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21.
Pablo M. Fidelibus Gustavo F. Silbestri María T. Lockhart Sandra D. Mandolesi Alicia B. Chopa Julio C. Podestá 《应用有机金属化学》2007,21(8):682-687
In this paper we describe a three‐step synthesis of aryldi‐ and triboronic acids starting from phenols. Several substituted phenols (I) were converted into the corresponding aryldiethylphosphates (II) in good to excellent yields. The latter, on reaction with sodium trimethylstannide in liquid ammonia, under irradiation, afforded the aryl‐ and heteroarylpoly(trimethylstannyl) derivatives in 65–90% yield. The third step is the reaction of the organotin compounds with borane in THF, which leads to the corresponding arylpolyboronic acids in around 80% yield. In order to confirm their structure, some of the diboronic acids were converted into the corresponding pinacol esters. The results obtained in a study on the synthesis of various terphenyls through double and triple Suzuki couplings catalyzed by palladium acetate between the obtained arylpolyboronic acids and various aryl halides are also reported. These reactions proceeded with an average 65% yield, and also enabled us to confirm the structures of some of the diboronic acids. The structure of the new compounds was determined by 1H, 13C and 119Sn NMR spectroscopy, mass spectrometry and IR spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
22.
Deng H Cobb SL Gee AD Lockhart A Martarello L McGlinchey RP O'Hagan D Onega M 《Chemical communications (Cambridge, England)》2006,(6):652-654
The fluorinase enzyme from S. cattleya is applied as a catalyst for the efficient incorporation of [18F]-fluoride into [18F]-5'-fluoro-5'-deoxyadenosine, [18F]-5'-fluoro-5'-deoxyinosine and [18F]-5-fluoro-5-deoxyribose for positron emission tomography (PET) applications. 相似文献
23.
24.
Peter Borwein Richard Lockhart 《Proceedings of the American Mathematical Society》2001,129(5):1463-1472
The results of this paper concern the expected norm of random polynomials on the boundary of the unit disc (equivalently of random trigonometric polynomials on the interval ). Specifically, for a random polynomial
let
Assume the random variables , are independent and identically distributed, have mean 0, variance equal to 1 and, if 2$">, a finite moment . Then
and
as .
In particular if the polynomials in question have coefficients in the set (a much studied class of polynomials), then we can compute the expected norms of the polynomials and their derivatives
and
This complements results of Fielding in the case, Newman and Byrnes in the case, and Littlewood et al. in the case.
25.
We study the behaviour of the glued trees algorithm described by Childs et al. in [1] under decoherence. We consider a discrete time reformulation of the continuous time quantum walk protocol and apply a phase damping channel to the coin state, investigating the effect of such a mechanism on the probability of the walker appearing on the target vertex of the graph. We pay particular attention to any potential advantage coming from the use of weak decoherence for the spreading of the walk across the glued trees graph. 相似文献
26.
CoFe2O4-BaTiO3 composites were prepared using conventional ceramic double sintering process with various compositions. Presence of two phases
in the composites was confirmed using X-ray diffraction. The dc resistivity and thermoemf as a function of temperature in
the temperature range 300 K to 600 K were measured. Variation of dielectric constant (ɛ′) with frequency in the range 100 Hz to 1 MHz and also with temperature at a fixed frequency of 1 kHz was studied. The ac
conductivity was derived from dielectric constant (ɛ′) and loss tangent (tan δ). The nature of conduction is discussed on the basis of small polaron hopping model. The static value of magnetoelectric
conversion factor has been studied as a function of magnetic field. 相似文献
27.
28.
A Gurtu P K Malhotra I S Mittra P M Sood SC Gupta VK Gupta GL Kaul LK Mangotra Y Prakash NK Rao ML Sharma 《Pramana》1974,3(5):311-322
This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR em = 〈n s〉/〈n ch〉, where 〈n ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R em = 1·71 implies an effectiveA-dependence ofR A =A 0.18,i.e., a very weak dependence. Predictions ofR em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production. 相似文献
29.
Lo Fiego MJ Silbestri GF Chopa AB Lockhart MT 《The Journal of organic chemistry》2011,76(6):1707-1714
Bulky arylstannanes and bulky aroyl chlorides are good reaction partners for the synthesis of two-, three-, and even four-ortho-substituted benzophenones, in good to excellent isolated yields (47-91%). Three simple and direct routes, with differential advantages, are proposed: (i) a catalyst-free protocol, in o-dichlorobenzene (ODCB) at 180 °C; (ii) a room temperature protocol, using AlCl(3) (0.5 equiv), in dichloromethane (DCM); and (iii) a solvent-free, indium-promoted procedure. A radical mechanism is proposed for the indium-mediated reactions. 相似文献
30.
Iodide in the range 0.7–9.2 mg can be determined rapidly in the presence of other halides by means of its peroxidase-catalysed oxidation with hydrogen peroxide; the relative standard deviations are 0.3–2%. 相似文献