Intramolecular electrophilic aromatic substitution reactions of 2-amidoacroleins: a new method for the preparation of tetrahydroisoquinolines, tetrahydro-3-benzazepines, and hexahydro-3-benzazocines

[reaction: see text]. A variety of heterocyclic ring systems can be prepared by subjecting N-aryl-substituted 5-amido-1,3-dioxins to Lewis acids. The reactions proceed via catalyzed retrocycloadditions to afford 2-amidoacroleins and concomitant regioselective electrophilic aromatic substitution reactions. The transformation is also successful using dioxins with amides that are within the incipient ring to afford the analogous lactams.     

Total synthesis of (+/-)-perophoramidine

The first total synthesis of racemic perophoramidine is described. The key step features the highly stereoselective introduction of the vicinial quaternary centers via base-promoted carbon-carbon bond formation between a 3-alkylindole and a 3-bromo-3-alkylindolin-2-one. This transformation presumably proceeds through a conjugate addition or Diels-Alder cycloaddition of the 3-alkylindole with a 3-alkylindol-2-one intermediate.     

X-ray magnetic circular dichroism of Pseudomonas aeruginosa nickel(II) azurin

We show that X-ray magnetic circular dichroism (XMCD) can be employed to probe the oxidation states and other electronic structural features of nickel active sites in proteins. As a calibration standard, we have measured XMCD and X-ray absorption (XAS) spectra for the nickel(II) derivative of Pseudomonas aeruginosa azurin (NiAz). Our analysis of these spectra confirms that the electronic ground state of NiAz is high-spin (S = 1); we also find that the L(3)-centroid energy is 853.1(1) eV, the branching ratio is 0.722(4), and the magnetic moment is 1.9(4) mu(B). Density functional theory (DFT) calculations on model NiAz structures establish that orbitals 3d(x2-y2) and 3d(z2) are the two valence holes in the high-spin Ni(II) ground state, and in accord with the experimentally determined orbital magnetic moment, the DFT results also demonstrate that both holes are highly delocalized, with 3d(x2-y2) having much greater ligand character.     

用SN型催化剂合成苯乙烯一丙烯嵌段共聚物的研究──Ⅰ．聚合条件对共聚合反应的影响

用稀土化合物改性的钛系载体催化剂（ＳＮ催化剂）进行苯乙烯和丙烯顺序嵌段共聚合（Ｓｅｑｕｅｎｔｉａｌｂｌｏｃｋｃｏｐｏｌｙｍｅｒｉｚａｔｉｏｎ）的研究．考察了苯乙烯预聚时间、单体比、外加给电子体（ＥＢ）、烷基铝浓度、催化剂浓度和聚合温度等条件对共聚合的影响．发现外加酯（ＥＢ）降低了共聚合反应催化活性，在ＥＢ／Ｔｉ摩尔比为５范围内，外酯有助于提高嵌段共聚物（ｉＰＳ—ｂ—ｉＰＰ）中ＰＳ段和ＰＰ段的等规度及增加苯乙烯链节含量．ＳＮ型催化剂对苯乙烯一丙烯嵌段共聚合有较高的催化活性，催化效率在１００ｇ聚合物／ｇ－Ｔｉ以上．共聚物通过溶剂革取分级除去均聚物后，所得嵌段共聚物中苯乙烯链节含量可在１５～８５ｍｏｌ％之间调节．其结构表征续见第ＩＩ报．     

Zum radiogenen Argon in Eisenmeteoriten

Ohne Zusammenfassung     

Composition and properties of freeze-dried products of nicotinic acid withβ-cyclodextrin and heptakis (2,6-0-dimethyl)-β-cyclodextrin

The purpose of the study was to examine the formation of inclusion compounds in the freeze-dried products obtained from aqueous solutions of nicotinic acid and -cyclodextrin (-CD), or heptakis (2,6-0-dimethyl)--cyclodextrin (DIMEB). The molar ratios used were 1:1 and 2:1. In addition two freezing temperatures (–40 and –196°C) and different secondary drying temperatures (+50 and +80°C) were used. Freeze-dried products with -CD obtained after low temperature freezing are of the same crystallographic structure as seen in a pure inclusion compound prepared by coprecipitation. Amorphous products were formed after fast freezing. The molar ratios of included nicotinic acid in the freeze-dried products vary — dependent on the preparation conditions — between 0.75:1 and 1:1. A factorial design proves that the included drug amount can be increased by enhancement of the amount of nicotinic acid used, by faster freezing, and by the combination of these two factors. The proof of inclusion formation was given by a combination of X-ray diffractography, differential scanning calorimetry, thermogravimetry and thermofractography.The freeze-dried preparations obtained with DIMEB were amorphous mixtures of the two components. No proof for inclusion of the nicotinic acid in the cyclodextrin cavity could be given. Higher (–40°C) or lower (–196°C) freezing temperatures and the running of the secondary drying process could not influence these results. The very low stability constant of the complex and steric reasons are responsible for this behavior.     

Gruppenuniversalität und Homogenisierbarkeit

Summary For a classC of structures there are two archetypical questions: 1) Is every group G the full automorphism group of some C C? and 2) May every C C embedded into some homogeneous H C, i.e. into a structure H enjoying some transitivity properties? Using model theoretic language and conditions on the existence of certain free constructions withinC, some rather general positive answers to these questions are obtained. These abstract results give some (methodical) unification to a variety of theorems for some very concrete classesC of combinatorial, geometrical or algebraic nature in the literature. To underline this point, the major part of the paper is devoted to a systematic survey of classesC of structures in which our general approach is applicable, included many classesC for which our type of questions has not yet been considered.

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Unserem lieben FreundeAdriano Barlotti zum 60. Geburtstag gewidmet.

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Die Autoren danken herzlich der Deutschen Forschungsgemeinschaft für die gewährte Unterstützung; der erstgenannte Autor bedankt sich darüber hinaus beim Consiglio Nazionale delle Ricerche für ein Stipendium an der Universität Bologna.     

Multiply charged ions in the mass spectra of aromatics

The prominence of multiply charged molecular and fragment ions upon electron-impact in the mass spectrometer is proposed as an experimental, empirical indication of aromatic character. The effects of electron withdrawing and donating substituents on the production of multiply charged ions are considered and appearance potentials are noted for several species.     

Chemoselective construction of substituted conjugated dienes using an olefin cross-metathesis protocol

[Reaction: see text] Various substituted conjugated dienes have been made by olefin cross-metathesis. Using either electronic or steric "protection," one of the olefins of the conjugated diene was deactivated relative to the other for cross-metathesis. The reactions proceed with very high chemoselectivity and, when steric deactivation is used, very high diastereoselectivity.