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51.
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Benjamin D. Stevens Etzer DaroutVincent Mascitti Kim F. McClure 《Tetrahedron letters》2011,52(16):1949-1951
The synthesis of two unprecedented regioisomeric oxospiropyrazole piperidine scaffolds is detailed. Their potential utility as templates for drug discovery is also exemplified. Chemical stability and solid state conformation were also evaluated. 相似文献
53.
Jian-Cheng Li Michael Munchhof Joseph S. Warmus Paul D. Bonin Kim F. McClure 《Tetrahedron letters》2012,53(7):852-853
A straightforward synthesis of a 2,6-disubstituted-7,8-dihydro-6H-pyrano[2,3-6]pyrazine is described. The synthesis relies on a versatile dichloropyrazine–aldehyde intermediate and an olefination partner. 相似文献
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Anthony M. C. Davies Heather V. Britcher Jeremy G. Franklin Susan M. Ring Alex Grant William F. McClure 《Mikrochimica acta》1988,94(1-6):61-64
A new technique for utilising near-infrared spectroscopic data for quantitative analysis is proposed. The method uses a database of spectra stored in the form of the Fourier transform together with the associated chemical analysis. The spectrum of an unknown sample is compared to each member of the database and a small subset of very similar samples is isolated. The analyte value for the unknown is calculated from the analytical values of the subset. Results are given for the application of the method to the analysis of nicotine in tobacco. 相似文献
56.
D.W. Slocum Angela Carroll Sally Eilerman Ben McClure R.W. Holman 《Tetrahedron letters》2006,47(6):865-868
The relative basicities of solutions of n-BuLi in cyclohexane as a function of the addition of increasing increments of THF or TMEDA (designer media) have been assessed. As the chloro DMG is incapable of complexing to n-BuLi, it can neither affect the n-BuLi oligomeric equilibrium nor exhibit a DoM mechanistic component involving prior-coordination (CIPE). Accordingly, by measuring the rates of loss of chlorobenzene in the varied media as well as by certain 7Li NMR studies, a gradual, controlled increase in the basicity of n-BuLi in cyclohexane with increasing increments of THF or TMEDA was observed. Relationships of the basicity in the varied media to the three oligomeric forms of n-BuLi are proposed. 相似文献
57.
(π-Cyclopentenyl)(π-cyclopentadienyl)nickel, (h5-C5H5)Ni(h3-C5H7), is a novel, highly active, unicomponent catalyst for the conversion of ethylene to n-butenes and n-hexenes at 145–150° C. At high conversions of ethylene (70–90%), the dimeric product (80–86% yield) contains a high percentage (90–82%) of 1-butene. Experimental evidence is presented which strongly indicates that the cyclopentadienyl group remains bonded to the nickel during catalysis while the cyclopentenyl group is labile. A possible mode of activation is the reversible elimination of cyclopentadiene from (h5-C5H5)N1(h3-C5H7) to generate π-cyclo pentadienylnickel hydride as a catalytically active intermediate. An improved synthesis of the title compound (70% yield) by direct hydrogenation of nickelocene is also reported. 相似文献
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Germain ME Vargo TR McClure BA Rack JJ Van Patten PG Odoi M Knapp MJ 《Inorganic chemistry》2008,47(14):6203-6211
Nitroaromatics and nitroalkanes quench the fluorescence of Zn(Salophen) (H2Salophen = N,N'-phenylene-bis-(3,5-di- tert-butylsalicylideneimine); ZnL(R)) complexes. A structurally related family of ZnL(R) complexes (R = OMe, di-tBu, tBu, Cl, NO2) were prepared, and the mechanisms of fluorescence quenching by nitroaromatics were studied by a combined kinetics and spectroscopic approach. The fluorescent quantum yields for ZnL(R) were generally high (Phi approximately 0.3) with sub-nanosecond fluorescence lifetimes. The fluorescence of ZnL(R) was quenched by nitroaromatic compounds by a mixture of static and dynamic pathways, reflecting the ZnL(R) ligand bulk and reduction potential. Steady-state Stern-Volmer plots were curved for ZnL(R) with less-bulky substituents (R = OMe, NO2), suggesting that both static and dynamic pathways were important for quenching. Transient Stern-Volmer data indicated that the dynamic pathway dominated quenching for ZnL(R) with bulky substituents (R = tBu, DtBu). The quenching rate constants with varied nitroaromatics (ArNO2) followed the driving force dependence predicted for bimolecular electron transfer: ZnL* + ArNO2 --> ZnL(+) + ArNO2(-). A treatment of the diffusion-corrected quenching rates with Marcus theory yielded a modest reorganization energy (lambda = 25 kcal/mol), and a small self-exchange reorganization energy for ZnL*/ZnL(+) (ca. 20 kcal/mol) was estimated from the Marcus cross-relation, suggesting that metal phenoxyls may be robust biological redox cofactors. Electronic structure calculations indicated very small changes in bond distances for the ZnL --> ZnL(+) oxidation, suggesting that solvation was the dominant contributor to the observed reorganization energy. These mechanistic insights provide information that will be helpful to further develop ZnL(R) as sensors, as well as for potential photoinduced charge transfer chemistry. 相似文献
60.