Beiträge zur Chemie der Pyrrolpigmente, 70. Mitt.: Zum aktiven Transport mit tripyrrinoiden Liganden

The tripyrrin carboxylic acid6 exhibits a pronounced efficiency for carrier mediated proton driven secondary active transport (counter transport) for a series of toxic or valuable cations in a bulk chloroform membrane. In case of Zn⁺⁺ ions the mechanism including complete concentration profiles forNerst diffusion layers and bulk phase have been established. This compound might be used for detoxification or enrichment of precious metals using membrane separation systems.

Herrn Prof. Dr.A. Neckel mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Die Fehlordnung des Natriumazides und deren Einfluß auf die thermische Zersetzung, 4. Mitt.: Über die Programmierung von Zersetzungsreaktionen mit Hilfe von Korngrößenverteilungen

It is shown that in the case of thermal decomposition of sodium azide the overall kinetics can be predicted by defined particle size of the decomposed sodium azide crystals. This is always the case if the rate constant is a function of the particle size. Hence this special example can be generalized for similar decomposition reactions. It is necessary that the particles decompose independently which could be proved experimentally with sodium azide. If for this reason we state for true that the pressure/time-function of each particle size add together it is possible to set up a formula for the pressure/time-function of any particle size distribution. With the pressure/time function holding for sodium azide of uniform particle size, the total function for a Gauß distribution can be calculated exactly. Moreover, the trivial case of one single particle size and the case of two different particle sizes are discussed. Furthermore an approximation method for any arbitrary pressure/time-functions and distribution by means of “Schwerpunktdeutung” are discussed which can be carried out graphically as well as numerically. The numerical approximation is illustrated by an example. Pressure/time-functions then loose their characteristic form because of their dependence on the particle size distributions under consideration. In this case, reaction mechanism cannot be derived from pressure/time functions.     

Branched Star-Type Polysilyllithium Compounds: The Effects of beta-Silyl Substitution and of Complexation on Their Molecular Structure

No Abstract     

Reaktionen an komplexgebundenen liganden: XXXVI. Synthese und oxidationsverhalten von M(CO)5-komplexen (M = Cr,Mo, W) mit amin- und benzochinondiimin-liganden

The oxidation of yellow Cr(CO)₅NH₂R complexes (NH₂R = aniline, m-toluidine, 3,5-xylidine, m-anisidine) with Pbac₄ gives deep blue to deep purple coloured compounds, which have been identified as the respective [Cr(CO)₅(N-phenyl-1,4-benzochinon-diimine)] complexes. Oxidation of the p-phenylenediamine complex yields [(OC)₅CrHNC₆H₄NHCr(CO)₅], which is also deep blue. The binuclear blue complex [{Cr(CO)₅}₂HNC₆H₄NC₆H₅] is obtained by treating Cr(CO)₅THF with the free ligand in THF/hexane; it dissociates rapidly in acetone to form [Cr(CO)₅HNC₆H₄NC₆H₅] and Cr(CO)₅. Analogous Mo(CO)₅ and W(CO)₅ complexes could not be obtained. The oxidation of [W(CO)₅(m-anisidine)] by I₂ yields [W(CO)₄I]₂. All the compounds were characterized by spectroscopic methods as well as by elemental analysis.     

The mass spectra of TMS-ethers of deuterated polyalcohols. A contribution to the structural investigation of sugars

Aldoses, ketoses, deoxy-aldoses, deoxy-keto-aldoses, lactones, deoxy-lactones and other similar compounds are readily reduced by NaBD₄ to the corresponding polyalcohol. Their trimethylsilyl ethers show characteristic mass spectra which allow firm assignments of the position of deuteration and hence of the nature of the starting sugar compound. The g.c./m.s. coupling technique even allows trace analysis since full information can be derived from the most intense fragments of the mass spectra.     

Intramolekulare Cyclisierung von Aminofluorsilanen

Aminofluorosilanes react with lithiated amines undergoing LiF-elimination and substitution (1). The acyclic silicon-nitrogen-compound2 is isolated in the reaction with a difluorosilane after renewed lithiation.2 is cyclisated in the reaction with butyllithium by butane- and LiF-elimination (3). Aminofluorosilanes with bulky (4) or mesomeric stabilized (5) ligands form stable lithioaminofluorosilanes, which react with fluorosilanes giving substitution products (6, 7).6 and7 react with the lithium salt oftert-butylamin in a molar ratio of 12 to give8 and9 by intramolecular cyclisation.—The mass,¹H and¹⁹F nmr spectra of the compounds are reported.     

Synthesis of Naturally Occurring Pyrazine and Imidazole Alkaloids from Botryllus LeachiRID=”a”ID=”a”?Dedicated to Prof. G. M?rkl on the occasion of his 75th birthday

The synthesis of the naturally occurring and biologically active alkaloids 1 and 2, first isolated from the red ascidian Botryllus leachi by Duran et al. [1], is described and the structure proposed for Botryllazine B (1) is confirmed. The analytical data for 2-(p-hydroxybenzoyl)-4-(p-hydroxyphenyl)imidazole (2) are discussed and compared with the literature. With special emphasis of ¹H NMR data the tautomerism of aroylimidazolemethanones is described.     

Syntheses of (+)-(S,S)-(cis-6-Methyltetrahydropyran-2-yl)acetic acid and of (−)-(R,R)-Didesoxy-pyrenophorine Using a New d5-Reagent. Preliminary communication

The Li/K-derivative 6 is used to synthesize the title compounds ( 3a and 4a ) in enantiomerically pure form from (?)-(S)-propylene epoxide. The C,C bond forming key step leading to the hydroxyketone 7 is followed by cyclization (→, 8 ), Beckmann cleavage (→ 9b ) and hydrolysis to 3a (recently isolated from civet). Base treatment of 3a opens the ring ( 10 ) to give the hydroxyacid 1 which is cyclized to the macrolide 4a . The synthetic usefulness of the highly nucleophilic doubly reduced dienone system 6 as d⁵-reagent (see synthons 2) is thus demonstirated.     

A convenient synthesis of 4-aminoaryl substituted cyclic imides

An efficient one-step synthesis of 4-nitro-N-aryl substituted glutarimides, succinimides and maleimides in polyphosphoric acid is described together with the subsequent reduction to the corresponding anilines. The scope and limitation of this cyclocondensation are presented.