An Efficient and Convenient Synthesis of 2-Thio[1,2,4]triazolo[1,5-c]quinazoline and its Derivatives

4-Hydrazinoquinazoline with carbon disulfide underwent a recyclization reaction. The title compound 2-thio[1,2,4]triazolo[1,5-c]quinazoline was obtained after treatment of 4-hydrazinoquinazoline with potassium ethylxanthogenate via a facile in situ Dimroth-like rearrangement of the expected [4,3-c] system. Its structure was established by X-ray diffraction study and confirmed by an independent synthesis, starting from o-aminobenzonitrile.     

Highly diastereoselective reduction of ferrocene bis-imines with methyllithium and the formation of C2-symmetric Zr complexes

Alkylation of ferrocene bis-imines Fc[N=C(H)Ar]2 (Ar = Ph, p-Tol) with MeLi was found to proceed in a highly diastereoselective fashion producing the C2-symmetric ferrocene diamines Fc[NC(H)(Me)Ar]2-H2 with 90% diastereomeric excess. This process allowed for the synthesis of C2-symmetric zirconium complexes Fc[NC(Me)Ar]ZrBn2.     

Electrophoretic separation of amyloid beta peptides in plasma

In this prospective study, for the first time we have separated and quantified amyloid beta (Abeta) peptides in the plasma of patients with Alzheimer's disease (AD, n = 8) and age- and environment-matched healthy controls (n = 9) with urea-based Abeta-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/immunoblot. In addition to the Abeta peptides 1-37/38/39/40/42, which we recently identified as regular constituents of human cerebrospinal fluid (CSF), we have observed a novel electrophoretic band migrating slightly cathodically to Abeta1-42. Since a standard peptide with the amino acid sequence Abeta2-40 migrates in the same position, we hypothesize that this plasma-specific band may correspond to Abeta2-40. The concentration of Abeta peptides in the plasma has been approximately 100-fold lower compared to the CSF. Interestingly, the concentration of the two shortest peptides and the longest one of these considered here (i.e., Abeta1-37/38/42) have increased significantly when the samples have been frozen at -80 degrees C before immunoprecipitation, while the 'middle-length' peptides (i.e., Abeta1-39/40) have not been affected by this procedure. We have not observed significant differences of the Abeta peptides concentrations between AD and control subjects. Our method can be used to investigate the significance of plasma Abeta peptides in neurodegenerative disorders, and to monitor the efficiency of drugs with beta/gamma-secretase inhibitory potency.     

A novel approach to fused 1,2,4-triazines by intramolecular cyclization of 1,2-diaza-1,3-butadienes bearing allyl(propargyl)sulfanyl and cyclic tert-amino groups

3-Allyl- and 3-prop-1-ynylsulfanyl-2-arylazo-3-cycloalkylamino-acrylonitriles undergo cyclization under mild conditions to afford the novel heterocyclic systems 1,4,6,7,8,8a-hexahydropyrrolo[2,1-c][1,2,4]-triazine-4-thione, 1,4,6,7,9,9a-hexahydro-[1,4]oxazino[3,4-c][1,2,4]triazine and 1,6,7,8,9,9a-hexahydro-4H-pyrido[2,1-c][1,2,4]triazine via a number of consecutive pericyclic reactions.     

Investigation of Inhomogeneites in Epitaxial AlxGa1−xN Layers Grown on Sapphire

 Procedures for the preparation of bevels and the determination of their geometrical parameters have been developed. Using these procedures study of compositional and optical spatially resolved inhomogeneities of Al_xGa_1−xN layers grown on (0001) sapphire have been studied by EPMA and cathodolu-minescence. It has been found that the nonuniform distribution in depth of Al in epitaxial layers grown under constant conditions is connected with presence of stresses in the layer.     

Substrate-induced pairing in 2,3,6,7,10,11-hexakis-undecalkoxy-triphenylene self-assembled monolayers on Au111

We present an STM study of self-assembled monolayers of 2,3,6,7,10,11-undecalkoxy-substituted triphenylene (T11) at the n-tetradecane/Au(111) interface under ambient conditions. T11 molecules self-organize as paired rows with molecules lying flat on the surface in an antiparallel position. Three alkyl chains of each T11 molecule align along the 110 direction of the underlying Au(111) substrate. The association of T11 in molecular pairs appears to result from a substrate-induced mechanism governed by the strong anisotropic interaction between T11 alkyl chains and Au(111).     

Twelve-membered crown ethers: Crystal structures of benzo-12-crown-4 and naphtho-12-crown-4

The crystal structures of two 12-membered crown ethers, benzo-12-crown-4 (1) and naphtho-12-crown-4 (2), have been determined by X-ray analysis. Both structures are molecular. Compound1 is monoclonic,P2₁/b,a=8.466(3),b=8.019(3),c=33.590(10) Å, =90.99(3)^o. The unit cell contains two crystallographically independent molecules of1 with similar conformations. Compound2 is also monoclinic,P2₁/a,a=24.148(8),b=14.535(4),c=7.987(5) Å, =102.87(2)^o. Two independent molecules in the unit cell have significantly different conformations. Supplementary data relating to this publication have been deposited with the British Library as Supplementary Publication No. SUP 82145 (19 pages).     

SCF and CASSCF studies of geometrical rearrangements in LiBO

The minimum energy path for the rearrangement LiOB OBLi was calculated with the SCF approximation using a double-zeta plus polarization basis set. Stationary points on the potential surface were studied with the help of the CASSCF method using different choices of active space. The results indicate that LiBO may be regarded as a polytopic type molecule. The relative energies of different geometrical configurations changed considerably when the CASSCF method was used, compared to those obtained at the SCF level, demonstrating the importance of correlation effects for this system.     

Synthesis and characterization of novel monocarbollide exo-closo-(pi-arene)biruthenacarboranes [(PPh3)mClRu(eta6-C6H5R)Ru'CB10H11-n(OMe)n] (where R = H, m = 2, n = 1; R = mu-PPh2, m = 1, n = 0, 1)

The monocarbon carborane [Cs][nido-7-CB(10)H(13)] reacts with the 16-electron [RuCl(2)(PPh(3))(3)] in a solution of benzene/methanol in the presence of N,N,N',N'-tetramethylnaphthalene-1,8-diamine as the base to give a series of 12-vertex monocarbon arene-biruthenacarborane complexes of two types: [closo-2-[7,11-exo-RuClPPh(3)(mu,eta(6)-C(6)H(5)PPh(2))]-7,11-(mu-H)(2)-2,1-RuCB(10)H(8)R] (5, R = H; 6, R = 6-MeO; 7, R = 3-MeO) and [closo-2-(eta(6)-C(6)H(6))-10,11,12-[exo-RuCl(PPh(3))(2)]-10,11,12-(mu-H)(3)-2,1-RuCB(10)H(7)R(1)] (8a, R(1) = 6-MeO; 8b, R(1) = 3-MeO, inseparable mixture of isomers) along with trace amounts of 10-vertex mononuclear hypercloso/isocloso-type complexes [2,2-(PPh(3))(2)-2-H-3,9-(MeO)(2)-2,1-RuCB(8)H(7)] (9) and [2,5-(Ph(3)P)-2-Cl-2-H-3,9-(MeO)(2)-2,1-RuCB(8)H(6)] (10). Binuclear ruthenacarborane clusters of both series were characterized by a combination of analytical and multinuclear NMR spectroscopic data and by single-crystal X-ray diffraction studies of three selected complexes, 6-8. In solution, isomers 8a,b have been shown to undergo the isomerization process through the scrambling of the exo-[RuCl(PPh(3))(2)] fragment about two adjacent triangular cage boron faces B(7)B(11)B(12) and B(8)B(9)B(12).     

A new synthetic method for the 2H-[1,2,3]thiadiazolo[5,4-b]indoles

The systematic study of oxidative cyclization of 3-hydrazono-1,3-dihydroindole-2-thiones has been carried out and a series of new 2H-[1,2,3]thiadiazolo[5,4-b]indoles has been prepared. The elaborated reaction represents an efficient method for the synthesis of fused 1,2,3-thiadiazoles.