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Oxide Nanoparticles in Heterogeneous Catalysis
Published in Varun Rawat, Anirban Das, Chandra Mohan Srivastava, Heterogeneous Catalysis in Organic Transformations, 2022
Garima Sachdeva, Jyoti Dhariwal, Monika Vats, Varun Rawat, Manish Srivastava, Anamika Srivastava
Furanones are five-membered heterocyclic compounds having lactone rings in their structures, and they are present as the core structure of many bioactive natural products and drugs. Tekale and co-workers had established an effective method for synthesis of 3,4,5-trisubstituted furan-2(5H)-ones from aldehyde, amines, and dimethylacetylenedicarboxylate (DMAD) using nano-ZnO as reusable heterogeneous catalyst. The methodology is preferable due to its simplicity, short reaction time, high yield, and cheap heterogeneous catalyst (Figure 2.10) [27]. The first step in the mechanism involves the formation of enamine from amine and DMAD. ZnO polarizes the carbonyl group to generate a polarized adduct, which interacts with enamine, cyclizes, and eliminates the methanol molecule.
Aldehydes and Ketones. Acyl Addition Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
An enamine is a molecule that has an amino group (NR2) attached directly to a carbon–carbon double bond. This particular example is the diethylamino enamine of pentan-2-one, named N,N-diethylpent-1-en-2-amine.
Synthesis of highly functionalized hydropyridones: thiazolo[3,2-a]pyridin-5-one-6-carbohydrazones and tetrahydroimidazo[1,2-a]pyridin-5-one-2-carbohydrazones
Published in Journal of Sulfur Chemistry, 2020
Masoud Mohamadi Vala, Mohammad Bayat, Yadollah Bayat
A proposed mechanism for the formation of (E)-N′-(arylidene)-7-(aryl)-8-nitro-5-oxo-2,3,6,7-tetrahydro-5H-thiazolo[3,2-a]pyridine-6-carbohydrazide 6 is shown in Scheme 7. First, the reaction between diamine 1 and nitroethene 2 affords ketene aminal A, While the condensation of aldehyde 3 with 4 furnishes adduct B. Then, the α-C of ketene aminal A attacks the C = C bond of the B to generate the intermediate Dvia a Michael reaction. The intermediate D form the intermediate Evia imine-enamine tautomerization. Next, the amino group attacks to the cyano group, leading to the formation of 5. Second, addition of H2O to compound 5 in the presence of H+ furnishes intermediate G, and proton transfer between H2O+ and NH2 affords intermediate H which undergoes elimination of NH3, followed by successive enol-keto tautomerization led to the formation of product 6.
Near-threshold electron transfer in anion-nucleobase clusters: does the identity of the anion matter?
Published in Molecular Physics, 2019
Rosaria Cercola, Edward Matthews, Caroline E. H. Dessent
In the TRPEI study of I−·A [20], two adenine isomers were observed in the clusters: the biologically relevant A9 isomer and the A3 isomer. Adenine is well-known to exist in fourteen stable isomers, with the amine forms A9, A7 and A3 being lower in energy than the enamine/imine forms [21]. The A9 isomer is computed to be the lowest energy isomer in the gas-phase, while the A7 isomer is stabilised in polar solvents and in polar clusters due to its large dipole moment [21]. A dipole-bound anion of the A9 tautomer has been observed via Rydberg electron transfer, with an associated electron affinity of + 12 meV [22]. However, the dipole-bound anions of the A7 and A3 tautomers have not been observed to date, despite having larger dipole moments than A9 [23]. From a number of experimental and theoretical studies, the valence bound A9 anion is thought to be adiabatically unstable. Indeed, theoretical calculations by Raczynska et al. suggest that only the A3 isomer forms a stable valence anion [24]. Figure 1 illustrates the structures of the key A9, A7, and A3 isomers.
Advances in self-crosslinking of acrylic emulsion: what we know and what we would like to know
Published in Journal of Dispersion Science and Technology, 2019
Sumit Parvate, Prakash Mahanwar
Nicola Kessel studied the fundamentals of the keto-hydrazide reaction and put forwarded for the first time, that the reaction yields an imine and not enamine.[79] While it was made known that primary amines and carbonyl groups gives imines, whereas enamines can be formed on the reaction of aldehydes and ketones with secondary amines. Furthermore, crosslinking reaction was acid catalyzed and the reaction rate was inversely proportional to pH of reaction. The factors like lower latex Tg, higher film formation temperature, and no crosslinking enhances surfactant exudation. Koukiotis et al. studied the effect of various polymerizable and non-polymerizable, free of alkylphenol ethoxylates (APEO-free) surfactants on film properties. They have testified that non-polymerizable surfactants showed very high coagulum, whereas polymerizable surfactant gave almost zero coagulum. In addition, crosslinking helped in the coalescence of the particles which resulted in better scratch resistance, low MFFT, and higher gloss. Water absorption was increased because of hydrophilicity of the ADH and might be due to possibility of unbounded groups (–NH–NH2) of ADH on DAAM [80]