Synthetische Verwendung von Epoxynitronen. II. Synthese von Steroid-α-methyliden-γ-lactonen

Synthetic application of epoxynitrones. II. Syntheses of steroidal α-methylidene-γ-lactones This communication describes the application of the epoxynitrone/CF₃SO₃SiR₃ → 1,2-oxazine annelation-reaction [1] to the syntheses of steroidal α-methylidene-γ-lactones from olefines, e.g. 12 → 14a/b → 16a/b → 18a/b → 20 → 22 (Scheme 2).     

α-Chlor-nitrone IV: Zur Stereochemie der λ-Lacton-Synthese und eine Methode zum Aufbau von α-Methyliden-λ-lactonen aus Olefinen. Über synthetische Methoden, 8. (vorläufige) Mitteilung

The Ag⁺-induced reaction between N-cyclohexyl-α-chloro-propionaldonitrone and the two diastereomeric 2-butenes in liquid SO₂ is a stereospecific cis-addition. The use of N-cyclo-hexyl-α,β-dichloro-propionaldonitrone in this type of reaction provides a preparative route from olefines to α-methylidene-butyrolactones.     

α-Chlor-nitrone II: Eine Methode zur Darstellung von γ-Lactonen aus Olefinen. Über synthetische Methoden, 6. (vorläufige) Mitteilung

The addition products obtained by the Ag⁺-induced reaction of α-chloro-aldonitrones with olefins (see preceding communication) can be utilized efficiently for making γ-lactones (see scheme 1).     

2,2′-Dichinoxalyl — ein neues Reagens zur spektrophotometrischen Bestimmung von Titan(III)

Zusammenfassung 2,2-Dichinoxalyl ist ein geeignetes Reagens zur spektrophotometrischen Bestimmung von Titan(III) in salzsaurem Medium. Das molare Verhältnis der Reaktionspartner 2,2-DChx: Ti(III) beträgt 1 2. Die bei der Redoxreaktion entstehende blaue Verbindung weist ein Absorptionsmaximum bei 680 nm auf. Der molare Extinktionskoeffizient beträgt =2,9·10⁴. Im Ti (III)-Konzentrationsbereich von 2,09 · 10^–6 bis 1,04 · 10^–4 erhält man eine geradlinige Eichkurve. Die beschriebene Methode eignet sich zur Bestimmung von Titan in Ilmeniten und Titanlegierungen. 2,2-DChx kann auch zur extraktions-kolorimetrischen Bestimmung von Ti(III) verwendet werden.

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2,2-Diquinoxalyl — A new reagent for spectrophotometric determination of titanium(III)

Summary 2,2-Diquinoxalyl (DQux) is a suitable reagent for spectrophotometric determination of titanium (III) in HCl medium. The molar relationship of the reaction partners DQux Ti(III) is 12. The blue compound arising in the redox reaction exhibits an absorption maximum at 680 nm. The absorptivity is =2.9×10⁴. In the Ti(III) concentration range from 2.9×10^–6 to 1.04×10^–4 a straight-line calibration curve is obtained. The method described is suitable for determination of titanium in ilmenites and titanium alloys. DQux can also be used for extraction colorimetric determination of Ti(III).

     

Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6-Oxo-isophoron. II. Ein neues Konzept für die Synthese von (3RS, 3′RS)-Astaxanthin

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6-Oxo-isophorone. II. A Novel Concept for the Synthesis of (3RS, 3′RS)-Astaxanthin Starting from 6-oxo-isophorone ( 2 ) a new concept for a seven-step synthesis of (3RS, 3′RS)-astaxanthin ( 1 ) has been developed. As a key feature of the new approach, the oxidation state of astaxanthin ( 1 ) is adjusted already at an early stage of the synthesis. Thus, manipulation on more complex intermediates later in the synthesis is reduced to a minimum. Acetonide 10 or dimer 13 represent the key intermediates of this concept (Scheme 2). The whole sequence has been run on a kg scale with an overall yield of 52% (s. Scheme 5).     

p-(5-Fluor-2,4-dinitro-1-phenylazo)-N,N-dimethylanilin,ein neues Reagens zur flüssigchromatographischen Bestimmung von Phenolen

The synthesis ofp-(5-fluoro-2,4-dinitro-1-phenylazo)-N,N-dimethylaniline and its reactions with phenoles top-(2,4-dinitro-5-phenoxy-1-phenylazo)-N,N-dimethylanilines and the use of the resulting coloured products for the TLC determination of phenoles is described.