Eine neue selektive Tüpfelreaktion auf organische Disulfide

Zusammenfassung Alphatische und aromatische Disulfide und Diselenide werden selektiv durch Nickel-Aluminiumlegierung (50/50) in salzsaurem Alkohol zu Thiolen bzw. Selenolen reduziert, die ihrerseits mittels der Jodazidreaktion nachgewiesen werden können. Dies ermöglicht einen selektiven Nachweis von Disulfiden bei Abwesenheit anderer mit Jodazidlösung positiv reagierender Verbindungen (Thiole, Thione, Senföle, Thiosäuren und Derivate).

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Summary Aliphatic and aromatic disulfides and diselenides are reduced selectively by nickel-aluminium alloys (50/50) in hydrochloric acid-alcohol to yield thiols or selenols, which in their turn can be detected through the iodine-azide reaction. This permits a selective detection of disulfides in the absence of other compounds which react positively with the iodine-azide solution (thiols, thiones, mustard oils, thio acids, and derivatives).

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Résumé L'alliage nickel-aluminium (50/50), dans le mélange alcool-acide chlor — hydrique, permet de réduire sélectivement les bisulfures et les biséléniures aliphatiques et aromatiques, en thiols ou en sélénols que l'on peut alors caractériser par la réaction à l'iode-azoture. Ceci rend possible une recherche sélective des bisulfures en l'absence d'autres composés donnant une réaction positive avec la solution à l'iode-azoture (thiols, thiones, essences de moutarde, acides du soufre et dérivés).

     

Nachweis und Bestimmung des Eisens und seine Trennung von anderen Elementen

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Kapazitäten und obere Einhüllende von Maßen

Ohne Zusammenfassung     

Multifunctional and reactive enantiopure organometallic helicenes: tuning chiroptical properties by structural variations of mono- and bis(platinahelicene)s

Acetylacetonato-platina[6]- and -platina[7]helicenes have been prepared from 2-pyridyl-substituted benzophenanthrene ligands by following a two-step cycloplatination reaction. The photophysical properties (UV-visible absorption and emission behavior) and chiroptical properties (circular dichroism and molar rotation) of the resolved enantiomers have been measured. These metallahelicenes constitute a novel family of easily accessible helicene derivatives that exhibit large and tuneable chiroptical properties that can be rationalized theoretically and compared to the parent [6]- and [7]carbohelicenes. Furthermore, they are red phosphors at room temperature and their large chiroptical properties can be modulated by oxidation of the metal center to Pt(IV). Hetero- and homochiral diastereomeric bis(metallahelicene)s that possess a rare Pt(III)-Pt(III) scaffold bridged by benzoato ligands have also been prepared. It is shown that the heterochiral (P,M)-bis(Pt(III)-[6]helicene) 9a(1) can isomerize into the homochiral (P,P)- and (M,M)-bis(Pt(III)-[6]helicene) 9a(2). Spectral assignments and an analysis of the optical rotation of these systems were made with the help of time-dependent density functional theory. The calculations highlight the contributions of the metal centers to the chiroptical properties. For 9a(1) and 9a(2), σ-π conjugation between the helicenes and the Pt-Pt moiety may contribute strongly to the optical rotation and electronic circular dichroism.     

Sustainable synthesis and automated deposition: an accessible discovery screening library of fragment-like purines

A sub-library of 88 information-rich lead-like purine derivatives were prepared and deposited in an open access academic screening facility. The rationale for the synthesis of these rigid low complexity structures was the privileged character of the purine heterocycle associated with its inherent probability of interactions with multiple adenine-related targets. Although generally expected to be weak binders in many assays, such fragment-like compounds are estimated to match diverse binding sites. It is suggested that heterocycles with many anchor points for hydrogen bonds can be anticipated to undergo very specific interactions to produce more negative enthalpies and thus provide superior starting points for lead optimization than compounds that owe their activity to entropic effects. The in vitro cytotoxicity of the small compounds on a panel of human cancer cell lines has been investigated and some of them showed marked unselective or selective toxicity. This data may be useful if these fragments are to be incorporated into drug-like structures via metabolically cleavable connections. The sub-library will be implemented as part of the ChemBioNet ( www.chembionet.info ) library, and it is open to screening campaigns of academic research groups striving for a fragment-based approach in their biological assays.