Reexamination of the thermolytic rearrangement of 4-halophenyl azides to 2-aminophenols and other products

Summary The halogenation of derivatives of 2-aminophenol with N-chloro- and N-bromosuccinimides at ambient temperatures in acetic acid was studied. With the necessary compounds available, a reexamination of the thermolytic rearrangement of 2-halophenyl azides to 2-aminophenols and other products was undertaken. It is certain that the rearrangement of 4-halophenyl azides to 2-aminophenols occurs but the products identified in this study differ significantly from those reported previously by Suschitzky et al. (1963, 1966).

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Neuuntersuchung der thermolytischen Umlagerung von 4-Halogenphenylaziden zu 2-Aminophenolen und anderen Produkten

Zusammenfassung Es wurde die Halogenierung von 2-Aminophenol-Derivaten mit N-Chlor- und N-Bromsuccinimid bei Raumtemperatur in Essigsäure untersucht. Mit den zur Verfügung stehenden Verbindungen konnte eine Neuuntersuchung der thermolytischen Umlagerung von 4-Halogenphenylaziden zu 2-Aminophenolen und anderen Produkten unternommen werden. Diese Umlagerung findet sicherlich statt, allerdings differieren die dabei beobachteten Produkte signifikant von denen, die Suschitzky et al. 1963 und 1966 beschrieben.

     

Use of participant EQA results to assess sample homogeneity and stability for qualitative analytes

International requirements for PT and EQA state that providers must demonstrate that samples are homogeneous and stable. However, testing for homogeneity and stability can be expensive, use samples that could otherwise serve as quality-control materials, and can also fail to detect significant inhomogeneity and instability. In some situations it may be preferable to use the results from participants to identify problems with sample lots, if historic results follow predictable distributions and a statistical decision rule can be produced. An unusually high proportion of incorrect results may indicate that samples were inhomogeneous or unstable. Conditions under which this can be demonstrated are discussed, and the efficacy of the proposal is demonstrated with two examples. This procedure is especially effective when there are a large number of participants and/or a historic small proportion of incorrect results. Providers who adopt this proposal will need to retain samples for testing and assume the risk of distributing bad samples.Presented at the Eurachem PT Workshop September 2005, Portorož, Slovenia     

New Ba5M5−xPtxClO13 (M=Fe, Co) oxychlorides with layered perovskite-related structure

Crystals of Ba₅Fe_5−xPt_xClO₁₃ and Ba₅Co_5−yPt_yClO₁₃ were prepared for x=1.31, 1.51, 1.57, 1.59 and y=0, 0.97 and 1.08 in a BaCl₂ flux and investigated by X-ray diffraction methods. These compounds adopt a 10H perovskite structure built from the stacking of BaO₃ and BaOCl layers in the sequence (BaO₃)₄(BaOCl) with space group P6₃/mmc. The cation sites within the trimeric unit of face-sharing octahedra are occupied by Co or Fe and Pt ions, while the tetrahedral sites formed between BaO₃ and BaOCl layers are only occupied by Fe or Co. Moreover, oxygen stoichiometry indicates an average oxidation state for Co and Fe higher than +III, indicating the stabilization of Co⁴⁺ and Fe⁴⁺.     

Magnetic resonance studies of the deuteration effect on intersystem crossing in the anthracene molecule

The intersystem crossing decay constants from the ³B_2u state into the ground state of anthracene-d₁₀ in a phenazine crystal have been determined by magnetic resonance techniques at 1.5°K both at high magnetic field and, by a parameterization procedure, at zero magnetic field. A comparison of the anthracene-d₁₀ zero-field results with those for anthracene-h₁₀ show the effects of deuterium substitution to be largest for the in-plane spin levels of the anthracene triplet state.     

Synthesis and antifolate activity of 8,10-dideazaminopterin

A synthesis of 8,10-dideazaminopterin, using 2,4-diamino-6-bromomethyl-8-deazapteridine ( 2 ) as a key intermediate, is described. Condensation of the triphenylphosphinylide derived from 2 with p-formylbenzoyl-L-glutamate afforded a 9,10-dehydro-8,10-dideazaminopterin ester intermediate 5 . Hydrogenation of the olefinic linkage and subsequent hydrolysis of the glutamate ester gave the title compound. 8,10-Dideazaminopterin was a potent growth inhibitor of folate dependent bacteria. It was 16 times more potent then methotrexate as an inhibitor of dihydrofolate reductase derived from L1210 leukemia cells, and showed strong activity against L1210 in mice.