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2-Azabicyclo[2.2.2]octa-2,5-diene derivatives 2 are obtained from alkylidenemalononitriles using sodium methoxide. Several of these bicyclo compounds smoothly undergo retro-Diels-Alder with the loss of the hydrocarbon moiety to give the corresponding pyridine derivatives 3 when heated in xylene or acetic acid.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAtropisomerism in metal chelates. Preparation and partial resolution of (3,4-diacetyl-2,5-hexanedionato)bis[(2,2',2"-triaminotriethylamine)cobalt(III)] ionYoshiharu Nakano and Yuzo YoshikawaCite this: J. Am. Chem. Soc. 1984, 106, 2, 429–430Publication Date (Print):January 1, 1984Publication History Published online1 May 2002Published inissue 1 January 1984https://pubs.acs.org/doi/10.1021/ja00314a033https://doi.org/10.1021/ja00314a033research-articleACS PublicationsRequest reuse permissionsArticle Views57Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
The crystal structure of N,N′-diphenyl-2,6-bis(tosylaminomethyl)pyridine 3a and N,N′-dibenzyl-2,6-bis(tosylamino-methyl)pyridine 3b were determined. The structures were solved by the direct method and refined to R = 0.040 and R = 0.039, respectively. Tosylamide 3a has a symmetric structure, but 3b has a complicated asymmetric conformation, unexpectedly. All oxygen atoms of the tosyl group are opposite side to the pyridine nitrogen.
The novel tetranuclear copper(II) complex [Cu4(hpda)4][ClO4]4·H2O (Hhpda = N-(2-hydroxyethyl)-1,3-propanediamine) with an open cubane-like Cu4O4 framework has been obtained and characterized by X-ray crystallography and magnetic measurements, exhibiting strongly ferromagnetic exchange interaction.
Abstract A new ligand, 3-(1-naphthyl)-2,4-pentanedione, was prepared. Concentration proton-dissociation constants of 3-aryl-2,4-pentanedione (aryl group; phenyl, 2,4-dinitrophenyl, and 1-naphthyl) and concentration stability constants of some bivalent metal chelates of 3-aryl-2,4-pentanedione were determined in a 75% v/v 1,4-dioxane–water medium containing 0.05 mol dm−3 sodium perchlorate by a pH-titrimetric method. The dissociation constant (pKa) of 3-(2,4-dinitrophenyl)-2,4-pentanedione, 2,4-pentanedione, 3-phenyl-2,4-pentanedione, and 3-(1-naphthyl)-2,4-pentanedione were found to be 8.87, 10.93, 11.50, and 11.71, respectively. The order of acidity in 2,4-pentanedione was explained by the field effect of the aryl group. The stability constants of the bivalent metal chelates of these ligands were in accord with the Irving-Williams series. The stepwise stability constant of the chelate increased with an increasing pKa value of 3-aryl-2,4-pentanedione. This result cannot be explained by the steric and solvation effect of an aryl substituent.
Abstract magnified image A facile preparation and the crystal structures of N, N ′‐dialkyl‐2,6‐ pyridinedimethanaminium halides were described. Direct substitution reactions were convenient to prepare specifically secondary diamines using 2,6‐bis(chloromethyl)‐ pyridine and 10 equivalents molar of primary alkylamines. Hydrogen halide salts were obtained in good yields and the crystal structures of three N, N ′‐dialkyl‐2,6‐pyridinedimethanaminium salts were determined by the X‐ray diffraction method. A cancroid structure around the pyridine ring was observed commonly in the three salts. Acidity constants of the three salts were determined. Since the pKa values of the salts were slightly smaller than those of several common triamines previously reported, the acidities did not correlate with the cancroid structure directly. This is probably due to electrostatic interaction of the two protonated amino groups, furthermore the central pyridine nitrogen was not protonated in all the ligands.
