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31.
New tetracyclic derivatives (3a,, 5, 8) similar to protoberberines, but containing a lactam structural element and other hetero atoms besides the bridge-head nitrogen in rings B and C, were prepared by cycloaddition of 6,7-dimethoxy-2H-1,3-benzothiazine (1a) with -substituted aromatic carboxylic acid derivatives (2a,, 4) and from 4- methyl-6,7-dimethoxy-2-1,3-benzothiazine (1b) with 3.5-dinitrobenzoyl chloride. 相似文献
32.
The effect of aliphatic alcohols on the reacting BZ system has been studied and the mechanism of alcohol inhibition interpreted.
.相似文献
33.
Expanding the Scope of Hypervalent Iodine Reagents for Perfluoroalkylation: From Trifluoromethyl to Functionalized Perfluoroethyl 下载免费PDF全文
Dr. Václav Matoušek Jiří Václavík Peter Hájek Julie Charpentier Zsófia E. Blastik Ewa Pietrasiak Alena Budinská Prof. Dr. Antonio Togni Dr. Petr Beier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(1):417-424
A series of new hypervalent iodine reagents based on the 1,3‐dihydro‐3,3‐dimethyl‐1,2‐benziodoxole and 1,2‐benziodoxol‐3‐(1H)‐one scaffolds, which contain a functionalized tetrafluoroethyl group, have been prepared, characterized, and used in synthetic applications. Their corresponding electrophilic fluoroalkylation reactions with various sulfur, oxygen, phosphorus, and carbon‐centered nucleophiles afford products that feature a tetrafluoroethylene unit, which connects two functional moieties. A related λ3‐iodane that contains a fluorophore was shown to react with a cysteine derivative under mild conditions to give a thiol‐tagged product that is stable in the presence of excess thiol. Therefore, these new reagents show a significant potential for applications in chemical biology as tools for fast, irreversible, and selective thiol bioconjugation. 相似文献
34.
General dual curvature measures have recently been introduced by Lutwak, Yang and Zhang [24]. These new measures unify several other geometric measures of the Brunn–Minkowski theory and the dual Brunn–Minkowski theory. dual curvature measures arise from qth dual intrinsic volumes by means of Alexandrov-type variational formulas. Lutwak, Yang and Zhang [24] formulated the dual Minkowski problem, which concerns the characterization of dual curvature measures. In this paper, we solve the existence part of the dual Minkowski problem for and , and we also discuss the regularity of the solution. 相似文献
35.
Zs. M. Jászay I. Petneházy L. Töke 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract During our attempts to prepare asymmetrically substituted carbodiimides of biochemical interest we have observed that phosphoramidate-esters react under phase-transfer conditions with isocyanates giving carbodiimides. 相似文献
36.
I. Petneházy Zs. M. Jászay Gy. Keglevich L. Toke 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract Reaction of trialkyl phosphites 1 with α,β-unsaturated oxo-compounds 2 gives oxaphospholenes 3 or/and two types of Arbuzov products, γ-keto-phosphonates 4 and alkyl-enol-ethers 5. 相似文献
37.
Abstract Polystyrene-polyisobutylene-polystyrene triblock copolymer thermoplastic elastomers have been synthesized by living carbocationic sequential copolymerization using the tert-butyl dicumyl chloride/TiCl4/methylcyclohexane:methyl chloride (60:40 v:v)/ ?80°C system in the presence of the proton trap 2,6-di-tert-butylpyridine. Structure-property relationships have been examined by varying the Mn of the PIB middle block (39,000 to 156,000) and that of the PSt end-segment (1,000 to 19,000). The tensile strength is controlled by the molecular weight of the PSt segment and independent of the PIB middle block length in the studied range. Phase separation starts when the Mn of the PSt segment reaches ~ 5,000, and it is complete when the Mn reaches ~ 15,000. These triblocks exhibited 23-25 MPa tensile strength, similar to that of styrenic thermoplastic elastomers obtained by anionic polymerization. 相似文献
38.
I. Lukovits J. Fodor Á. Gömöry K. István G. Keresztury L. Kótai 《SAR and QSAR in environmental research》2013,24(3):323-335
The presence and absence of alkane isomers in petroleum and petroleum derivatives depend on the complexity of these structures. It was assumed that the more complex the structure is the less probable it is that that the molecule can be detected in any petroleum derivative. Complexity is a vague concept, which has not been defined in quantitative terms yet, and therefore there is no experimental method, which could be used to determine ‘complexity’. Mass spectrometry and infrared spectroscopy in combination with gas chromatography were used to identify the various structural isomers of alkanes in petroleum ether. The isomers were categorised in quantitative terms by using topological indices and linear discriminant analysis. It was found that alkanes possessing a more complex, highly branched structure are less probable to be detected in petroleum ether than isomers with a simpler backbone structure. It was proposed that the experimental ‘measure’ of the complexity of isomeri should be proportional to 1/Ci , where Ci , denotes the concentration of isomeri in a (primary) petroleum derivative. 相似文献
39.
Michael E. Cates tienne Fodor Tomer Markovich Cesare Nardini Elsen Tjhung 《Entropy (Basel, Switzerland)》2022,24(2)
Many complex fluids can be described by continuum hydrodynamic field equations, to which noise must be added in order to capture thermal fluctuations. In almost all cases, the resulting coarse-grained stochastic partial differential equations carry a short-scale cutoff, which is also reflected in numerical discretisation schemes. We draw together our recent findings concerning the construction of such schemes and the interpretation of their continuum limits, focusing, for simplicity, on models with a purely diffusive scalar field, such as ‘Model B’ which describes phase separation in binary fluid mixtures. We address the requirement that the steady-state entropy production rate (EPR) must vanish for any stochastic hydrodynamic model in a thermal equilibrium. Only if this is achieved can the given discretisation scheme be relied upon to correctly calculate the nonvanishing EPR for ‘active field theories’ in which new terms are deliberately added to the fluctuating hydrodynamic equations that break detailed balance. To compute the correct probabilities of forward and time-reversed paths (whose ratio determines the EPR), we must make a careful treatment of so-called ‘spurious drift’ and other closely related terms that depend on the discretisation scheme. We show that such subtleties can arise not only in the temporal discretisation (as is well documented for stochastic ODEs with multiplicative noise) but also from spatial discretisation, even when noise is additive, as most active field theories assume. We then review how such noise can become multiplicative via off-diagonal couplings to additional fields that thermodynamically encode the underlying chemical processes responsible for activity. In this case, the spurious drift terms need careful accounting, not just to evaluate correctly the EPR but also to numerically implement the Langevin dynamics itself. 相似文献
40.
The electronpoor double-bond of cyclic vinylphosphine oxides (1, 3 and 4) is easily reduced by borane in a selective manner to give the corresponding saturated derivatives (2, 4 and 5, respectively) Under forcing conditions, change of the functionality may also take place. 相似文献