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31.
The efficient catalytic activation of donor–acceptor aminocyclopropanes lacking the commonly used diester acceptor is reported here in a (3 + 2) dearomative annulation with indoles. Bench-stable tosyl-protected aminocyclopropyl esters were converted into cycloadducts in 46–95% yields and up to 95 : 5 diastereomeric ratio using catalytic amounts of triethylsilyl triflimide. Tricyclic indoline frameworks containing four stereogenic centers including all-carbon quaternary centers were obtained.A catalytic dearomatization of indoles with D–A aminocyclopropane monoesters for the synthesis of highly substituted indolines. 相似文献
32.
Iain L. Marr Petra Kluge Laura Main Vincent Margerin Cyrille Lescop 《Mikrochimica acta》1995,119(3-4):219-232
Three sets of samples have been investigated in some detail. One set is from a river polluted by mine workings, containing substantial levels of Fe, Mn,Cu, Zn and Ni with traces of many other metals. The second set consists of typical estuarine sediments contaminated from a wide range of industrial sources, and the third set consists of oily drilling cuttings from the sea bottom in the vicinity of a North Sea oil production platform.These samples have been subjected to treatment 1) with EDTA at two different pH's (extracts) 2) with HNO3/H2O2 3) with HNO3/HCl and 4) with HNO3/HCl/HF (digests). EDTA recoveries, compared toaqua regia digests, are often very reproducible, not dependent on pH, and usually significantly low. Nitric/peroxide andaqua regia digests often give very close results suggesting that these are meaningful values indicating the maximum levels of polluting metals in the sediments. However, the triple acid digest with HF does sometimes give higher values (and reasonable agreement for CRM's such as MESS-1) but with poorer reproducibility. 相似文献
33.
Taylor P Lahti PM Carroll JB Rotello VM 《Chemical communications (Cambridge, England)》2005,(7):895-897
Stable radical 2-(6-uradinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (1) binds to hydrogen-bonding complement 2,6-di(propylamido)pyridine (DAP) in chloroform with Ka=220 M(-1) at 33 degrees C; ESI-MS shows not only 1:DAP complementary dyad formation, but also 1:(DAP)2 formation at higher concentrations of DAP. 相似文献
34.
Vaporisation et dissociation thermique des sulfures de phosphore P4S3, P4S7 et P4S10 a l'etat gazeux
J. Bouix R. Hillel H. Vincent Y. Monteil 《Journal of Thermal Analysis and Calorimetry》1977,12(3):371-382
Résumé Nous avons montré par spectrométrie Raman à chaud et mesure des tensions de vapeur que P4S3 se vaporise de façon congruente tandis que P4S7 et P4S10 se dissocient dès le début de leur vaporisation. P4S7 donne réversiblement P4S3 et soufre. P4S10 se dissocie irréversiblement en P4S7 et soufre. A l'état de vapeur non saturante, P4S3 se dissocie au-dessus de 600° avec formation de phosphore, de soufre et d'autres espèces non identifiées.Nous avons mesuré expérimentalement la capacité calorifique de P4S3 liquide, calculé celle de P4S3 gazeux et son entropie standard. Nous avons aussi estimé l'enthalpie standard de vaporisation de P4S3 à l'aide des mesures des tensions de vapeur saturante. Nous en avons déduit l'entropie standard de P4S3 liquide et son point d'ébullition.
Nous remercions Monsieur Letoffe du laboratoire du Professeur J. Bousquet, INSA de Lyon, 20 Avenue Albert Einstein 401, 69621 Villeurbanne, qui a r6alis6 pour nous les déterminations expérimentales des capacités calorifiques de P4S8 liquide. 相似文献
It is shown by Raman spectroscopy at high temperature and by vapor tensimetric measurements that the vaporisation of P4S3 is congruent, whereas P4S7 and P4S10 dissociate at the beginning of vaporisation. P4S7 gives P4S3 and sulfur reversibly. The dissociation of P4S10 into P4S7 and sulfur is irreversible. Above 600°, in non-saturated vapour the dissociation of P4S3 gives phosphorus, sulfur and some unidentified gaseous species. The heat capacity of liquid P4S3 has been measured. That of gaseous P4S3 and its standard entropy have been calculated. The vaporisation standard enthalpy of P4S3 has been estimated from the experimental results on the saturated vapour pressures. The standard entropy of liquid P4S3 and its boiling point have been derived from these data.
Zusammenfassung Mittels Raman-Spektrometrie bei erhöhter Temperatur und durch Messung der Dampfdrucke wurde festgestellt, daß sich P4S3 verflüchtigt, während P4S7 und P4S10 mit Beginn der Verflüchtigung dissoziieren. P4S7 ergibt reversibel P4S3 und Schwefel. Im Zustand ungesättigten Dampfes dissoziiert P4S3 oberhalb von 600° unter Bildung von Phosphor, Schwefel und anderer nicht identifizierter Substanzen.Die Wärmekapazität von flüssigem P4S3 wurde gemessen, während die vom gasförmigem P4S3 sowie seine Standard-Entropie berechnet wurden. Die Standard-Enthalpie der Verflüchtigung des P4S3 wurde durch Messungen der Sättigungs-Dampfdrucke ermittelt. Daraus wurden die Standard-Entropie des flüssigen P4S3 sowie sein Siedepunkt berechnet.
- - , P4S3 , P4S7 P4S10 . P4S7 P4S3 , P4S10 P4S7 . 600° P4S3 , . P4S3, P4S3 . P4S3. P4S3 .
Nous remercions Monsieur Letoffe du laboratoire du Professeur J. Bousquet, INSA de Lyon, 20 Avenue Albert Einstein 401, 69621 Villeurbanne, qui a r6alis6 pour nous les déterminations expérimentales des capacités calorifiques de P4S8 liquide. 相似文献
35.
Alain Merschaert Laurent DelhayeJean-Paul Kestemont Willy BrionePieter Delbeke Vincent MancusoFreddy Napora Khalid DikerDaniel Giraud Michel Vanmarsenille 《Tetrahedron letters》2003,44(24):4531-4534
A stereoselective approach has been developed for the synthesis of cis- and trans-2-methyl-4-arylpiperidines from a common intermediate. The Ni-catalyzed hydrogenolysis of N-Boc-2-methyl-4-aryl-4-piperidinols, obtained by addition of organometallic reagents on N-Boc-2-methyl-4-piperidone, afforded the trans derivatives with up to 95% selectivity whereas the corresponding cis isomers were obtained in the presence of palladium catalysts. 相似文献
36.
Jean BourguignonUlf Bremberg Georges DupasKristina Hallman Lars HagbergLaurent Hortala Vincent LevacherSerghey Lutsenko Emmanuel MacedoChristina Moberg Guy QuéguinerFredrik Rahm 《Tetrahedron》2003,59(48):9583-9589
Chiral pyridinooxazoline, quinolinooxazoline, bis(oxazolino)pyridine (pybox), and bisoxazoline (box) derivatives containing crown ether residues were prepared. Some of the ligands were assessed in substrate binding studies and in palladium catalyzed allylic alkylations. 相似文献
37.
Vincent Lapinte Laurent Fontaine Vronique Montembault Irne Campistron Danile Reyx 《Journal of molecular catalysis. A, Chemical》2002,190(1-2):117-129
ROMP and retro-acyclic diene metathesis (ADMET) were used for the synthesis of new functional polymers and functional oligomers, respectively. Purely exo and enantiomerically pure norbornene and 7-oxanorbornene derivatives were prepared using stereospecific synthesis, effective fractionation and high yield condensation reactions. Successful ROMPs of those monomers were performed using either the new carbenic Schrock’s or Grubb’s catalysts or in some cases a classical bicomponent catalyst. New functional polymers such as optically active poly(norbornene-2-carboxylic acid), reactive poly(norbornene-2-azlactone), and side-chain liquid crystal polyoxanorbornenes were fully characterized. On the other hand, successful depolymerizations of 1,4-polyisoprene and of epoxidized 1,4-polybutadiene via cross-metathesis with 4-octene were performed using a stabilized bicomponent catalyst and the Grubb’s catalyst, respectively. Conditions for the controlled synthesis of epoxidized oligobutadienes and of epoxydienic monomers via retro-ADMET were clearly defined. 相似文献
38.
J. S. Vincent A. H. Dougan D. L. Lyster J. W. Blue 《Journal of Radioanalytical and Nuclear Chemistry》1981,65(1-2):17-29
A facility for the continuous production of iodine-123 by spallation of elemental caesium by 482 MeV protons has been in operation
at a TRIUMF beam dump for about 2 years. Radioxenon from the target is efficiently trapped on alumina which is subsequently
used to remove the121Te decay product. The yield is 100 mCi/h from a 20 gm/cm2 target at 10 μA. Impurities are125I<2% and121Te<0.2% at 27 hours after end of production. The123I consists mainly of iodide along with significant iodate impurity. The product is used extensively in Canadian clinics for
thyroid analyses and for labelling radiopharmaceuticals. 相似文献
39.
Dugas V Broutin J Souteyrand E 《Langmuir : the ACS journal of surfaces and colloids》2005,21(20):9130-9136
DNA chips are potentially powerful technologies for genotyping and gene expression profiling that rely on comparative analyses of up to thousands of "spots of analysis" on a glass support. The spot quality throughout the support influences spot-to-spot variations within an array and the repeatability of data across experiments. For glass slide DNA microarrays, droplets of DNA solution are deposited on functionalized glass slides and left to react through complete evaporation of the droplet. On hydrophobic flat surfaces, different modes of droplet evaporation can be attained. Under atmospheric pressure, water droplets tend to evaporate under two main regimes. Initially, the droplet flattens with a constant contact area, and then the droplet shrinks at a constant contact angle. As a result, the diameter and morphology of thousands of spots on microarrays are not uniform. This leads to poor and unreliable data processing results. In this work, we report the evaporation of an aqueous solution under a constant contact area mode. Evaporation under reduced pressure and the effect of reagent additives to the solution have been investigated. Video microscopy and digital image analysis techniques were applied to monitor the evaporation of the droplets. A mixture of surfactants was developed to maintain a constant area regime during evaporation and to form homogeneous spots. The control of some physicochemical properties (wetting, evaporation rate) of the droplet allows the formation of well-controlled spots compatible with DNA grafting. The influence of surfactant molecules on the mechanisms of evaporation is also discussed. 相似文献
40.
The stereoselective synthesis of N-[(s) 1 - carbethoxybutyl)] (s) alanine and of (2S, 3aS, 7aS) 2-t.butoxycarbonyl perhydroindole are described. Their coupling produces the title compound 相似文献