What is the role of acid–acid interactions in asymmetric phosphoric acid organocatalysis? A detailed mechanistic study using interlocked and non-interlocked catalysts

Organocatalysis has revolutionized asymmetric synthesis. However, the supramolecular interactions of organocatalysts in solution are often neglected, although the formation of catalyst aggregates can have a strong impact on the catalytic reaction. For phosphoric acid based organocatalysts, we have now established that catalyst–catalyst interactions can be suppressed by using macrocyclic catalysts, which react predominantly in a monomeric fashion, while they can be favored by integration into a bifunctional catenane, which reacts mainly as phosphoric acid dimers. For acyclic phosphoric acids, we found a strongly concentration dependent behavior, involving both monomeric and dimeric catalytic pathways. Based on a detailed experimental analysis, DFT-calculations and direct NMR-based observation of the catalyst aggregates, we could demonstrate that intermolecular acid–acid interactions have a drastic influence on the reaction rate and stereoselectivity of asymmetric transfer-hydrogenation catalyzed by chiral phosphoric acids.

Supramolecular acid–acid interactions lead to competing monomeric and dimeric pathways in phosphoric acid catalysis – so that stereoselectivities depend on catalyst concentration.     

Ueber die Trennung des Thoriums von den anderen seltenen Erden durch stickstoffwasserstoffsaures Kalium

Ohne Zusammenfassung     

Synthesis and antimalarial effects of N,N-dialkyl-6-(substituted phenyl)-1,2,4,5-tetrazin-3-amines

The synthesis of a series of N,N-dialkyl-6-(substituted phenyl)-1,2,4,5-tetrazin-3-amines (IV) by two routes is described. The first route (Scheme I) involved the oxidative cyclization of formazans (II) to 3-bromo-6-(substituted phenyl)-1,2,4,5-tetrazines (III), followed by treatment with amines. The second (Scheme II) utilized the treatment of 3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VII) with amines to provide the desired products. The intermediate 3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VII) were obtained by thiobenzoylation of hydrazinecarbohydrazonothioic acid methyl ester with [[(substituted phenyl)thioxomethyl]thio]-acetic acids (V) to afford the 1,2-dihydro-3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VI). Oxidation with bromine in acetic acid provided the desired intermediates. The target 6-(substituted phenyl)-1,2,4,5-tetrazin-3-amines (IV) displayed modest antimalarial activity.     

Coordination compounds of indium : XXXVI. The direct electrochemical synthesis of neutral and anionic organoindium halides

The electrochemical oxidation of indium metal in cells of the type leads to the formation of RInX₂ compounds; if 2,2′-bipyridine is also present, the products are the adducts RInX₂·bipy (R = CH₃, C₂H₅, C₆H₅, C₆H₅CH₂, C₆F₅; X = Cl, Br, I (not all combinations)). When R′₄NX is present instead of bipy, the products are the salts R′₄N[RInX₃]. The electrochemical oxidation apparently proceeds via the general mechanism discussed previously. Anomalous results with CH₃I or C₂H₅I are discussed in the light of the known solution chemistry of organoindium(III) compounds.     

Vakuumspektrometrische Analyse gepre?ter Stahlsp?ne

Zusammenfassung Die Vakuumspektrometrische Analyse von Stahlspanpreßlingen wird verbessert und ausgedehnt. Es wird das Abfunkverhalten der Preßlinge unter verschiedenen atmosphärischen Bedingungen in der Funkenkammer beschrieben. Der Zusatz von Wasserstoff zum Argon wirkt sich günstig aus, die Reproduzierbarkeit der Abfunkergebnisse ist gut. Unter den angegebenen Bedingungen lassen sich Spanbriketts aus unberuhigten und beruhigten Stählen einwandfrei vakuumspektrometrisch analysieren.Unberuhigte und beruhigte schwefel-bleihaltige Automatenstähle lassen sich ebenfalls analysieren, wenn die Probenvorgeschichte durch starke Warmverformung und Zerspanung, mit anschließender Mischung und Brikettierung der Späne ausgelöscht wird. Neben der Form hat auch die Größe der Mangansulfid-Bleieinschlüsse einen großen Einfluß auf den Zeit-Intensitätsverlauf aller Spektrallinien.

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Vacuumspectrometric analysis of briquetted steel chips

Improvements on vacuumspectrometric analysis of briquetted steel chips are dealth with. The influence of different atmospheric conditions in the spark chamber on sparking behaviour of briquettes is shown. An addition of hydrogen to the argon gas will give better results, the reproducibility of analysis is very good. A method is given for vacuumspectrometric analysis of briquetted chips, taken from rimming or killed steels.After hot working, milling and briquetting, samples of rimming and killed sulphurized, leaded free-cutting steel can be analysed, too. There is a great influence of the dimension and the shape of the MnS-Pb inclusions on the pre-spark curves.

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Auszug aus der Doktordissertation, Montanistische Hochschule Leoben, 1967.     

Nitrogen atom insertion into Ir-S and C-S bonds initiated by photolysis of iridium(III)-azido-dithiocarbamato complexes

Photolysis of acetonitrile solutions of Cp*Ir(R2dtc)(N3) [Cp* = eta5-C5Me5, R2dtc = S2CNR2; R = Me (1) or Et (1')] at temperatures below 0 degrees C afford five-coordinate complexes Cp*Ir{NSC(NR2)S} (2 or 2'), where a nitrogen atom has been inserted into one of the Ir-S bonds. In solution, complex 2 thermally convert to the azaethene-1,2-dithiolate complex, Cp*Ir[SN=C(NMe2)S] (3), which could be crystallized as the corresponding dimer, {Cp*Ir[mu-SN=C(NMe2)S-kappa3S:S,S']}2 (4). As a result, a nitrogen atom that originated in the azide ligand is transferred into a C-S bond of the dithiocarbamate.     

Reissert compound studies. Cyclization of N-(ω-chloroalkanoyl)reissert compounds

Treatment of 2-(4-chlorobutanoyl)- and 2-(5-chloropentanoyl)-1, 2-dihydroisoquinaldonitrile with sodium hydride gave rise to tricyclic benzoquinolizone and azepino[1,2-α]isoquinoline derivatives. A similar reaction was observed in the quinoline series. Several reactions of 1,2,3,4-tetrahydro-4-oxo-11bH-benzo[α]quinolizine-11b-carbonitrile are reported.     

Die Kristallstruktur von Si5O[PO4]6

The crystal structure of Si₅O[PO₄]₆ has been determined and refined by least-squares, using three-dimensional X-raydata fromWeissenberg photographs: space group R 3;a=7.86₉ andc=24.13₈ Å;Z=3; 418 independent reflections;R=6.0%. The crystal structure consists of isolated [SiO₆] octahedra and [Si₂O₇] groups which are linked by [PO₄] tetrahedra forming a three-dimensional network. The average interatomic distances are: Si[6]?O=1.76₈, Si[4]?O=1.60₇ and P?O=1.52_i Å. The compound is isotypic with Ge₅O[PO₄]₆.     

Die Kristallstruktur von Ge5O[PO4]6

Zusammenfassung Die Kristallstruktur der Verbindung Ge₅O[PO₄]₆ wurde auf Grund dreidimensionaler Einkristalldaten ausWeissenberg-Aufnahmen ermittelt und nach der Methode der kleinsten Quadrate verfeinert: Raumgruppe ;a=7,994±0,004 undc=24,87±0,01 Å;Z=3; 467 unabhängige Reflexe;R=0,086.Die Kristallstruktur wird aus singulären [GeO₆]-Oktaedern und [Ge₂O₇]-Doppeltetraedern aufgebaut, die über [PO₄]-Tetraeder zu einem dreidimensionalen Strukturverband vernetzt sind. Die mittleren Abstände betragen: Ge^[6]–O=1,863, Ge^[4]–O=1,704 und P–O=1,525 Å.

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The crystal structure of Ge₅O[PO₄]₆

The crystal structure of Ge₅O[PO₄]₆ has been determined and refined by least-squares, using three-dimensional x-ray data fromWeissenberg-photographs: space group ;a=7.994±0.004 andc=24.87±0.01 Å;Z=3; 467 independent reflections;R=0.086.The crystal structure consists of isolated [GeO₆] octahedra and [Ge₂O₇] double tetrahedra which are linked by [PO₄] groups forming a three-dimensional network. The average interatomic distances are: Ge^[6]–O=1.863, Ge^[4]–O=1.704 and P–O=1.525 Å.

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