110449-10-0Relevant academic research and scientific papers
Dynamic Covalent Metathesis in the C=C/C=N Exchange between Knoevenagel Compounds and Imines
Gu, Ruirui,Flidrova, Karolina,Lehn, Jean-Marie
, p. 5560 - 5568 (2018)
Fast and reversible dynamic covalent C=C/C=N exchange takes place without catalyst in nonpolar solvents between barbiturate-derived Knoevenagel (Kn) compounds and imines. A detailed study of the reaction indicates that it proceeds by an associative organo-metathesis mechanism involving the formation of a four-membered ring azetidine intermediate by addition of the imine C=N group to the C=C bond of the Kn compound. This intermediate could be generated cleanly and stabilized at low temperature by condensation of the o,p-dinitrophenyl Kn derivative with the cyclic imine 1-azacyclohexene. It was characterized by extensive NMR and mass spectrometric studies. The process described represents a genuine dynamic covalent organo-metathesis through a four-membered ring adduct as intermediate. It paves the way for the exploration of a wide set of dynamic systems involving (strongly) polarized C=C bonds and various imines, extending also into covalent dynamic polymers and polymolecular assemblies.
An unexpected linear Bronsted correlation
Baumann, Klaus D.,Brighente, Ines M.C.,Pizzolatti, Moacir G.,Yunes, Rosendo A.
, p. 545 - 551 (2007/10/03)
The reaction of barbiturate and 1,3-dimethylbarbiturate ions with o-, p- and 2,4-dinitrobenzaldehyde was studied. The reactions of barbiturate anion with o- and p-nitrobenzaldehyde exhibit a pH-rate profile different to that the corresponding to the reactions of barbiturate and 1,3-dimethylbarbiturate ions with 2,4-dinitrobenzaldehyde. The dependence of the rate constant on the viscosity of the medium in the pH range 2-4, for all the reactions, indicates the contribution of a diffusion-controlled proton transfer from the hydronium ion to an addition intermediate, T-, in the rate-determining step. Surprisingly, in the reaction of 2,4-dinitrobenzaldehyde with barbiturate and 1,3-dimethylbarbiturate anions, the Bronsted plot for general acid catalysis for carboxylic acids of pKa between 2 to 5 gives a linear relationship with a = 0-707 (r = 0.991), whereas a = 0 is expected, considering the pKa of the addition intermediate T-. On the other hand, the point for the rate constant, considering water as a general acid catalyst, falls approximately 105 times above the corresponding Bronsfed line. The tautomerism existing in the intermediate T- permits these surprising facts to be explained.
5-Arylidene 1,3-Dimethylbarbituric Acid Derivatives, Mild Organic Oxidants for Allylic and Benzylic Alcohols
Tanaka, Kiyoshi,Chen, Xing,Kimura, Teiji,Yoneda, Fumio
, p. 60 - 69 (2007/10/02)
Various 5-arylidene 1,3-dimethylbarbituric acid derivatives and closely related compounds were synthesized as models of redox coenzymes and used for oxidation of alcohols.Under mild neutral conditions, 5-arylidene 1,3-dimethylbarbituric acid derivatives, especially those having an electron-withdrawing group on the aromatic ring, effectively oxidized allylic and benzylic alcohols to the corresponding carbonyl compounds.The relationship between the oxidizing ability and the structure of the oxidant (coenzyme model) was investigated and it was found that the electron density on the carbon-carbon double bond is a critical factor for the oxidation.In the case of the deuterium-labeled compound, the observed value of normal and primary isotope effect was 3.3 and so it was concluded that mechanism of this oxidation mainly involves the hydride transfer from the alcohol.An electrochemical investigation was also carried out and the redox potentials of the coenzyme models, 5-arylidene 1,3-dimethylbarbituric acid derivatives and related compounds, were measured.Keywords - 5-arylidene 1,3-dimethylbarbituric acid; coenzyme model; oxidation; allylic alcohol; benzylic alcohol; oxidation mechanism; hydride transfer; primary isotope effect; cyclic voltammetry; redox potential
