Synthesis of thienothiazocinoisoindolediones and thienothiazinoisoindolones from mercaptothiophenes and chloromethylphthalimide

2-Thienylthiomethylphthalimides 3a,b were synthesized by action of Chloromethylphthalimide on 2-or 3-mercaptothiophene. Reduction of 3a,b and Wittig reaction using carbethoxycarbonyltriphenyl-phosphorane gave the corresponding acetic acids 5a,b which cyclized under Friedel and Crafts conditions to lead the thienothiazocinoisoindolediones 6a,b. Thienothiazinoisoindolones 7a,b were obtained from hydroxyisoindolones derivatives 4a,b in acid conditions via an acyliminium ion.     

Anderson localization for multi-dimensional systems at large disorder or large energy

We prove that discrete Schrödinger operators on ^d with a random-potential have almost-surely only pure point spectrum and exponentially decaying eigenfunctions for large disorder or large energy. This is the first proof of localization for multi-dimensional Anderson models.Groupe de recherche 048 du CNRS     

Two new 5-deoxyflavones from Albizia odoratissima

Two new 5-deoxyflavones, 7,8-dimethoxy-3',4'-methylenedioxyflavone (1) and 7,2',4'-trimethoxyflavone (2) together with a known flavone, 7,4'-dimethoxy-3'-hydroxyflavone (3) were isolated from the rootbark of Albizia odoratissima. The structures of these new compounds were elucidated by electrospray ionization mass spectrometry (ESI-MS) and 1D and 2D-NMR spectral studies including (1)H-(1)H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY).     

Multicomponent coupling approach to (+/-)-frondosin B and a ring-expanded analogue

[reaction: see text] A recently discovered multicomponent coupling reaction is used to give direct access to a late intermediate in the synthesis of frondosin B. This intermediate can also be efficiently converted to a ring-expanded analogue of frondosin B by sustained heating of the reaction mixture. An unprecedented tandem 1,7-hydrogen shift, 8pi-electrocyclization is proposed to explain the formation of this ring-expanded species.     

Conformational behavior of nonfused biheterocycles: Part XVI. Isomeric phenyl-tetrazines and bitetrazines

We present here an ab-initio STO-3G and advanced semiempirical AM1 calculation for the structure and the conformational behavior of phenyltetrazine and bitetrazine molecules. Results for phenyltetrazine isomers show that in the absence of H-H interactions, the preferred conformation is the planar one. Instead, in the case of bitetrazines, the systems dominated by the lone pair-lone pair interactions are not planar. In the presence of direct H-H interaction as for 5-5-1,2,3,4 bitetrazine, the antiplanar conformation is the preferred one. Comparison with other systems (including one or more nitrogen lone pairs) shows that the compounds with the same ortho substituents have very similar conformational behavior irrespective of their composition. The AM1 results indicate that this method is able to give reliable conformational information for compounds in which H-H interactions are involved. A Fourier expansion of the torsional potential suggests that the first two terms fit the calculated torsional potentials well except in the case of two H-H interactions in the same molecule.     

1,3,5-Trisubstituted hexahy drotriazines as mannich reagents. I. Preparation of secondary aminomethyl sulfide hydrochlorides

1,3,5-Trisubstituted hexahy drotriazines react with hydrogen chloride in the presence of anhydrous solvents to form useful intermediates for the introduction of the RNHCH₂- group into compounds which undergo the Mannich reaction. The effectiveness of the new aminomethyl-ating agent has been demonstrated by the preparation of secondary aminomethyl sulfide hydro-chlorides.     

Identification by Electron Probe Microbeam Analysis of Submicron Borides in Joints of Nickel Base Superalloys

The phases formed at the interface between an intermetallic (NiAl) and a nickel base superalloy joined by combustion synthesis were investigated, particularly the eutectic phases. Owing to their small size, the characterisation of these phases using a Castaings electron microprobe encounters difficulties. The analysis volume size is generally too large to differentiate the phases from their surrounding matrix, even by using low accelerating voltage. Moreover, the eutectic phases contain boron, which is difficult to characterise by EPMA. Independently of the phases shape, the characterisation can be solved by viewing this complex system as a surrounding matrix and a multi layer system. The results of these simulations revealed the presence of two categories of borides: the eutectic boride MM₂B₂ (M=Mo and M=Co, Cr) and the solid solution boride [Cr_1–x (Mo, W)_x]B.     

Studies of pyrolysis and air heating of rayon by inverse gas chromatography

Inverse gas chromatography using water probing at 110°C was carried out to characterize rayon yarns after prior heating at 200 and 250°C in both inert (nitrogen) and oxidative (dry air) atmospheres for successively longer time intervals. During the early stages of heating in either atmosphere, the affinity of the rayon for water drops rapidly. However, whereas continued heating in N₂ results in a further loss of activity, data have been obtained showing that after an initial period yarns heated in air at 250°C exhibit an increasing attraction for water even while losing more weight.     

Behaviour of Pluronic P84 block copolymer micelles above the gelification temperature as probed by positron annihilation lifetime spectroscopy

The new method based on positron annihilation lifetime spectroscopy (PALS) to determine both the mean core radius, R(core), and aggregation number, N(ag), of micelles is applied to the study of aqueous solutions of the triblock Pluronic P84 copolymer as a function of temperature (T), beyond the gelification point (334 K). Two long-lived components appear in the PALS spectra, ascribed to triplet positronium in the water bulk (o-Ps(aq)) and in the organic core of the micelles (o-Ps(org)). Of the various fitting parameters, only the lifetime of the latter species, tau4, and the micellar parameters, R(core) and N(ag), disclose the occurrence of gelification by first increasing up to 334 K, then decreasing. By contrast to what is known in case of phase transition, none of the parameters shows any abrupt change at 334 K, whereas the macroscopic viscosity of the solutions suffers a drastic increase. This is attributed to the fact that positronium is sensitive to the microviscosity of the solutions. At the transition point, the properties of the polyoxipropylene aggregates forming the organic core of the P84 micelles are not greatly affected. Furthermore, the fact that the experimental N(ag) values coincide with those calculated for spheres, from the R(core) values, indicates that the shape of the P84 cores does not change significantly after gelification. The onset of gelification results from a decrease in the hydrogen bonding interactions in the solution with an ensuing relative increase in the interactions between the polyoxipropylene (PPO) groups, initially forming the corona of the P84 micelles, in an intermicellar mode. This increased solicitation of the PPO groups outside their initial location would result in depletion in the number of surfactant molecules forming the micelles, viz. a decrease in both R(core) and N(ag) above 334 K. From the data, additional information can be gained regarding the local viscosity and surface tension in the micellar cores.