. Jacobsen at Harvard University as the JSPS postdoctoral fellow. In 2015, he joined Boston College as an assistant professor. His research interests include development of practical synthetic methods using frustrated acid/base pair catalysts.

There is a biological example of this reaction

A Convenient Synthesis of 1,4,5-Trisubstituted 1,2,3-Triazoles via 1,3-Dipolar Cycloaddition/Coupling of Alkynes, Phenylboronic Acids, and Sodium Azide Catalyzed by Cu(I)/Cu(II).

The hydroxy group is pervasive in chemistry and biochemistry

During these studies we have observed that few CF3-ketones, such as 9-trifluoroacetyl-anthracene, 1-trifluoroacetylnaphthalene and 3-trifluorocetylindole have shown strong resistance toward reaction. Only 1-trifluoroacetylnaphthalene underwent K-10 catalyzed reaction with a vast excess of amine and much longer irradiation period. The remaining two ketones are so deactivated that they do not show any product formation even after excess amine or extended time of irradiation. The use of the solid superacidic perfluorinated resinsulfonic acid, Nafion-H, partially overcame the problem of reactant deactivation. As Nafion-H appeared to be unstable under microwave irradiation (), the reactants and Nafion-H were mixed in toluene and heated up in a pressure tube to 175 °C by conventional heating. Nafion-H under these condition provided some product formation but in only low yields in the case of trifluoroacetylnaphthalene and indole, respectively. In the case of trifluoroacetylnaphthalene a subsequent isomerization has also been observed. With 9-trifluoroacetylanthracene the product was obtained in traces only. It is very likely that the presence of an orthogonal C-H bond e.g. at the naphthyl 8-position interferes with the stabilization of the imine form, leading to an increased stability of the tetrahedral intermediate. The important role of this interaction is clearly supported by the data, that trifluoroacetylnaphthalene with one such interaction gives low yield, while 9-trifluoroacetylanthracene with two such interactions gave the product only in traces.

Palladium-Catalyzed Transformations of Alkyl C–H …

In conclusion, a novel, effective solid acid/superacid catalyzed, economic and environmentally benign method for synthesis of novel trifluoromethylated Schiff bases have been developed. The combination of microwave irradiation and solid acid catalysis greatly reduced reaction time, while improving the yields and making the synthesis of a diverse group of CF3 imines possible. The short reaction time, mostly solvent-free reaction conditions, ease of product isolation, and the safe nature of the catalysts make the process an attractive alternative for the synthesis of trifluoromethylimines in an environmentally benign manner.

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