Reaktionsprodukte aus Antimon(V)-chlorid und N,N′-Dimethyloxamid und deren Schwingungsspektren

Reaction Products of Antimony(V) Chloride and N, N′-Dimethyloxamide and their Vibrational Spectra N, N′-Dimethyloxamide reacts with antimony(V) chloride at lower temperatures to the 1:1 resp. 1:2 addition compounds I resp. II. Pyrolysis of these compounds leads to the cyclic tetrachloroantimony(V)-N, N′-dimethyloxamides (III) resp.(V). III yields with antimony(V) chloride the 1:1 adduct IV, which is transformed to V. The vibrational spectra were assigned and discussed.     

Synthesis and Structure Investigations of Potential Sedative and Anticonvulsant Hydroxy- and Acetoxy-N-(3-oxobutyl)-pyrido[2,3-d]pyridazinonesa

Summary.  Novel N-(3-oxobutyl)-hydroxy- and acetoxypyrido[2,3-d]pyridazinones were synthesized and tested in vivo for their sedative and anticonvulsant activity. The Michael-type reaction of quinolinic acid hydrazide and methyl vinyl ketone afforded a mixture of two isomers, 5-hydroxy-N ⁷-(3-oxobutyl)-pyrido[2,3-d]pyridazin-8(7H)-one and 8-hydroxy-N ⁶-(3-oxobutyl)-pyrido[2,3,-d]pyridazin-5-(6H)-one, in a ratio of 2:1 which were separated by crystallization. Subsequent acetylation of both isomers yielded the corresponding 5- and 8-acetoxy compounds. The structures of the compounds were proven and completely assigned on the basis of ¹H, ¹³C, ¹⁵N NMR, and 1D NOE difference spectra as well as 2D C,H-correlation experiments. Preliminary pharmacological tests showed low acute toxicity with a LD ₅₀ > 1000 mg/kg in the mouse and sedative activity for the title compounds. 5-Acetoxy-N ⁷- (3-oxobutyl)-pyrido[2,3-d]pyridazin-8(7H)-one displayed a borderline anticonvulsant activity in the metrazole test model. Corresponding author. E-mail: edith.goessnitzer@uni-graz.at Received March 20, 2002; accepted April 3, 2002     

Zur Kenntnis des Calciumbromats und - iodats,Kristallstruktur, röntgenographische,IR- und Raman-spektroskopische und thermoanalytische Untersuchungen

On Calcium Bromated and Iodates – Crystal Structure, X-Ray, IR and Raman Spectroscopical and Thermoanalytical Investigations The phase relationships (and both decomposition and disproportionation)of bromates and iodates of alkaline earth metals are studied by means of thermal analyses (DTA, DSC, TG) and (high-temperature) X-Ray, IR-, and (high-temperature) Raman spectroscopic measurements. The following compounds have been established: Ca(IO₃)₂ · 6 H₂O oF 216, the isotypic Ca(BrO₃)₂ · H₂O and Ca(IO₃)₂ · H₂O mP 48, Ca(IO₃)₂ I (Lautarit) mP 36, Ca(IO₃)₂ II and Ca(BrO₃)₂. The Crystal structure of Ca(IO₃)₂ · H₂O (brüggenite) (space group P2₁/c, Z = 4) has been determined by single crystal X-ray diffraction (MoKα). The final R value for 3888 reflections with I_o > 3σ₁ is 0.0487. The structures of bromates and iodates of alkaline earth metals known so far are discussed with respect to the energetic (mode frequencies) and geometric (bond lengths) distortion of the XO₃–ions as well as the strengths of H-bonds present in the respective hydrates.     

Synthese und Abbau von 1-(5-Nitro-2-thiazolyl)-2-imidazolidinon und Derivaten

1-(5-Nitro-2-thiazolyl)-2-imidazolidinone is synthesized from 2-amino-5-nitro-thiazole and 2-chloroethyl-isocyanate. The structure of this new potent schistosomicide is established by acid and alkaline degradation as well as by synthesis starting from 2-imidazolidinone. A number of derivatives of 1-(5-nitro-2-thiazolyl)-2-imidazolidinone are reported.     

Electrospray ionization mass spectrometric studies of nucleophilic carbenes derived from pyrazolium and indazolium carboxylates

Pyrazolium-3-carboxylate and indazolium-3-carboxylate, which belong to the class of pseudo-cross-conjugated mesomeric betaines and which represent the electronically relevant partial structures of the betaine alkaloid Nigellicin, were examined by electrospray ionization mass spectrometry. These compounds decarboxylate to pyrazol-3-ylidene and indazol-3-ylidene. The formation of adducts of these new nucleophilic carbenes under the measurement conditions was examined.     

Gaseous alkyne ions

Using the relative abundance of metastable ions, collisional activation spectra, field ionization kinetic measurements, isotopic labelling, appearance energy and kinetic energy release data, it is shown that linear alkyne radical cations with more than six carbon atoms do not isomerize to equilibrating structures prior to decomposition. At the shortest ion lifetimes the molecular ions of linear alkynes decompose mainly by simple β-bond fission which allows an unequivocal localization of the triple bond. At medium ion lifetimes fragmentation occurs predominantly via a McLafferty rearrangement, while at long ion lifetimes competing alkyl losses prevail. These alkyl losses occur via cyclic intermediates leading to thermochemically stable cycloalkenyl ions. All these reactions occur with a high specificity with respect to the carbon and hydrogen atoms involved and are preceded by little or no hydrogen exchange reactions.     

Über die Reaktionen von Guanidin bzw. Thioharnstoff mit α,β,γ,δ-ungesättigten Ketonen

Guanidine and phenylguanidine react with phenylhexadienone1b and 1,5-diaryl-2,4-pentadien-1-ones1c–k respectively (via unstable dihydropyrimidines of type2 as intermediates) to 4-methyl- and 4-aryl-6-styryl-2-pyrimidinamines3b–j and N²-phenyl-2-pyrimidinamines7c, k. Efforts to stabilize the intermediates2 by introduction of electron-withdrawing substituents (compare^2,3) were not successful. Similarly, thiourea reacts with diphenylpentadienone1c to afford (via8c) 4-phenyl-6-phenethylpyrimidinethione9c. Action of guanidine on 1,3,5-triphenylpentadienone101 and on the 5-(3-chlorophenyl) analogue10m under decomposition of the ketones yields 4,6-diphenyl-and 4-(3-chlorophenyl)-6-phenyl-2-pyrimidineamine (121 andm), respectively. The formation of12m proves that acetophenone splits off from101,m during the reactions. However, heating of thiourea with10m in sodium butylate/butanol gives the expected 4,6-diphenyl-4-styryldihydropyrimidinethione13m. The reaction of thiourea with triphenylpentadienone101 is taking an atypical course: Addition of thiourea to the δ- and β-carbon atom of101 affords 2-(4,6-diphenyl-2-thioxohexahydro-4-pyrimidinyl)acetophenone (141); the conformation of the latter was deduced from¹H-NMR data.     

Conformational structure of N-methylpropionamide and N-methylisobutyroamede. NMR shift reagent and IR study

The structures of the stable conformers of N-methyjpropionamide and N-methyliso-butyroamide in CCl₄, solution were determined by a combination of IR spectroscopy and NMR spectroscopy with lanthanide shift reagents. N-methyl-propionamide was found to exist in the form of two rotational isomers, 1 and 2, with the ethyl group twisted out of the plane of the amide bond by the angles Ψ = 140 and 20°, respectively. For these two conformers, the enthalpy difference is ΔH = 2.13 ± 0.08 kcal mole^?1 and the entropy difference ΔS = 7.81 ± 0.55 cal mole^?1 grad^?1. N-methylisobutyroamide exists in a single form, with the two C-methyl group positions very close to those found in the two isomers of N-methylpropionamide.     

Thermochemical Investigations of Calcium Carbonate Phase Transitions I. Thermal activated vaterite—calcite transition

The vaterite—calcite transition above 630 K has been studied by isothermal and non-isothermal differential scanning calorimetry. Vaterite samples prepared under different conditions were investigated. The transition temperature is strongly dependent on the sample preparation. The observed transition enthalpy H_tr is nearly equal for different samples and experimental conditions. From 28 measurements a value of H_tr–(3.12±0.11) kJ mol^–1 was obtained. The activation energy for the polymorphic transition was calculated from the Arrhenius plot and by use of isoconversional methods, as a function of the degree of conversion. The influence of the kinetic model distortion and experimental uncertainties on the obtained data was discussed. The actual value of the activation energy was assessed at E_a=(250±10) kJ mol^–1 for nearly all examined samples. Functions, corresponded to the model mechanism of nuclei formation and growth, provide the unambiguous consideration of the transition kinetic for the investigated vaterite samples. Differences in the dynamic behaviour of several samples at the transition are established.This revised version was published online in November 2005 with corrections to the Cover Date.     

Neue Verbindungen mit Granatstruktur. III. Arsenate des Typs {NaCa2} [M] (As3)O12

Attempts to prepare phosphate granates were without success. However, three arsenate granates of the type {NaCa₂}[M](As₃)O₁₂ with M^II ? Mg, Co, Ni have been prepared by solid state reaction and their lattice constants determined. All these arsenates are characterised by a thermal transformation into a high-temperature form, proceeding monotropically for the Mg compound, and reversibly for the Ni and Co compound.