CH Acids (ch + acid)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

The Acidity of Brønsted CH Acids in DMSO , The Extreme Acidity of Nonacyanocyclononatetraene

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2004
Robert Vianello
Abstract The gas-phase (GP) acidity of a large variety of CH organic acids is studied by a carefully selected B3LYP/6-311+G(2d,p)//B3LYP/6-31G(d) theoretical model. Acidities are mirrored by the proton affinities of the corresponding conjugate bases. A very good agreement with available experimental data is achieved. It is concluded that the model applied has a high predictive value and that theoretical PA(anion)GP values can be used instead of measured data in cases where experiments are not feasible or not performed. It is shown, employing the isodensity polarized continuum model (IPCM), that there is a good linear relationship between the enthalpies of the proton-transfer reactions in DMSO and the observed pKa(DMSO) values. This relation can be used in predicting the acidity of strong, neutral organic superacids. As an illustrative case, the acidity of cyclononatetraene-1,2,3,4,5,6,7,8,9-nonacarbonitrile ("nonacyanocyclononatetraene") is considered. It is conclusively shown that this compound should be a very potent superacid, as evidenced by its PA(anion)GP (260.0 kcal·mol,1) and pKa (,14.8). The origin of high acidity is identified as a very strong anionic resonance effect in the resulting conjugate base. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

ChemInform Abstract: Regioselective Palladium-Catalyzed Prenylation of CH Acids in the Presence of Diamidophosphite Ligands and Potassium Carbonate.

CHEMINFORM, Issue 35 2009
Andrei A. Vasil'ev
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Synthesis of Functionalized 1-Azadienes by Reaction of 2,6-Dimethylphenyl Isocyanide and Acetylenic Esters in the Presence of CH Acids.

CHEMINFORM, Issue 40 2007
Issa Yavari
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Formation of N-Cyclopropylhydrazones by Azo Coupling of Cyclopropyldiazonium with Aliphatic CH Acids.

CHEMINFORM, Issue 44 2003
Yu. V. Tomilov
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Development of Pharmaceutical Drugs, Drug Intermediates and Ingredients by Using Direct Organo-Click Reactions

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2008
Dhevalapally B. Ramachary
Abstract Here we report on our studies of the use of combinations of amino acids, amines, K2CO3 or Cs2CO3 and CuSO4/Cu for catalysing green cascade reactions. We aimed to prepare the highly reactive and substituted olefin species 7 and 8, under very mild and environmentally friendly conditions, thus giving the hydrogenated products 10 and 12 through the action of Hantzsch ester (4) by self-catalysis through decreasing the HOMO,LUMO energy gaps between olefins 7/8 and Hantzsch ester (4) through biomimetic reductions. Highly useful compounds 10 to 14 were assembled from simple substrates such as aldehydes 1, ketones 2, CH acids 3, Hantzsch ester (4) and alkyl halides 5 by diversity-oriented green synthesis involving cascade olefination/hydrogenation (O/H), olefination/hydrogenation/alkylation (O/H/A) and hydrogenation/olefination/hydrogenation (H/O/H) reaction sequences in one-pot fashion with stereospecific organo- and organo-/metal-carbonate catalysis. Highly functionalized diverse compounds such as 10 to 14 are biologically active products and have found wide applications as pharmaceutical drugs, drug intermediates and drug ingredients. For the first time in organocatalysis, we report the O/H/A/TE reaction to furnish high yields of transesterification products 11 by simply mixing the reactants under proline/K2CO3 catalysis conditions. Additionally, a novel organocatalytic H/O/H reaction sequence for the synthesis of alkyl-substituted aromatics has been developed. Furthermore, for the first time we have developed organocatalysed cascade olefination/hydrogenation/hydrolysis (O/H/H) reactions to furnish highly useful materials such as 2-oxochroman-3-carboxylic acid (14kc) and 2-amino-4H -chromene-3-carbonitrile (14kj) in good yields. Experimentally simple and environmentally friendly organocatalytic two-carbon homologation through cascade O/H/H reactions of aldehydes 1, Meldrum's acid (3c), Hantzsch ester (4) and acetic acid/triethylamine in ethanol has been demonstrated. Additionally, we have developed a green synthesis of the highly substituted 1,2,3-triazole 17 from simple substrates through a two-step combination of olefination/hydrogenation/alkylation and Huisgen cycloaddition reaction sequences under stereospecific organocopper catalysis conditions. In this paper we have found strong support for our hypothesis that, "decreasing the HOMO,LUMO energy gap between olefins 7/8 and Hantzsch ester (4) will drive the biomimetic hydrogenation reaction by self-catalysis". This self-catalysis was further confirmed with many varieties of examples.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]