硫氰酸盐树脂相分光光度法测微量铁(Ⅲ)

本文介绍了硫氰酸根与铁（Ⅲ）在有表面活性剂Tweet-80存在下生成络阴离子吸附于强磁性阴离子树脂．富集于树脂相上的有色络合物可进行树脂相分光光度测定．比水相测定灵敏度提高10倍，ε4900力8．4×104L·mol-1’·cm-1选择性也好于水相测定、铁（Ⅲ）含量在0～1．28mg／L范围内服从Beer定律。用此法测定天然水、马奶酒等样品中微量铁（Ⅲ），结果令人满意。     

New efficient construction of the ABC core of the taxoids via a sequence of consecutive cobalt(I)-mediated [2 + 2 + 2] and [4 + 2] cyclizations

[reaction: see text] A new and efficient sequence of two consecutive cyclizations, a cobalt(I)-mediated [2 + 2 + 2] cyclotrimerization and a Diels-Alder reaction, is proposed to allow the formation of the ABC core of the taxoids in 65% overall yield, starting from an acyclic polyunsaturated precursor.     

Synthese,Kristallstruktur und Konformation von N2-Dibenzyl-N1-t-butoxycarbonylhydrazin

Summary The synthesis and the crystal structure of N²-dibenzyl-N¹-butoxycarbonyl hydrazine are reported. The compound was prepared from commercially availablet-butyl carbazate. It crystallizes in the triclinic space group P 1 witha=5.479(1) Å,b=9.559(1) Å,c=9.748(1) Å,a=63.81(1)°, =87.52(1)°, =74.07(1) Å,Z=1,D=1.18 g/cm³. The structure was solved by direct methods and refined toR=0.0329.

     

Reaktion der α, γ, δ, ζ-Tetraketone mit Selentetrachlorid und Schwefeldichlorid

Zusammenfassung , , , -Tetraketone (1) reagieren in der Dienolform (2) mit Bleitetraacetat², Selendioxid³, Selentetrachlorid und Schwefeldichlorid. Hauptprodukt der Reaktion mit SeCl₄, ist 2,5-Diacyl-3,4-dihydroxyselenophen (10), mit SCl₂, 2,5-Diacyl-3,4-dihydroxythiophen (11). Es wird die Synthese einer Reihe von Verbindungen der Struktur1, 10 und11 beschrieben.

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, , , -Tetraketones (1) react in dienolic form (2) with lead tetraacetate², selenium dioxide³, selenium tetrachloride and sulphur dichloride. The main product of the reaction with SeCl₄ is 2,5-diacyl-3,4-dihydroxyselenophene (10), and with SCl₂ 2,5-diacyl-3,4-dihydroxy-thiophene (11). A series of compounds with the structures1, 10, and11 is described.

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Herrn Prof. Dr.F. Wessely zum 70. Geburtstag freundlichst zugeeignet.     

Proton-proton and deuteron-deuteron correlations in interactions of relativistic helium nuclei with protons

The reactions⁴Hep pp+X,³Hep pp+X and⁴Hep ddp have been investigated and the correlation function has been measured for protons and deuterons with small relative momenta. Strong positive correlation has been observed for protons related mainly to the final state interactions in¹S₀ state. The root mean square radius of the proton source calculated from the correlation function has been found to be equal to (1.7±0.3) fm and (2.1±0.3) fm for⁴He and³He respectively. It agrees with the known radii of these nuclei.We would like to thank Dr R. Lednicky for discussion, helpful suggestions and for making available the computer program that calculates the theoreticalpp correlation function. The authors also thank Dr D.H. Boal for providing the results of the two-deuteron correlation function calculations.     

Simple approach to "locked" chlorins

[reaction: see text] A novel synthetic approach to diversely functionalized "locked" chlorins is described. A suitably substituted 2,5-diformylpyrrole undergoes the macrocyclization reaction with tripyrranes, thereby generating porphyrins. Upon the reaction with 1,3-dipoles these porphyrins regioselectively furnish pyrrolidine-fused chlorins, which cannot oxidize to the corresponding porphyrins. In the process involving just six steps from commercially available and cheap materials we are able to obtain approximately 200 mg of pure stable chlorins (the overall yield is 1.5-2.8%).     

Complexometric catalytic titrations using the indicator reaction periodate-triethanolamine

The possibility of applying a new indicator reaction, i.e., periodate-triethanolamine, as the indicator in titrations of ethylenediamine-N,N,N′,N′-tetracetic acid (EDTA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), and diethylenetriaminepentaacetic acid (DTPA) with standard manganese(II) sulfate solution (phosphate buffer pH 6.84) has been investigated. The titration course was followed potentiometrically using a perchlorate ion-selective electrode. The optimum conditions for determinations in relation to concentration of the indicator reaction components have been established. Furthermore, the influence of some ions on the possibility of EDTA determination was considered and maximally tolerable concentrations under these conditions were established. The amounts of 0.170–18.00 mg of EDTA, 0.150–16.00 mg of DCTA, and 0.180–19.00 mg of DTPA were determined with a maximal relative standard deviation less than 1.0%. Results are in good agreement with those of comparable methods. Finally, the experimental catalytic titration curves obtained in this way are compared to the simulated ones.     

Electrochemical recognition of cations by bis(pyrrolo)tetrathiafulvalene macrocycles

[structure: see text] Tetrathiafulvalene redox-responsive ligands devoid of cis/trans isomerism containing the electroactive bis(pyrrolo[3,4-d])tetrathiafulvalene moiety and polyether subunits have been synthesized. One ligand exhibits high binding affinities for Pb2+ and Ba2+ cations as shown by independent methods (1H NMR, UV-vis spectroscopy, and cyclic voltammetry). The ability of this receptor to electrochemically recognize Pb2+ and Ba2+ is shown by cyclic voltammetry.     

Fenestranes in Synthesis: Unique and Highly Inspiring Scaffolds

The scaffold of fenestranes is quite unique, as it contains four condensed cycles and a distorted tetracoordinated central carbon atom with bond angles greater than the regular 109°28“. In this Minireview, a detailed overview on the developments regarding this compound class, including their synthesis, is given for the time period since 2006. In the past years, natural products that belong to the class of heterofenestranes have been isolated and their syntheses will also be discussed.     

The sum of two S-units being a perfect power in global function fields

Let x ₁ and x ₂ be integers divisible only by some fixed primes. Is it possible that x ₁+x ₂ is a perfect power? Special cases of the equation x ₁+x ₂ = y ^k were formerly considered over ?. In this paper we develop an algorithm to solve this equation over global algebraic function fields. Our method is illustrated by two explicit examples.