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51.
Charles B. de Koning Sunnyboy S. Manzini Joseph P. Michael Edwin M. Mmutlane Tefo R. Tshabidi Willem A.L. van Otterlo 《Tetrahedron》2005,61(3):555-564
The synthesis of substituted anthracenes from naphthalene precursors is described. The key step involved heating ortho-allyl substituted naphthalene-2-carbaldehydes and potassium t-butoxide in DMF with concomitant irradiation from a high pressure mercury lamp to afford anthracenes in yields of 76-98%. 相似文献
52.
Jacquelynn L. Savoca Robert P. Lattimer Joseph M. Richards Willem Windig Henk L.C. Meuzelaar 《Journal of Analytical and Applied Pyrolysis》1985,9(1):19-28
A set of twelve natural rubber vulcanizates was analyzed by Curie-point pyrolysis-mass spectrometry (Py-MS). Multivariate analysis successfully correlated the Py-MS data with either total or polysulfidic crosslink density measurements. (Polysulfidic means two or more sulfurs.) The principal correlation observed was an increase in the ratio of monomer to dimer pyrolyzate yield with an increase in crosslink density. The feasibility of using Py-MS for total crosslink density determination has thus been demonstrated. The Py-MS data, however, did not allow us to distinguish different types of crosslinks. 相似文献
53.
Joseph R. Lakowicz Ignacy Gryczynski Henryk Malak Zygmunt Gryczynski 《Photochemistry and photobiology》1996,64(4):632-635
Abstract— We report the observation of two-photon excitation of an organic fluorophore with two different wavelengths, a phenomenon we refer to as two-color two-photon (2C2P) excitation. Ultraviolet emission of p -Merphenyl at 340 nm was observed when the sample was illuminated with both 375 and 750 nm pulses from a picosecond dye laser. The emission of p -terphenyl was about 100-fold and more than 1000-fold less for illumination at only 375 or 750 nm, respectively. Observation of the 2C2P signal required temporal and spatial overlap of the 375 and 750 nm pulses. The amplitude of the signal depended on the polarization of each beam. 2C2P excitation can have applications in fluorescence microscopy and elsewhere when spatially localized excitation is desirable. 相似文献
54.
A procedure for synthesis of 2,4-diamino-6-substituted-5-deazapteridines (pyrido[2,3-d]pyrimidines) is described. Condensation of 1-piperidino-1-propene with ethoxymethylenemalononitrile afforded an enamino malononitrile adduct, which when treated with ammonia yielded 2-amino-3-cyano-5-methylpyridine. Cyclization to 2,4-diamino-6-methyl-5-deazapteridine could be effected with guanidine. Similar condensation of piperidinopropene with ethyl methoxymethylenecyanoacetate followed by cyclization with hydroxylamine gave 2-amino-3-carbethoxy-6-methylpyridine 1-oxide. Reduction with phosphorus trichloride afforded the pyridine base, however, attempts to cyclize the amino ester to 2-amino-4-hydroxy-6-methyl-5-deazapteridine were unusccessful. 相似文献
55.
Mary E. Carter James L. Nash Joseph W. Drueke James W. Schwietert George B. Butler 《Journal of polymer science. Part A, Polymer chemistry》1978,16(5):937-959
β-Nitrostyrene and many of its derivatives have been shown to yield high polymers via anionic initiation with alkoxide ions in protic solvents, e.g., alcohols. A study was conducted to determine the effect of certain substituents on the polymerization characteristics of representative monomers of this series and the properties of their polymers. A kinetic study was conducted and the relative rates of propagation were unexpectedly found to correlate well with brown's σ+ values. The rates of initiation of two representative monomers, β-nitrostyrene and p-methoxy-β-nitrostyrene, with sodium ethoxide were found to be 3.51 and 2.86 liter/mole sec, respectively. The rate of chain transfer in ethanol was studied qualitatively by using gel-permeation chromatography (GPC) to obtain molecular weight distribution (MWD) curves. The low values of the M w/M n ratios indicated little chain transfer in the protic solvent. 相似文献
56.
The chance to prepare sterically and inductively stabilized arsa‐ and phosphaalkenes of the type PhE=C(CF3)2 (E = As, P) by reacting phenyl‐bis(trimethylsilyl)‐arsane ( 1 ) and ‐phosphane ( 5 ), respectively, with hexafluoroacetone (HFA) was investigated. The insertion of the carbonyl function in one of the Si–E bonds was found to occur at temperatures between ?78 and 20 °C. The elimination of hexamethyldisiloxane, which in case of acylamides and ketones spontaneously follows the insertion and in case of RE(SiMe3)–CR′2(OSiMe3) at least can be initiated by solid sodium hydroxide as catalyst, turned out to be impossible for the primary products PhE(SiMe3)–C(CF3)2‐OSiMe3 [E = As ( 2 ), P ( 6 )]. 2 and 6 were characterized by analytical (C, H) and spectroscopic methods (IR, NMR, MS). 相似文献
57.
The ligand, 1,2-bis(difluorophosphino)ethane, (PF2C2H4PF2), reacts with Ni(CO)4 in the gas phase and in solution to produce carbon monoxide and a polymer, [Ni(PF2C2H4PF2)2]x. PF2C2H4PF2 displaces norbornadiene from (C7H8)Mo(CO)4 to yield the relatively air-stable complex, Mo(CO)4-(PF2C2H4PF2). Analysis of the infrared spectrum of the monomeric complex indicates that the ligand exhibits π-acceptor strength equal to PF2C6H10PF2. 相似文献
58.
A simple approach for deriving expressions for the limiting steady-state response of the open tubular electrode, under conditions of intermediate electrolytic yields, is described. This approach couples the principles of laminar fluid dynamics with the theory of the porous electrode reactor. The dependence of the limiting current, I1, on flow rate, Vf, has the form of I1 α Vmf , with m ? , depending upon the electrolytic yield. The effects of electroactive species depletion upon the detector response are discussed. Experimental results are incorporated to support the theoretical conclusions. For a tubular electrode (4-cm long) the degree of conversion decreases from 0.21 to 0.03 and m decreases from 0.42 to 0.32 as the flow rate increases from 0.15 to 3.5 ml min-1. 相似文献
59.
[reaction: see text] The enediamine tautomer of a variety of substituted amidine free bases reacts with nitric oxide (NO) to produce compounds containing a carbon-bound diazeniumdiolate [R1R2R3C-N(O)=NO-] functional group (previously called "nitrosohydroxylamines"). The new reaction has been shown to be quite general, although the nature of the products does vary. Amidines containing more than one replaceable hydrogen produce polydiazeniumdiolates as intermolecular salts, while those in which only one diazeniumdiolation can occur provide zwitterionic salts. These diazeniumdiolated amidines are shown to be useful NO donor compounds which undergo very slow spontaneous dissociation on dissolution in pH 7.4 phosphate buffer to produce mixtures of NO and nitrous oxide containing mostly NO. The most advantageous manifestation of the new discovery is the preparation of the monodiazeniumdiolated amidine zwitterions. Reaction of the medically relevant alpha-adrenergic agonists tetrahydrozoline and idazoxan produced monodiazeniumdiolated amidine zwitterions from which NO release was observed for up to 28 days and showed little sign of ending. The reaction should be applicable to a variety of pharmaceutical agents, including NO synthase inhibitors, antitumor agents, and antibacterials. 相似文献
60.
Briggs TF Winemiller MD Collum DB Parsons RL Davulcu AH Harris GD Fortunak JM Confalone PN 《Journal of the American Chemical Society》2004,126(17):5427-5435
The 1,2-addition of lithium phenylacetylide (PhCCLi) to quinazolinones was investigated using a combination of structural and rate studies. (6)Li, (13)C, and (19)F NMR spectroscopies show that deprotonation of quinazolinones and phenylacetylene in THF/pentane solutions with lithium hexamethyldisilazide affords a mixture of lithium quinazolinide/PhCCLi mixed dimer and mixed tetramer along with PhCCLi dimer. Although the mixed tetramer dominates at high mixed aggregate concentrations and low temperatures used for the structural studies, the mixed dimer is the dominant form at the low total mixed aggregate concentrations, high THF concentrations, and ambient temperatures used to investigate the 1,2-addition. Monitoring the reaction rates using (19)F NMR spectroscopy revealed a first-order dependence on mixed dimer, a zeroth-order dependence on THF, and a half-order dependence on the PhCCLi concentration. The rate law is consistent with the addition of a disolvated PhCCLi monomer to the mixed dimer. Investigation of the 1,2-addition of PhCCLi to an O-protected quinazolinone implicates reaction via trisolvated PhCCLi monomers. 相似文献