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1.
The o-, m-, and p-phenylene bis(1,3-dioxolanium) dications (4-6) and 2,4,6-triphenylene tris(1,3-dioxolanium) trication (7) have been prepared by the ionization of the corresponding 2-methoxyethyl benzoates in FSO(3)H or CF(3)SO(3)H at 40 and 60 degrees C, respectively. The charge delocalization in these carbocations was probed by (13)C NMR chemical shifts and substantiated by GIAO/DFT calculations. Relatively less charge is delocalized into the aromatic ring of the carbotrication 7. The rotational barrier around the C(+)-Ar bond for carbodications 4 and 5 was also estimated to be 8-10 kcal/mol. 相似文献
2.
1,1-Difluoroethysilanes (R3SiCF2CH3, R = Me or Et) were synthesized from 1,1-difluoroethyl phenyl sulfone and chlorosilanes using magnesium metal via reductive 1,1-difluoroethylation. It was confirmed that 1,1-difluoroethylsilanes were effective 1,1-difluoroethylating reagents for carbonyl compounds. 相似文献
3.
Synthesis of both symmetric and unsymmetric diaryl/aryl alkyl sulfones is easily achieved by Friedel-Crafts type sulfonylation of aromatics with suitable arene- or alkane-sulfonic acids in the presence of Nafion-H, a perfluorinated resinsulfonic acid catalyst. 相似文献
4.
Protonation of acylferrocenes (FeCOR) in FSO3H-SO2CIF(SO2) solution was studied by PMR spectroscopy. The site of protonation is found to be at the carbonyl oxygen atom. Temperature dependent PMR spectra of protonated acylferrocenes FeCROH+ (R = CH3, C2H5, C6H5, OCH3) were observed indicating intermolecular hydrogen exchange with the acid solvent system. In addition the PMR spectra of acylferrocenes in FSO3 H-SO2 CIF(SO2) were found to be dependent upon the acid concentration. 相似文献
5.
6.
Shi G Wu JT Li Y Geleziunas R Gallagher K Emm T Olah T Unger S 《Rapid communications in mass spectrometry : RCM》2002,16(11):1092-1099
7.
Deng Y Wu JT Lloyd TL Chi CL Olah TV Unger SE 《Rapid communications in mass spectrometry : RCM》2002,16(11):1116-1123
In this work, a high-throughput and high-performance bioanalytical system is described that is capable of extracting and analyzing 1152 plasma samples within 10 hours. A Zymark track robot system interfaced with a Tecan Genesis liquid handler was used for simultaneous solid-phase extraction of four 96-well plates in a fully automated fashion. The extracted plasma samples were injected onto four parallel monolithic columns for separation via a four-injector autosampler. The use of monolithic columns allowed for fast and well-resolved separations at a considerably higher flow rate without generating significant column backpressure. This resulted in a total chromatographic run cycle time of 2 min on each 4.6 x 100 mm column using gradient elution. The effluent from the four columns was directed to a triple quadrupole mass spectrometer equipped with an indexed four-probe electrospray ionization source (Micromass MUX interface). Hence, sample extraction, separation, and detection were all performed in a four-channel parallel format that resulted in an overall throughput of about 30 s per sample from plasma. The performance of this system was evaluated by extracting and by analyzing twelve 96-well plates (1152) of human plasma samples spiked with oxazepam at different concentrations. The relative standard deviation (RSD) of analyte sensitivity (slope of calibration curve) across the four channels and across the 12 plates was 5.2 and 6.8%, respectively. An average extraction recovery of 77.6% with a RSD of 7.7% and an average matrix effect of 0.95 with a RSD of 5.2% were achieved using these generic extraction and separation conditions. The good separation efficiency provided by this system allowed for rapid method development of an assay quantifying the drug candidate and its close structural analog metabolite. The method was cross-validated with a conventional liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay. 相似文献
8.
G.K. Surya Prakash Jinbo Hu Ying Wang George A. Olah 《Journal of fluorine chemistry》2005,126(4):527-532
A fluoride-induced nucleophilic (phenylthio)difluoromethylation method using TMS-CF2SPh has been achieved. This new methodology efficiently transfers “PhSCF2” group into both enolizable and non-enolizable aldehydes and ketones to give corresponding (phenylthio)difluoromethylated alcohols in good to excellent yields. Diphenyldisulfide can also be (phenylthio)difluoromethylated into PhSCF2SPh in high yield. The reaction with methyl benzoate, however, gives only low yield of (phenylthio)difluoromethyl phenyl ketone. The above-obtained PhSCF2-containing alcohols can be further transformed into difluoromethyl alcohols using an oxidation-desulfonylation procedure. This new type of nucleophilic (phenylthio)difluoromethylation methodology may have other potential applications in the medicinal and agrochemical fields. 相似文献
9.
G. A. Olah G. K. Surya Prakash P. Donald Katherine B. Loker Koop Lammertsma 《Research on Chemical Intermediates》1989,12(2):141-159
In this short review we have shown the importance of protosolvation of onium ions (containing non-bonded pairs of electrons)
in superacid catalyzed reactions. Such activation can result in unusual reactions such as aromatic alkylation with Meerwein’s
salts, aliphatic nitration with nitronium ion, alkylation of saturated hydrocarbons, greatly enhanced activity of acyl cations,
etc. Possibly such phenomena may be operative in hydroxylation reactions using protonated hydrogen peroxide in strong acid
solutions. Even the reactivity of halonium ions could be enhanced by protosolvation. Consequently, electrophilic protosolvation
may play a significant role in strogg acid catalyzed reactions. 相似文献
10.
Summary The effect of composition and flow rate of the mobile phase on the HPLC separation of hydrogenated buckminsterfullerene (C60Hn n=2–38) was investigated on BuckySep column. Toluene was used as the basic solvent and hexane, heptane, cyclohexane, THF,
acetonitrile, acetone, ethanol and 2-propanol as co-solvents. The fraction of co-solvents was varied 10–80%, and the flow
rate 1–0.1 mL min−1. Toluene-acetonitrile 65∶35 and toluene-acetone 50∶50 provided the best separation. Under the best conditions complete separation
of C60H2 and almost complete separation of the four most abundant isomers of C60H4 were achieved. Separation of derivatives with higher hydrogen content was very poor.
Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997 相似文献