Langsame Inversion am pyramidal gebundenen Stickstoff: Isolierung und Epimerisierung diastereomerer N-Methoxy-3,3-di-methoxycarbonyl-5-cyan-1, 2-oxazolidine. Vorläufige Mitteilung

Two crystalline diastereomeric N-methoxy-3, 3-di-methoxycarbonyl-5-cyano-1, 2-oxazolidines (II and III) have been isolated. The pyramidal arrangement at the respective nitrogen atoms does not invert at room temperature. The ARRHENIUS activation energy for the epimerization of the thermodynamically less stable isomer to the more stable one in bromoform solution is 29,2 ± 0,5 kcal/Mol (log A = 14,2 ± 0,3).     

Langsame Inversion am pyramidal gebundenen Stickstoff: Konfiguration und Konformation beim Strukturtyp der N,N-Dialkoxy-alkylamine aus der Sicht eines semiempirischen MO-Modells

Nitrogen inversion and rotation around the N-O single bond in N, N-dialkoxyalkylamine systems are discussed in terms of a semi-empirical MO method which is essentially based on the concepts discussed by Mulliken in connection with the “magic formula”. By taking a simplified structural model and adjusting one empirical parameter, a satisfying agreement with experimental results is obtained. The results allow a chemically transparent interpretation and confirm, to a more quantitative extent, the previously discussed concepts [1]. The (sp^x → p) promotion of the nitrogen lone pair strongly inhibits the inversion process and dominates the simultanous lowering of the σ-bond energies due to (i) the gain of s-character in the σ-involved nitrogen hybrid-AO's and (ii) the increased σ-bond overlaps. This dominance is considerably enhanced when electronegative ligands are attached to nitrogen. The total repulsion energy turns out to favour strongly the planar transition state and is essentially determined by the repulsions between the lone pair and the σ-bonds at nitrogen. Factorization into several repulsive contributions reveals that among these only one inhibits the inversion process, namely the repulsions between the nitrogen lone pair and the bonded and non-bonded electron pairs on the ligands. For the process of rotation around the N-O single bond a potential curve is obtained with two energy minima. The repulsion energy analysis shows that the shape of the potential curve is governed by the repulsions between the lone pairs on oxygen and nitrogen as well as the formally more or less “lone pair-like” σ_NC-bond. This situation is compared to the more general one in which essentially two lone pairs or formally more or less “lone pair-like” σ-bonds, on each of two adjacent centers, repel each other by conjugative destabilization; a situation which is realized for instance in molecules that show the anomeric effect.     

Kristallstrukturanalyse des AsCl2F3

The X-ray analysis of AsCl₂F₃ is described. Crystals of this compound are isomorphous with PCl₅ (space group \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm P}\frac{{\rm 4}}{{\rm n}} $\end{document} a = 8.75, c = 6.23 Å). The atomic parameters were refined by the method of least squares. The compound is heteropolar and consists of tetrahedral cations AsCl₄⁺ and octahedral anions AsF₆^?.     

Cyclisierung von 3-Acylmethylthio-4-cyan-2H-isothiazol-5-thionen

The title compounds2 cyclize on mild conditions to the intermediate 7-cyano-thiazolo[3,2-b]isothiazole-6-thiones3 which are converted immediately into the 1,2,4-trithiolane-3,5-diylidene-(thiazole-2-yl)-acetonitriles4 accompanied by extrusion of sulphur. The cyclization of the 4-cyano-5-methylthio-3-phenacylthio-isothiazole (6) yields the 7-cyano-6-methylthio-thiazolo[3,2-b] isothiazoliumsalt7 which undergoes reductive ring opening by hydrazine hydrate to yield methyl (4-phenyl-thiazolin-2-ylidene)-cyanodithioacetate (8).     

Präparation und Kristallstrukturanalyse von Ca(N3)2(C5H5N)2

Diazido-dipyridine-calcium was prepared by the reaction of Ca(N₃)₂ with pyridine. The crystals are tetragonal, space group I 2 m (121),N=2,a=699.7 (1),c=1 450.6 (5) pm. The crystal structure was determined by single crystal X-ray diffraction, 415 independent observed Mo-K-counter reflexions,R=0.049. The calcium atoms are sixcoordinated to four nitrogen atoms of azide groups and to two nitrogen atoms of pyridine. The coordination polyhedra are tetragonal bipyramids which are linked together by four azide groups to form sheets of composition Ca(N₃)₂. The pyridine rings are directed perpendicular to the sheets.

     

Metall-π-Komplexe des 2, 5-Diphenyl-1-silacyclopentadiens

The preparation of 2.5-diphenyl-1-silacyclopentadienes and their reaction with iron carbonyls and π-cyclopentadienyl-dicarbonylcobalt yielding metal-π-silole complexes is described. Mass spectral data indicate the existence of an ‘aromatic’ silacyclopentadienyl species.     

Versuche zur Synthese des 1, 5-Diaminopentanols 3

Ohne Zusammenfassung     

2-Methyl-3-nitro-4-methoxymethyl-5-cyanpyridon (NCP) und 2-Methyl-3-nitro-4-methoxymethyl-5-cyan-6-chlorpyridin (CHP)

Ohne Zusammenfassung     

Die Hydrolyse des 1, 1, 3, 3-Tetrakis(dimethylamino)-1λ5, 3λ5-diphosphets

Hydrolysis of 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵, 3λ⁵ -diphosphete Hydrolysis of 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵, 3λ⁵ -diphosphet ( 2 ) yields in the first step Bis(dimethylamino)phosphorylmethyliden-methyl-bis(dimethylamino)phosphorane ( 5 ). In the second step Bis(dimethylamino)phosphoryl-methyl(dimethylamino)phosphosphonylmethylen ( 6 ) is the main product of hydrolysis. In addition small amounts of methylphosphonic-bis(dimethylamide) ( 7 ) are formed. Properties, nmr and mass spectra of 5 and 6 are described, their mechanism of formation is discussed.     

Synthese und Kristallstrukturanalyse von NaSrMg2F7, einer vollständig fluorierten Verbindung des Pyrochlortyps

Synthesis and Crystal Structure Analysis of NaSrMg₂F₇, a Fully Fluorinated Compound of the Pyrochlore Family During our research on alkali‐fluorides, the compound NaSrMg₂F₇ has been prepared by a precipitation reaction of Sr²⁺, Mg²⁺ and Na⁺ with F^– for the first time. The powder crystallizes as a single phase in the form of spherical agglomerates ∼0.25 μm in diameter. The compound crystallizes in the space group Fd 3 m (Nr. 227) with lattice parameter a = 10.4379(4) Å. Structural analysis by the Rietveld method was done from X‐ray diffraction data. In agreement with the structure analysis, spectroscopical investigations confirm the presence of two coupled fluoride ions. The crystal structure corresponds to the pyrochlore structure type A₂B₂X₇ with 50% occupation of Sr²⁺ or Na⁺ at the A site.     

Strukturelle Abwandlungen am Vitamin D3. 3. Mitteilung [1]. Synthese und eigenschaften von SO2-addukten des (5Z)- und (5E)-vitamins D3

Structural Modifications of Vitamin D₃. Synthesis and Properties of the SO₂-Adducts with (5 Z )- and (5 E )-Vitamin D₃ Treatment of (5Z)- and (5E)-vitamin D₃ ( 4 ) with sulfur dioxide yields each quantitatively the cyclic sulfones 1a and 1b . Thermally induced elimination of sulfur dioxide leads to either isotachysterol₃ ( 3 ) alone or mixtures of isotachysterol₃ ( 3 ) and isovitamin D₃ ( 2 ). On the other hand the extrusion of SO₂ can be brought about by means of KOH/CH₃OH or on an alumina surface affording (5E)-vitamin D₃ ( 4 ). On treatment with CD₃UD/tBuOK/D₂O 1a and 1b are transformed (5E)-6, 19, 19′-trideuteriovitamin D₃ ( 4a ).     

Some 2-aryl-5-azaindandiones-1, 3

Condensation of cinchomeronic acid with p-nitrophenylacetic acid, of 2, 6-dimethylcinchomeronic acid with phenylacetic acid, and p-nitrophenylacetic acid in acetic anhydride solution in the presence of triethylamine followed by rearrangement of the condensation products with sodium methoxide gives 2-(p-nitrophenyl)-5-azaindandione-1, 3, 4, 6-dimethyl-2-phenyl-5-azaindandione-1, 3, and 4, 6-dimethyl-2-(p-nitrophenyl)-5-azaindandione-1, 3. Reaction of the alkali metal salts of these compounds with dimethyl sulfate leads to alkylation at the nitrogen atom, and formation of N-methyl betaines of the corresponding 5-azaindandiones. 2-Aryl-5-azaindandiones and their N-methyl betaines are dark in color (black to reddish brown), sparingly soluble, and decompose at 250-350°.     

2, 5-Dialkyl-1, 3, 4-oxadiazoles

A single stage method has been developed for the preparation of 2, 5-dialky-1, 3, 4-oxadiazoles from aliphatic carboxylic acids, by boiling with hydrazine hydrochloride in phosphoryl chloride. A mechanism for the synthesis is suggested. The oxadiazoles are characterized, and the group refractivity of the 1, 3, 4-oxadiazole ring has been determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1171–1175, September, 1970.     

Derivate des 5, 6-Dihydro-p-dithiin-2, 3-dicarbonsäure-anhydrids,I: Imide

5. 6-Dihydro-p-dithiin-2. 3-dicarboxylic anhydride reacts with primary amines quite readily to form the substituted imides. The imide formation occurs much more easily than with maleic or phthalic anhydride. The imide and all N-substituted imides have a fairly strong, bright yellow colour. Their absorption spectra differ considerably from those of the anhydride, ester and dinitrile. Electron-attracting substituents on the imide nitrogen increase the absorption maximum somewhat, while strongly electron-releasing groups decrease it, and may even shift it to a shorter wave-length. It is therefore concluded that the imide nitrogen is part of the election acceptor group of the chromorphoric system.     

Synthese und Umwandlungen der N-substituierten 3-Aminopropansäuren, 4. Mitt.: Darstellung von unterschiedlich am Stickstoff acylierten 3-Aminopropansäuren nachRitter

Zusammenfassung Die Umsetzung der Äthylester von 3-Hydroxycarbonsäuren mit unterschiedlichen Mono- und Dinitrilen in Gegenwart von Schwefelsäure führt meist zu den jeweiligen 3-(N-Acyl)-amino-carbonsäuren. Andere Versuche ergaben, daß der tert. Butylester der 2-(1-Hydroxycyclohexyl)-äthansäure direkt die erwartete N-Acylaminocarbonsäure liefert. In derselben Weise wurden einige N-Acylderivate der 2-(1-Aminocyclohexyl)-äthansäure synthetisiert, die aus dem Äthylester der eingesetzten Hydroxysäure nicht darstellbar sind.

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Ethyl 3-hydroxycarboxylates react with mono- and dinitriles in the presence of sulfuric acid in most cases with the formation of the corresponding 3-(N-acyl)-amino acids. A direct formation of the N-acyl amino acid was observed in the case of (1-hydroxycyclohexyl)-acetic acidt-butyl ester. Several N-acyl derivatives of (1-aminocyclohexyl)-acetic acid, not obtainable from its ethyl ester, were synthesized using this procedure.

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3. Mitt.: Mh. Chem.98, 2001 (1967).