Synthesis and aromatic nucleophilic N-N, N-S and N-O exchange reactions of N,N-dimethyl-2-trifluoroacetyl-1-naphthylamine

We succeeded in the synthesis of N,N-dimethyl-2-trifluoroacetyl-1-naphthylamine (10) by the regioselective deacylation of N,N-dimethyl-2,4-bis(trifluoroacetyl)-1-naphthylamine with trifluoroacetic acid and water. The aromatic nucleophilic substitutions of 10 with various amines, thiols and alcohols proceeded cleanly to give the corresponding N-N, N-S and N-O exchanged products in moderate to excellent yields.     

Interaction second virial coefficients at low temperatures for NeKr and NeO2 systems

Published results of vapour—liquid and vapour—solid equilibrium studies for neon—krypton and neon—oxygen mixtures have been analysed to give values for the interaction second virial coefficients. B₁₂. Comparisons are made with other results for the NeKr system and with the predictions of some proposed intermolecular potentials.     

The Crystal Structure of Ba58Ga22F180O

The crystal structure of Ba₅₈Ga₂₂F₁₈₀O is established by means of X‐ray single crystal diffraction. It is tetragonal: a = 22.033(1) Å, c = 17.626(1) Å, Z = 2. The structure is solved in the space group I4/mmm (n° 139), using 3219 independent reflections. It is mainly built from a deficient arrangement of fluorite‐type [FBa₄] tetrahedra connected by edges and vertices which constitutes the skeleton of the structure, giving rise to large cavities in which lie isolated fluorine ions in tetrahedral and octahedral barium environment, isolated [F₂Ba₆] bitetrahedra, isolated barium ions in eight‐coordination of fluorine and a complex arrangement of isolated [GaF₆] octahedra and isolated [Ga₂F₁₀O] bioctahedra.     

Structure électronique des éthers vinylique et divinylique: Introduction de la déformation des orbitales σ

Résumé La théorie L.C.A.O. améliorée est appliquée à l'étude des éthers vinylique et divinylique. La grande différence d'électronégativité entre les orbitales atomiques entrant dans la liaison entre l'oxygène et le carbone nous a conduits à introduire la déformation réciproque de ces orbitales. Les énergies calculées pour la première transition N V, 6,5 et 6,3 eV, sont en excellent accord avec l'expérience.

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The improved L.C.A.O. theory is applied to the vinyl and divinyl ethers. The large differences of electronegativity between the atomic orbitals which enter the-bond between oxygen and carbon led us to the introduction of the mutual deformation of these orbitals. The calculated energies for the first N V transition, 6,5 and 6,3 eV are in excellent agreement with experiment.

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Zusammenfassung Die verbesserte L.C.A.O.-Theorie wird auf Vinyl- und Divinyläther angewandt. Die große Elektronegativitätsdifferenz zwischen den an der-Bindung zwischen Sauerstoff und Kohlenstoff beteiligten Atomzuständen hat uns veranlaßt, die gegenseitige Deformation dieser Zustände einzuführen. Die für die erste N V-Elektronenbande berechneten Energien, 6,5 und 6,3 eV, stimmen ausgezeichnet mit der Erfahrung überein.

     

Recent Trends in Photoaffinity Labeling

Investigation of receptor—ligand interactions remains an inexhaustible challenge for chemists and biologists. Structural exploration of biological receptors is the starting point for a better understanding of how they function. Photoaffinity labeling is a biochemical approach to identify and characterize receptors targeting further structural investigations. The primary structure of a receptor protein was typically obtained by reverse genetics after exhaustive purification and sequencing of the N-terminal peptide, which allowed the design of the corresponding oligonucleotide probes. Synthesis of these oligonucleotide probes then led to identification of cDNA clones by hybridization. Following this strategy, several membrane neurotransmitter receptors and constituent polypeptides, present in very small quantities in the central nervous system, were identified and their sequence deduced from the cDNA sequence. Since photoaffinity labeling implies the formation of a covalent bond between a radiolabeled ligand analogue and a receptor binding site, it becomes theoretically possible to isolate and sequence radiolabeled peptides and then synthesize the corresponding oligonucleotide probes. Photoaffinity labeling might avoid the critical solubilization and purification steps of the classical approach. To our knowledge, no such example of primary structure determination based on photoaffinity labeling experiments has been reported. However, the extraordinary developments in gene cloning technologies, in particular homology cloning and expression cloning, have made this approach obsolete and raised the question of new perspectives for photoaffinity labeling technology. In this article we present an update on selected original developments, as well as new challenges for this method. Photoaffinity labeling not only gives access to structural elements but is also a potential tool for the investigation of functional aspects of biological receptors, for example their role in signal transduction mechanisms.     

Enzymic control of stereochemistry among the Thalictrum bisbenzylisoquinoline alkaloids

The new bisbenzylisoquinolines (+)-tha1igrisine $\text{1}$ and (+)-tha1iphylline ($\text{6}$) have been isolated from $\text{Thalictrum minus}$ var. $\text{microphyllum}$. Four rules are described which correlate the structures of Thalictrum bisbenzylisoquinolines with their stereochemistry at C-1 and C-1'. As a result, (+)-tha1rugosamine is shown to be identical with (+)-homoaromo1ine ($\text{14}$). (+)-Thalisamine and (+)-N'-norhernandezine are also identical and are represented by expression $\text{18}$. The sole exception to the rules is (-)-isothalidezine ($\text{15}$).     

Direct colorimetric determination of small amounts of tungsten in titanium

There is need for a rapid and accurate method for the determination of small amounts of tungsten in titanium. In this paper a direct colorimetric method is proposed for the determination of tungsten in titanium that is applicable to the range of 0.005 to 0.3 per cent. tungsten. The sample is dissolved in hydrochloric acid and the titanium and tungsten reduced with metallic zinc. Thiocyanate is added and the yellow color read at 410 millimicrons with a spectrophotometer. A study was made of the best conditions for developing the color, including the effect of varying amounts of titanium, thiocyanate and hydrochloric acid. An investigation was made to determine the proper wave length for reading the color, the stability of the color and effect of interferences.     

Fluorinated hydrazones. Part 1: Reductive coupling reactions of chlorodifluoroacetylated dialkylhydrazones using tetrakis(dimethylamino)ethylene (TDAE)

A series of new α-diketone derived gem-difluorinated mono-hydrazone derivatives are easily obtained in moderate to good yields from the tetrakis(dimethylamino)ethylene-mediated reductive coupling reactions of chlorodifluoroacetylated dialkylhydrazones with aromatic aldehydes, ethyl pyruvate and an N-tosyl aldimine.     

X-ray photoelectron emission studies of mixed selenides AgGaSe2 and Ag9GaSe6

Auger and direct electron specta from crystalline AgGaSe₂ and Ag₉GaSe₆ have been studied with X-ray photoelectron spectroscopy. It is shown that the AgM₅N_4,5N_4,5 and M₄N_4,5N_4,5 Auger spectra are more sensitive to the chemical environment than the Ag 3d direct photoelectron spectra. Furthermore the Auger parameter as defined by Wagner is used in order to characterize the chemical state of these compounds. Last, the XPS spectra of the valence-band region are investigated and chalcogen s and p and noble-metal d bands are clearly identified. The electronic structure of these two selenides does not seem to be determined predominantly by the crystal structure. As a whole, the spectral features are discussed in connection with the character of the chemical bonding and the physical properties of these compounds.     

The indenobenzazepine-spirobenzylisoquinoline rearrangement; stereocontrolled syntheses of (±)-raddeanine and (±)-yenhusomine

Stereoselective rearrangement of indenobenzazepine cis ketols $\text{2}$ and $\text{5}$ with TPAA in pyridine produces spirobenzylisoquinolines $\text{3}$ and $\text{6}$, respectively. The latter product is also obtained by rearrangement of trans ketol $\text{7}$. The transformation of ketols $\text{5}$ and $\text{7}$ must, therefore, proceed through the intermediacy of aziridinium cation $\text{9}$. A similar process obtains in the transformation of $\text{2}$ to $\text{3}$. NaBH₄ reduction of $\text{3}$ gives (±)-raddeanine ($\text{4}$). Rearrangement of diol $\text{10}$ supplies $\text{4}$ directly. (±)-Yenhusomine ($\text{13}$) is obtained from the reamangement of either diol, $\text{11}$ or $\text{12}$. In like fashion, diols $\text{14}$ and $\text{15}$ supply spirobenzylisoquinoline $\text{17}$.