Volume and heat capacity of model non-aqueous self-assembly systems

Blends of immiscible polymers are often stabilized by block copolymers which can form non-aqueous micelles and microemulsions in the liquid polymers. The phase diagrans, apparent volumes and apparent heat capacities of model non-aqueous binary and ternary systems were studied in order to investigate the conditions under which such self-assembly systems could form. 1,2-Hexanediol, which can cosolubilize hexane and ethyleneglycol, forms inverse micelles in hexane and weak microaggregates in ethyleneglycol. Genapol X-060, a commercial alcoholic surfactant containing on the average an aliphatic chain of 13 carbons and 6 oxyethylenes (C₁₃E₆), forms microaggregates in poly(ethyleneglycol) 400. These self-assembly systems are strengthen in the presence of a third component which has an affinity for the inner phase.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

Electronic structure of dysprosium silicide films grown on a Si(1 1 1) surface

The thickness-dependent electronic structures of Dy silicide films grown on a Si(1 1 1) surface have been investigated by angle-resolved photoelectron spectroscopy. Two (1×1) periodic bands, both of them cross the Fermi level, have been observed in the silicide films formed by Dy coverages of 1.0 monolayer and below, and more than five () periodic bands have been observed in thicker films. Taking the () periodic structure of Dy atoms in the submonolayer silicide film into account, the periodicity of the two metallic bands indicate that they mainly originate from the orbitals of Si atoms, which form a (1×1) structure. Of the () periodic bands observed in thick films, four of them are well explained by the folding of the (1×1) bands into a () periodicity. Regarding the other band, the three () periodic bands would originate from the electronic states related to the inner Si layers that form a () structure, and the one observed in the 3.0 ML film only might originate from the electron located at the interface between bulk Si and the Dy silicide film.     

Different properties of exciplexes and excited states of CT complexes in the solid phase

The fluorescence, excitation and absorption spectra and fluorescence decay kinetics of charge-transfer (CT) complexes and exciplexes ofheteroaromatic cations and some other electron acceptors were investigated in ethanol at 77 K. Experimental data indicate that the fluorescence state of the exciplex may differ from that of the CT complex.     

The effect of the gas atmosphere on the phase transformation in the solid solution of MoO3 in V2O5

The nature of the structure transformation occurring under the influence of oxidizing or reducing gas atmosphere in powdered oxide (V₂O₅)_0.93 (MoO₃)_0.07 has been investigated. The formation of an intermediate compound in the inner parts of the catalyst grains during the oxidation and in the subsurface layers during the reduction has been observed.     

Stereoselective synthesis of dinucleoside phosphate aryl esters by using new condensing reagents,arenesulfonyl 5-(pyridin-2-yl)-tetrazole1

Deoxyadenylyl-(3'-5')-phosphoro-o-chlorophenyl deoxyadenosine having the Sp configuration was synthesised stereoselectively by condensing N,5'-bis-dimethoxytrityldeoxyadenosine 3'-(o-chlorophenyl) phosphate with N,3'-bis-dimethoxytrityldeoxyadenosine using 1-2,4,6-triisopropylbenzene-5-(pyridin-2-yl) tetrazole as the activating reagent followed by dedimethoxytritylation. The absolute configuration of this diastereomer was determined spectroscopically by comparison of two corresponding diastereomers which were prepared by using a conventional condensing reagent and isolated by chromatography on silica gel. Their nuclear Overhauser effect in proton magnetic resonances and the circular dichroism of these two diastereoisomers could only be explained if the product obtained by the stereoselective synthesis had Sp configuration. Our results also suggest that phosphotriesters of this type exist in solution as an equilibrium of folded and extended forms.     

Stereoselective preparation of methylenecyclobutane-fused angular tetracyclic spiroindolines via photosensitized intramolecular [2+2] cycloaddition with allene

Irradiation of 3-(hexa-4,5-dienyl)indole derivatives in the presence of 3′,4′-dimethoxyacetophenone by a high-pressure mercury lamp through Pyrex glass gave the corresponding [2+2] cycloaddition products stereoselectively in high yields. The major product was a methylenecyclobutane-fused angular tetracyclic spiroindoline derivative produced by the [2+2] cycloaddition through a parallel orientation. The minor product was a hexahydromethanocarbazole derivative through a crossed orientation. Electron-withdrawing substituents, such as acyl or alkoxycarbonyl, on the indole nitrogen were suitable for this reaction.     

Asymmetric Syntheses of Pharmaceutically Interesting Piperidines

Alkyl-3-hydroxyl piperidine is a structural unit found in numerous bioactive natural products, drugs and drug candidates. For example, (+)-L-733 060 (1)1 and (+)-CP-99, 994 (2)2 are selective and potent neurokinin substance P receptor antagonists, which have been shown to possess potent antiemetic activity; febrifugine (3)3 and isofebrifugine (4)3 are well-known candidates of antimalarial agents isolated from Chinese medicinal plants Dichroa febrifuga. The important bioactivities, common str…     

A new efficient synthetic methodology for tetrahydroisoquinoline and tetrahydro-β-carboline derivatives using the Pictet–Spengler reaction

A new solution-phase methodology microwave-assisted for improving the Pictet-Spengler reaction in the synthesis of the tetrahydroisoquinoline and beta-carboline derivatives has been reported. This methodology was applied to obtain a small library of tetrahydroisoquinoline and beta-carboline derivatives using L-Dopa, dopamine, and tryptophan, as well as a variety of commercially available aldehydes as starting material. The use of such nonconventional reaction conditions reveals several features like a short reaction time compared to conventional eating, ease of isolation of the products after work-up, and improvement of the yields. This new one-pot protocol would be an ideal and rapid method to synthesize compounds in a combinatorial context.