Reaktionen mit phosphororganischen Verbindungen, 48. Mitt.

Reaction of the vicinal diols of steroids1, 5, 7, 10, 13, and16 with TPP/DEAD yields both regio-and stereospecifically the oxosteroids2, 6, 8, 11, 14, and15 by displacement of an axial hydrogen and extrusion ofTPPO besides the cholest-4-en-6-ols9 and12 and the cyclic carbonate3. 16, 17-androstandiol16 gives only the cyclic carbonate17. The different structures of the carbohydrates withcis-diol arrangement19 and21 lead exclusively to cyclic carbonates20 and22 in moderate yields. Treatment of1 with TPP/DEAD/HN₃ affords 3-azido-2-hydroxycholestane4 in addition to the above mentioned2.

     

The solvent extraction of Cu(II), Ni(II) and Co(II) with benzil mono(2-quinolyl)hydrazone

Benzil mono(2-quinolyl)hydrazone, BmQH, has been studied as an extracting agent for Cu(II), Ni(II) and Co(II). Though the uncomplexed ligand remains undissociated in the pH range 3.5-10, it can lose a proton on complexation with metals, owing to the electron-withdrawing effects of neighbouring groups. The dependence of degree of extraction on pH indicates that complexes of both Cu(2+) and Cu(OH)(+) are extracted. Cu(BmQH)(2) and Cu(OH)BmQH species are extracted into MIBK, and the Cu(OH)BmQH complex is extracted into benzene. In the vicinity of pH 5.5-6, extraction efficiencies greater than 95% can be achieved with both solvents. Both Ni(II) and Co(II) also show dependence of extraction on pH, but precipitation of both metals in the vicinity of pH 6 limits further studies.     

The asymmetric syntheses of the C-1 sidechains of zaragozic acid A and zaragozic acid C

The asymmetric syntheses of the C-1 sidechains of zaragozic acid A and C are described. Aldol reaction defines the chirality at C-4′and C-5′in two independent routes. Multigram preparation as well as a route amenable to derivatization are highlights of these approaches.     

Novel heteroleptic cis-(C--N)2Pd(II) chelates for the preparation of enantiopure planar chiral cyclopalladated 2-[tricarbonyl(eta6-phenyl)chromium]pyridine

In the presence of large amounts of [Me4N]Cl, the reaction of ortho-chloromercurated 2-[(eta6-phenyl)tricarbonylchromium]pyridine with mu-chloro cyclopalladated aromatic compounds yields a series of new heteroleptic heterodinuclear cis-(C--N)2Pd(II) complexes, which are valuable precursors of planar chiral cyclopalladated (eta6-arene)Cr(CO)3 complexes.     

Komplexometrische Bestimmung von Metallkationenverunreinigungen in Reinchemikalien

Zusammenfassung Ein Verfahren zur quantitativen summarischen Bestimmung von Metallionenverunreinigungen in flüssigen Chemikalien (Reinheitsprüfung) durch komplexometrische Titration mit photometrischer Endpunktsanzeige wird beschrieben. Als Indikator dient Eriochromschwarz T; erfaßbar ist zirka 1 g in 20 ml. Durch einfaches Einengen des Ausgangsmaterials lassen sich noch Metallionengehalte von 0,01 ppm mit einer Genauigkeit von einigen Prozent bestimmen.

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Summary A procedure is described for the quantitative summary determination of metal ion impurities in liquid chemicals (purity tests) through complexo-metric titration with photometric endpoint indication. Eriochrome black T serves as indicator. Approximately 1 g can be detected in 20 ml. Metal ion contents as low as 0.01 ppm can still be determined with a precision of several per cent by simple concentration of the starting material.

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Résumé On décrit un procédé de dosage total quantitatif des impuretés à l'état d'ions métalliques dans les produits chimiques liquides (contrôle de la pureté) par titrage complexométrique avec détection du point équivalent par photométrie. On utilise le noir ériochrome T comme indicateur. La limite de dilution est d'environ 1 g/20 ml. On peut encore doser des teneurs en ions métalliques de 0,01 ppm avec une erreur de quelques pour cent simplement en diminuant la quantité initiale de substance.

     

Synthesis of [ethylene-1-(eta(5)-4,5,6,7-tetrahydro-1-indenyl)-2- (eta(5)-4',5',6',7'-tetrahydro-2'-indenyl)]titanium dichloride, the elusive isomer of the Brintzinger-type ansa-titanocenes

We present a short synthesis of 1-(2-indenyl)-2-(3-indenyl)ethane (5) and a method for its conversion to the ansa-metallocene [ethylene(eta5-inden-1-yl)(eta5-inden-2-yl)]titanium dichloride (13). The synthetic strategy applied to prepare bisindene 5 relies on the efficient alkylation of 2-(phenylsulfonyl)indane followed by HMPA-assisted E1cB-elimination of phenylsulfinate. This tandem sequence circumvents the predisposition of indene to undergo C(1)-alkylation and enables access to C(2)-substituted indenes. The key step in the synthesis of the title ansa-titanocene (4) features a previously unreported equilibration step to generate the bis(indenide anion) of 5. Complexation with TiCl4.(THF)2 followed by hydrogenation of the product metallocene furnishes ansa-titanocene 4.     

Elektronenlokalisierung im Grundzustand und in angeregten Zuständen Pars-Orbital-Methode, 12. Mitt

UsingGleason's theorem the pars orbital concept is developed for excited states of conjugated systems described by CI-methods. A significance index is introduced to evaluate different patterns of fragmentation. The usefulness of this approach is illustrated for butadiene, biphenyl, naphthalene, and azulene.

11. Mitt.:H. Karpf, O. E. Polansky undM. Zander, Tetrahedron Lett.1978, 2069.     

The pH dependence of phenolphthalein: A 13c NMR study

The pH dependence of the ¹³C NMR spectra of phenolphthalein has been measured and interpreted. The spectrum of the neutral compound 1 is compared with the spectra of the dianion 4, the trianion5 and the carbocation7. At the first time spectroscopic evidence for the carbinol 6 is given.     

Enzymatic hydrolysis of heterocyclic nitriles

Chemoselective hydrolysis of heterocyclic nitriles can be achieved by an easy to use immobilized biocatalyst prepared from Rhodococcus sp. Pyrimidine-2-carbonitrile ( 2a ) and 3-chloropyridazine-4-carbonitrile ( 4a ) were converted into the corresponding amides while from 2-ethoxycarbonyl-4-pyridinecarbonitrile ( 1a ), 6-methylpyridazine-3-carbonitrile ( 3a ), 3-chloropyridazine-4-carbonitrile ( 4a ), 3-ethoxycarbonyl-4,5-dihydroisoxazole-5-carbonitrile ( 8a ), indole-3-carbonitrile ( 9a ) and indole-3-ylacetonitrile ( 10a ) the acids were formed.