ChemInform Abstract: Trends in Gas-Phase Fluoride Ion Affinities of Main-Group Oxyfluorides and Fluoride Sulfides. Generation and Characterization of the Fluoride Adducts of FAsO,FPO, FPO2, F2SiO,F4SO,FBO, F2SiS,FPS, FAsS,F2S2, and S2O by Ion Cyclotron Resonance Addition-Elimination Reactions.

Novel oxyfluoride and fluoride sulfide anions are generated by the isoelectronic replacement of F in a main-group polyfluoride by O- or S- via the reaction of either tBuO- or RS- (R: H, Me) with the polyfluorides.     

Formation, detection, and stability studies of neutral vanadium sulfide clusters

Neutral vanadium sulfide clusters are generated by the reaction of seeded hydrogen sulfide in a helium carrier gas with laser ablated vanadium metal within a supersonic nozzle. The exiting clusters are expanded into a vacuum in a molecular beam and are ionized by both ultraviolet (UV) and vacuum UV (VUV) laser radiation. The generated ions are detected by a time of flight mass spectrometer. With single photon ionization (SPI) employing VUV (118 nm) radiation, sulfur rich clusters (V(m)S(n), n>m+1) and hydrogen containing clusters (V(m)S(n)H(x), x>0) are observed. With multiphoton ionization (MPI) through nanosecond UV (193 nm) radiation, these sulfur rich and hydrogen containing clusters cannot be observed, indicating severe fragmentation generated by MPI and the importance of SPI in determining the neutral vanadium sulfide cluster distribution. With MPI through femtosecond UV (226 nm) radiation, a few sulfur rich and hydrogen containing clusters are detected, but most clusters observed by SPI are still undetected even by femtosecond MPI. Density functional theory calculations are applied to optimize energies and structures of the clusters with m=1-3 and n=0-7. The experimental results are well interpreted based on the calculations. The calculated and experimental results for vanadium sulfides are compared with those of vanadium oxides in literature.     

Mechanochemical reactions of elementary sulfur and iron sulfides with hydrogen,oxygen, and water

Mechanochemical reactions of elementary sulfur and iron sulfides with hydrogen, oxygen, and water were studied. Three reactions were discovered: (1) between elementary sulfur and dihydrogen, (2) between pyrite and dihydrogen, and (3) between elementary sulfur and water; these reactions are accompanied by hydrogen sulfide evolution. Mechanochemical synthesis of iron sulfide from the constituent elements in water involves hydrogen sulfide, which is generated by the reaction of elementary sulfur with water. We show that elementary sulfur is generated during pyrite oxidation by dioxygen during or after dispersion. In an oxygen-free medium, pyrite is more reactive to water than iron sulfide. Pyrite reacts with dihydrogen and water in an oxygen-free medium directly, avoiding the dissociation stage.     

Titanocene(II)-promoted, one-pot, three-component coupling of thioacetals, alkynyl sulfones, and carbonyl compounds: highly stereoselective formation of tert-homopropargyl alcohols

Titanocene alkylidene complexes, generated by desulfurizative titanation of thioacetals with Cp2Ti[P(OEt)3]2, reacted with alkynyl methyl sulfones to produce organotitanium species, which gave tert-homopropargyl alcohols with high diastereoselectivity on treatment with aromatic and alpha,beta-unsaturated ketones.     

Photogeneration and reactivity of 1,n-diphenyl-1,n-azabiradicals

The 1,5-diphenyl-1,5-azapentanediyl biradical Ia was generated by photolysis of 1,2-diphenylazacyclopentane (pyrrolidine 1a). Among the reaction pathways followed by Ia, C-N bond reformation with ring closure was found to be the predominating process, as determined by separate irradiation of either of the pure enantiomers of 1a. Disproportionation was a minor process and took place only via H abstraction by the C5 benzylic radical. Another minor pathway was C5-aryl coupling, with formation of 5-phenyl-2,3,4,5-tetrahydro-1H-benzo[b]azepine (4a), which is equivalent to photo-Claisen rearrangement of 1a. Likewise, the 1,4-diphenyl-1,4-azabutanediyl biradical Ib was generated by photolysis of 1,2-diphenylazacyclobutane (azetidine 1b). This species underwent predominating C2-C3 cleavage, as indicated by the extensive styrene formation. Although N1-C4 bond reformation also took place, this is not the major pathway occurring from Ib. Besides, C4-aryl coupling to give 4-phenyl-1,2,3,4-tetrahydroquinoline (4b) was also observed. All the possible reaction pathways were theoretically studied at the UB3LYP/6-31G computational level; the results were found to be in good agreement with the experimental observations.     

De novo ligand design to partially flexible active sites: application of the ReFlex algorithm to carboxypeptidase A, acetylcholinesterase, and the estrogen receptor

Reflex is a recent algorithm in the de novo ligand design software, SkelGen, that allows the flexibility of amino acid side chains in a protein to be taken into account during the drug-design process. In this paper the impact of flexibility on the solutions generated by the de novo design algorithm, when applied to carboxypeptidase A, acetylcholinesterase, and the estrogen receptor (ER), is investigated. The results for each of the targets indicate that when allowing side-chain movement in the active site, solutions are generated that were not accessible from the multiple static protein conformations available for these targets. Furthermore, an analysis of structures generated in a flexible versus a static ER active site suggests that these additional solutions are not merely noise but contain many interesting chemotypes.     

Formation of Highly Functionalized Thiophenes by Reaction of Tetramethylthiourea,Acetylenic Esters,and α‐Haloketones

The 1:1 zwitterionic intermediates generated by addition of tetramethylthiourea to dialkyl acetylenedicarboxylates are trapped by α‐haloketones to yield functionalized 2‐aminothiophenes in good yields.     

Boron-mediated stereoselective syntheses of gamma,gamma-disubstituted allenamides

Propargylic boranes generated by lithiation of optically active N-propargyloxazolidinones undergo reaction with a range of aldehydes to produce gamma,gamma-disubstituted allenamides with good diastereoselectivity.     

Automatic spectra interpretation,structure generation,and ranking

A new rule-based spectra interpretation system is described. It directly processes spectral files generated by spectrometers. Its internal information representation and the simultaneous use of several spectroscopic methods allow for the achievement of both high reliability and good performance. For small and medium sized molecules, the new program is capable of automatically reducing the solution space to under 3%.     

Photocatalytic Giese-Type Reaction with Alkylsilicates Bearing C,O-Bidentate Ligands

Herein, a photocatalytic Giese-type reaction with alkylsilicates bearing C,O-bidentate ligands as stable alkyl radical precursors has been reported. The alkylsilicates were prepared in one step from organometallic reagents. Not only primary, secondary, and tertiary alkyl radicals, but also elusive methyl radicals, could be generated by using the present reaction system. The generated radicals were trapped by electron-deficient olefins bearing various functional groups to give the desired alkyl adducts. The silicon byproduct can be recovered after the photoreaction. The radical generation process was investigated by theoretical calculations, which provided an insight into the facile generation of methyl radicals from methylsilicate bearing C,O-bidentate ligands.     

Dual-stage lithography from a light-driven, plasmon-assisted process: a hierarchical approach to subwavelength features

A hierarchy of lithographic-type imaging generating 3 μm lines incorporating subdiffraction limit features was obtained through a novel two-step reaction process. Photochemically generated ketyl radicals were used to make defined lines of silver nanoparticles. The excitation of nanoparticle surface plasmons was then used to generate highly localized heat that causes polymerization selectively on the surfaces of excited particles. The nylon-6 polymer that is generated serves as a solubility switch used to retain the features on the substrate selectively; various imaging techniques were used to establish the nature of the nylon shells. This work shows that the heat generated by plasmon excitation can be exploited to generate negative-type lithographic features with dimensions well below the diffraction limit.     

5-芳酰氨基-2-苯基-2H-1, 2, 4-噻二唑-3-酮的合成

用1-芳酰基-5-苯基-2-硫代双脲与溴进行氧化成环反应制备了九个新的5-芳酰氨基-2-苯基-2H-1, 2, 4-噻二唑-3-酮, 相应的1-芳酰基-5-苯基-2-硫代双脲可以通过苯基脲与酰基异硫氰酸酯加成制得。     

Copper‐Catalyzed One‐Pot Synthesis of N‐Sulfonylalkanimidoyl Thiocyanates from Sulfonyl Azides,Alkynes, and KSCN

Ketenimine intermediates generated by the addition of copper acetylides to sulfonyl azides are trapped by KSCN to afford N‐sulfonylalkanimidoyl thiocyanates in moderate‐to‐good yields.     

Preparation, properties, and reduction of heteroaromatic quinoids with 1,4-diazacyclopentadien-2-ylidene terminals

New n-type heteroaromatic quinoids with 1,4-diazacyclopentadien-2-ylidene terminals were prepared. These quinoids possess strong electron-accepting properties, comparable to dicyanomethylene analogues. Both the radical anions and dianions were generated by metal reduction using 3% Na-Hg in THF and were spectroscopically characterized.     

Metastable ion study of organosilicon compounds. Part XIV-trimethylsilylacetic acid, (CH(3))(3)SiCH(2)COOH, and its methyl ester, (CH(3))(3)SiCH(2)COOCH(3)

The unimolecular metastable decompositions of trimethylsilylacetic acid, (CH(3))(3)SiCH(2)COOH (1), and its methyl ester, (CH(3))(3)SiCH(2)COOCH(3) (2), were investigated by mass-analyzed ion kinetic energy (MIKE) spectrometry in conjunction with thermochemical data. The abundance of the molecular ions of both compounds, generated by electron ionization, is extremely low. However, the abundance of the ions generated by the loss of (.)CH(3) and observed at m/z 117 and 131 is moderate. These fragment ions further decompose to form the most abundant m/z 75 and 89 ions, respectively, by the loss of CH(2)CO through a (CH(3))(2)Si group migration. The loss of CH(2)CO is also observed to occur from 2(+.) and its fragment ion at m/z 115 generated by the loss of (.)OCH(3). The former reaction is proposed to occur via an ion-radical complex.     

One-pot synthesis of partially fluorinated naphthalene, anthracene, and chrysene derivatives

A series of partially fluorinated naphthalene, anthracene, and chrysene derivatives have been synthesized by a convenient one-pot reaction of multi-fluorinated aromatics and 1,4-dilithio-1,2,3,4-tetraaryl-1,3-butadiene that was generated in situ from the reduction of diphenylacetylene derivatives with lithium naphthalenide.     

Synthesis,Fluorescence and Electrochemistry of a New ECL-active Species

Recently, there has been much interest in electrochemiluminescence (ECL) generated from tris (2,2 -bipyridine) ruthenium (II) because of its application in iinmmunoassay, nucleic acid hybridization assay, and detection of other important chemical, biochemical, and biological substances. ECL is a technique by which a chemiluminescent reaction is generated from reagents produced in the vicinity of an electrode surface when a potential is applied.     

Synthesis of the new mannosidase inhibitors, diversity-oriented 5-substituted swainsonine analogues, via stereoselective Mannich reaction

5alpha-substituted swainsonine analogues were synthesized by Mannich reaction of an in situ generated (-)-swainsonine iminium ion intermediate. 5alpha-substituted swainsonine analogues were epimerized to their 5beta-isomers in protic solvent. [reaction: see text]     

Aggregation mechanism of polyglutamine diseases revealed using quantum chemical calculations, fragment molecular orbital calculations, molecular dynamics simulations, and binding free energy calculations

Polyglutamine (polyQ) diseases, including Huntington’s disease (HD), are caused by expansion of polyQ-encoding repeats within otherwise unrelated gene products. The aggregation mechanism of polyQ diseases, the inhibition mechanism of Congo red, and the alleviation mechanism of trehalose were proposed here based on quantum chemical calculations and molecular dynamics simulations. The calculations and simulations revealed the following. The effective molecular bonding is between glutamine (Gln) and Gln (Gln + Gln), between Gln and Congo red (Gln + Congo red), and between Gln and trehalose (Gln + trehalose). The bonding strength is −13.1 kcal/mol for Gln + Gln, −24.4 kcal/mol for Gln + Congo red, and −12.0 kcal/mol for Gln + trehalose. In the polyQ region, both the number of intermolecular Gln + Gln formations and the total calories generated by the Gln + Gln formation are proportional to the number of repetitions of Gln. We propose an aggregation mechanism whose heat generated by the intermolecular Gln + Gln formation causes the pathogeny of polyQ disease. In our aggregation mechanism, this generated heat collapses the host protein and promotes fibrillogenesis. Without contradiction, our mechanism can explain all the experimental results reported to date. Our mechanism can also explain the inhibition mechanism by Congo red as an inhibitor of polyglutamine-induced protein aggregation and the alleviation mechanism by trehalose as an alleviator of that aggregation. The inhibition mechanism by Congo red is explained by the strong interaction with Gln and by the characteristic structure of Congo red.