Infrared absorption spectra and structure of 1, 1, 4, 4-tetrasubstituted 1, 4-disilacyclohexanes

The IR absorption spectra of 1,1,4,4-tetramethyl- and 1,1,4,4-tetraphenyl-1,4-disilacyclohexanes have been studied. The group spectral analysis of these compounds shows that the silicon atoms have barene properties. The presence at about 980 cm^–1 of one strong band (and not two) of C-C stretching vibrations in agreement with the selection rules confirms the chair form of the heterocycle.     

Chemo- and diastereoselectivity in the dimethyldioxirane oxidation of 2,3-dihydro-4H-1-benzothiopyran-4-ones and 4H-1-benzothiopyran-4-ones. Unusual reactivity of 4H-1-benzothiopyran-4-one 1-oxides

The oxidation of the 1-thiochromanones 1-3 by dimethyldioxirane (DMD) produced the corresponding sulfoxides 4-6 or sulfones 7-9; their relative amounts depended on the amount of oxidant used. A low diastereoselectivity was observed in the sulfoxidation of the 2-substituted 1-thiochromanones 2 and 3, due to the small steric differentiation during the DMD attack. An unusual reactivity pattern was found in the DMD oxidation of the 1-thiochromones 10-12, in that the sulfoxides 13-15 were more reactive toward the electrophilic oxidizing agent than the corresponding sulfides. The observed anomaly may be explained in terms of transannular stabilization of the transition structure (TS) for the sulfone formation, promoted through favorable conformational effects in the sulfoxide. Higher sulfoxide/sulfone ratios were found in solvents of greater hydrogen bond donor capacity, which is in accordance with the postulated stabilizing effect.     

In situ X-ray absorption and diffraction studies of carbon coated LiFe1/4Mn1/4Co1/4Ni1/4PO4 cathode during first charge

Synchrotron based in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques are used to study electronic and crystal structure changes of the carbon coated LiFe_1/4Mn_1/4Co_1/4Ni_1/4PO₄ (LiFe_1/4Mn_1/4Co_1/4Ni_1/4PO₄/C) cathode material for Li-ion batteries during the first charge. In situ Fe, Mn, Co and Ni K-edge XAS results revealed that the three voltage plateaus at ～3.6, 4.2 and 4.7 V vs. Li/Li⁺ are attributed to the redox reactions of Fe²⁺/Fe³⁺, Mn²⁺/Mn³⁺ and Co²⁺/Co³⁺, respectively, while the apparent capacities above 4.9 V is not originated from the Ni²⁺/Ni³⁺ redox, but very likely from the electrolyte decomposition. Interesting phase transition behaviors of LiFe_1/4Mn_1/4Co_1/4Ni_1/4PO₄/C were observed with the formation of an intermediate phase and the solid solution regions. Combined in situ XAS and XRD techniques indicate fast electronic structural changes and slow bulk crystal structural changes.     

Synthesis of 5-substituted 1-aryl-1H-pyrazole-4-acetonitriles, 4-methyl-1-phenyl-1H-pyrazole-3-carbonitriles and pharmacologically active 1-aryl-1H-pyrazole-4-acetic acids

Lithium aluminum hydride reduction of 5-substituted or unsubstituted ethyl or methyl 1-aryl-1H-pyrazole-4-carboxylates gave, generally in excellent yields, 5-substituted or unsubstituted 1-aryl-1H-pyrazole-4-methanols which afforded the corresponding 1-aryl-4-(bromomethyl)-1H-pyrazoles with hydrobromic acid in acetic acid solution. These crude intermediates gave by reaction with potassium cyanide in dimethylsulfoxide solution 1-aryl-1H-pyrazole-4-acetonitriles only in the case of 5-unsubstituted compounds, otherwise mixtures of 5-substituted 1-aryl-1H-pyrazole-4-acetonitriles and 4-methyl-1-phenyl-1H-pyrazole-3-carbonitriles were generally obtained. Acetonitriles IIIa,b,i,l gave in excellent yields the corresponding 1-aryl-1H-pyrazole-4-acetic acids Va,b,i,l by alkaline hydrolysis. Compounds Vb,i,l showed in the writhing test appreciable analgesic properties, associated with low acute toxicity; moreover, compound VI exhibited a statistically significant antiinflammatory activity in the carrageenan-induced edema assay.     

Allylstannation: VII. Preparation of carboxylic acid 1-alkene-4-yl and 1-alkyne-4-yl esters by transalkoxylation of 4-n-dibutylchlorostannoxy-1-alkenes and 4-n-dibutylchlorostannoxy-1-alkynes with acyl chlorides

Carboxylic acid 1-alkene-4-yl and 1-alkyne-4-yl, esters (RCH(CH₂CHCH₂)OCOR′ ad RCH(CH₂CCH)OCOR′, R = R′ or R ≠ R′ = alkyl or alkenyl group) can be readily prepared in high yields by transalkoxylation reactions between 4-n-dibutylchlorostannoxy-1-alkenes or 4-n-dibutylchlorostannoxy-1-alkynes with acyl chlorides. This represents a general route for preparation of esters containing allyl or propargyl groups.     

Synthesis of tetrahydroseleno-1 and telluro-1 pyranones-4

The synthesis of the unsubstituted tetrahydroseleno-1-pyranone-4 and its telluro analog is described as well as some of their physical properties.     

某些含芳碲基或烷碲基的1, 4-苯醌和1, 4-萘醌衍生物

四氯-1,4-苯醌(1)和2,3-二氯-1,4-萘醌(2)中的氯相当活泼,能和许多亲核试剂反应,如醇和酚;硫醇和硫酚;胺及许多含NH的杂环化合物。1和2与磷亲核试剂的反应也是已知的,本文报道1及2和芳碲基或烷碲基亲试剂的反应。     

New 4-pentafluorosulfanyl and 4-perfluoroalkylthio derivatives of 1-chloro-2-nitro- and 1-chloro-2,6-dinitrobenzenes

New 4-pentafluorosulfanyl and 4-perfluoroalkylthio derivatives of 1-chloro-2-nitrobenzene and 1-chloro-2,6-dinitrobenzene were prepared from the corresponding bis(4-chloro-3-nitrophenyl)disulfide and bis(4-chloro-3,5-dinitrophenyl)disulfide, respectively. The SF₅ derivatives were obtained by fluorination of the disulfides with AgF₂ according to Sheppard’s method, while perfluoroalkylation was carried out by means of thermolytic reactions with xenon(II) bis(perfluoroalkylcarboxylates). The introduction of fluorine-containing, electron-withdrawing substituents into the aromatic ring (in the presence of other deactivating groups) reinforces the activation of the halogen substituent towards nucleophilic attack. Several nucleophilic substitution reactions have been carried out with these compounds, and as a result, some N- and S-containing groups were introduced in the benzene ring. For example, the previously unknown SF₅, CF₃S, and C₂F₅S analogues of trifluralin (Treflan^®) were prepared and characterized. Additional synthetic possibilities for heterocyclic chemistry are presented on the basis of reactions of the new 1-chloro-2,6-dinitrobenzene derivatives with ethyl thioglycolate wherein fluorine-containing derivatives of benzothiazole N-oxide were obtained as the main products.     

Synthesis of 4-Bromo-1,1′:4′,1″-terphenyl and 4-Methyl-1,1′:4′,1″-terphenyl

Russian Journal of Organic Chemistry - Possible synthetic routes to 4-bromo-1,1′:4′,1″-terphenyl and 4-methyl-1,1′:4′,1″-terphenyl have been studied. Stevens...     

Expression of 4-1BB and 4-1BBL in thymocytes during thymus regeneration

4-1BB, a member of the tumor necrosis factor receptor (TNFR) superfamily, is a major costimulatory receptor that is rapidly expressed on the surface of CD4⁺ and CD8⁺ T cells after antigen- or mitogen-induced activation. The interaction of 4-1BB with 4-1BBL regulates immunity and promotes the survival and expansion of activated T cells. In this study, the expression of 4-1BB and 4-1BBL was examined during regeneration of the murine thymus following acute cyclophosphamide-induced involution. Four-color flow cytometry showed that 4-1BB and 4-1BBL were present in the normal thymus and were preferentially expressed in the regenerating thymus, mainly in CD4⁺CD8⁺ double-positive (DP) thymocytes. Furthermore, the CD4^loCD8^lo, CD4⁺CD8^lo and CD4^loCD8⁺ thymocyte subsets, representing stages of thymocyte differentiation intermediate between DP and single-positive (SP) thymocytes, also expressed 4-1BB and 4-1BBL during thymus regeneration but to a lesser degree. Interestingly, the 4-1BB and 4-1BBL positive cells among the CD4⁺CD8⁺ DP thymocytes present during thymus regeneration were TCR^hi and CD69⁺ unlike the corresponding controls. Moreover, the 4-1BB and 4-1BBL positive cells among the intermediate subsets present during thymus regeneration also exhibited TCR^hi/int and CD69^+/int phenotypes, indicating that 4-1BB and 4-1BBL are predominantly expressed by the positively selected population of the CD4⁺CD8⁺ DP and the intermediate thymocytes during thymus regeneration. RT-PCR and Western blot analyses confirmed the presence and elevated levels of 4-1BB and 4-1BBL mRNA and protein in thymocytes during thymus regeneration. We also found that the interaction of 4-1BB with 4-1BBL promoted thymocyte adhesion to thymic epithelial cells. Our results suggest that 4-1BB and 4-1BBL participate in T lymphopoiesis associated with positive selection during recovery from acute thymic involution.     

Synthese von 1, 2-annelierten 1, 4-Benzodiazepinen und 4, 1-Benzoxazepinen

The syntheses of 1, 2-annelated 1, 4-benzodiazepines (IV, Y = N) and 4, 1-benzoxazepines (IV, Y = 0) are described (Scheme 1). The key step is a nucleophilic aromatic substitution of 2-substituted piperazines (II, Z = N? CH₃), piperidines (II, Z = CH₂) or pyrrolidines (II, Z= (CH₂)₀) with activated aryl halides (I).