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71.
Wai Kean Goh 《Tetrahedron letters》2007,48(51):9008-9011
A versatile method for the synthesis of new 7-substituted 5,6-dihydroindol-2-ones is described. The synthetic strategy proceeds through the use of the established palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of halogenated indol-2-ones and arylboronic acids/esters. 相似文献
72.
Blends of poly(acrylic acid) (PAA) and poly(p‐vinylphenol) (PVPh) were prepared from N,N‐dimethylformamide (DMF) and ethanol solutions. The DMF‐cast blends exhibited single Tg's, as shown by modulated differential scanning calorimetry, whereas the ethanol‐cast blends had double Tg's. Fourier transform infrared spectroscopy showed that there was a specific interaction between PAA and PVPh in the DMF‐cast blends. The single‐Tg blends cast from DMF showed single‐exponential decay behavior for the proton spin–lattice relaxation in both the laboratory frame and the rotating frame, indicating that the two polymers mixed intimately on a scale of 2–3 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 789–796, 2003 相似文献
73.
We introduce a simple algorithm that constructs scale-free random graphs efficiently: each vertexi has a prescribed weight Pi ∝ i-μ (0 < μ< 1) and an edge can connect verticesi andj with rateP
i
P
j
. Corresponding equilibrium ensemble is identified and the problem is solved by theq → 1 limit of the q-state Potts model with inhomogeneous interactions for all pairs of spins. The number of loops as well
as the giant cluster size and the mean cluster size are obtained in the thermodynamic limit as a function of the edge density.
Various critical exponents associated with the percolation transition are also obtained together with finite-size scaling
forms. The process of forming the giant cluster is qualitatively different between the cases of λ > 3 and 2 < λ < 3, whereλ
= 1 +μ
-1
is the degree distribution exponent. While for the former, the giant cluster forms abruptly at the percolation transition,
for the latter, however, the formation of the giant cluster is gradual and the mean cluster size for finiteN shows double peaks. 相似文献
74.
A highly efficient iodine-catalyzed allylation of 1,3-dicarbonyl compounds with a wide variety of allylic alcohols has been developed. The reaction is operationally straightforward and proceeds under very mild conditions at room temperature in good to excellent yields (up to 99%) and regioselectivity. 相似文献
75.
As a brief sequel to our previous stability analysis of dumbbell molecule in torsional flow [1] we demonstrate that the motion of a dumbbell molecule in a continuous squeezing flow is also unstable at sufficiently large. Weissenberg number. The cause of instability in the present case, however, is quite different from the previous case. The mechanism responsible for triggering the instability is mainly attributed to the additional elongational flow component over the basic shear flow. The present flow situation is also different from the previous case in that the system is stochasticaly non-stationary, hence no steady-state average quantities can be obtained statistically. 相似文献
76.
Poly(neopentyl glycol adipate), PDPA, was found to be miscible with poly(epichlorohydrin-co-ethylene oxide). PDPA also formed miscible blends with chlorinated polyethylene samples containing 48 and 42% by weight of chlorine. Chlorinated polyethylene with a lower chlorine content was not miscible with PDPA. 相似文献
77.
and
provided a variety of
and
alkaloids as well as novel ring-opened indole alkaloids including leuconolam (6), rhazinilam (8) and 5,21-dihydrorhazinilam (9). Facile acid and base reactions of leuconolam lead to ring reclosure products. Physical and spectral data of norfluorocurarine (
), norfluorocurarine-Nb-oxide (
), eburnamine (2), kopsinine (5) and epileuconolam (7) as well as some derivatives of leuconolam are also provided. 相似文献
78.
79.
80.
Pyrolysis of 3,5-dimethyl-1-propynoylpyrazole (1) at 640°C/0.1 torr gives 2-methyl-1-pyrazolo[2,3-a]pyridin-5-one (3) with inversion of the propynoyl chain. 1-Ethynylpyrazole and tricarbon monoxide have been identified in pyrolysates formed at 700–1000°C/0.01–0.1 torr from the parent 1-propynoylpyrazole (4). 相似文献