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Direct Condensation (direct + condensation)
Selected AbstractsSynthesis of Sulfinimines by Direct Condensation of Sulfinamides with Aldehydes Using Cs2CO3 as an Activating and Dehydrating Reagent.CHEMINFORM, Issue 26 2004Shuhei Higashibayashi No abstract is available for this article. [source] ChemInform Abstract: Formation of Carboxamides by Direct Condensation of Carboxylic Acids and Amines in Alcohols Using a New Alcohol- and Water-Soluble Condensing Agent: DMT-MM.CHEMINFORM, Issue 27 2001Munetaka Kunishima Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] Solvent-Free Microwave-Assisted Efficient Synthesis of 4,4-Disubstituted 2-OxazolinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2003Fernando García-Tellado Abstract 4,4-Disubstituted 2-oxazolines have been synthesized by a microwave-promoted solvent-free direct condensation of carboxylic acids and disubstituted ,-amino alcohols in good to excellent yields. Zinc oxide is a very good solid support in cases where a Lewis acid is required. The method described herein is a very good, safe, clean, economical, and environmentally friendly alternative to the classical procedures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] The Heteropolytungstate Core {BW13O46}11, Derived as Monomer, Dimer, and TrimerCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2007Nathalie Leclerc-Laronze Dr. Abstract A study of the borotungstate system has led to the characterization of new, original compounds based on the unconventional Keggin derivative [H3BW13O46]8, ion (denoted as 1). [H3BW14O48]6, (2) and the dimer [H6B2W26O90]12, (3) crystallize as mixed cesium/ammonium salts and have been characterized by single-crystal X-ray diffraction analysis. Anion 2 reveals an unusual arrangement, consisting of an outer {W3O9} core grafted onto the monovacant [BW11O39]9, Keggin moiety and exhibits an unprecedented distorted square-pyramidal arrangement for a cis -{WO2} core. Elemental analysis, supported by bond distance analysis, is consistent with the presence of three protons distributed over the terminal oxygens of the outer {W3O7} capping fragment. The [H6B2W26O90]12, ion (3) is formally derived from the direct condensation of two [H3BW13O46]8, subunits. The cisoid arrangement of the two [BW11O39]9, subunits, coupled with the antiparallel arrangement of the two quasi-linear OW,,,OWOH2 chains within the central {W4O12} connecting group, breaks any symmetry, thereby resulting in a chiral compound. Polarography and pH-metric titrations reveal the formation of the monomeric precursor [H3BW13O46]8, (anion 1) under stoichiometric conditions. 183W NMR analysis of 2 and 3 in solution gives complex spectra, consistent with the presence of equilibria between several species. In the frame of this study, we also report on a structural re-investigation of the [H6B3W39O132]15, ion (4) based on reliable results obtained in the solid state by means of single-crystal X-ray diffraction analysis, and in solution by means of 1D and 2D COSY 183W NMR. X-ray diffraction analysis revealed the presence of three attached aquo ligands on the central {W6O15} connecting core, generating three OW,,,OWOH2 quasi-linear chains, which are responsible for the chirality of the trimeric assembly. This structural arrangement accounts for the 39-line 183W solution spectrum. The 2D COSY spectrum permits reliable assignments of the six strongly shielded resonances (around ,250 and ,400,ppm) to the six central W atoms, as well as additional assignments. The origin of such strong shielding for these particular W atoms is discussed on the basis of previously published results. Infrared data for compounds 1, 3, and 4 are also presented. [source] | ||||||||||