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61.
62.
Samer Saleh 《Tetrahedron》2009,65(34):7146-1075
High-yield alkynylations are successfully achieved by a simple and widely accessible catalytic system for an unprecedented variety of heterocyclic bromides and chlorides in position -2, -3 or -5: pyridine, quinoline, thiophene, furan, thiazole, benzothiazole, pyrimidine, pyridazine, pyrazine, dioxepin halides are efficiently functionalized in short time reactions. This copper-free methodology employs 1 mol % palladium only, with inexpensive PPh3 and amine base. The ionic liquid solvent allows a straigtforward separation of products and recycling opportunity. Unsuitable substrates and secondary reactions are also reported in order to point out further progress in cross-coupling using ionic liquids. 相似文献
63.
We present algorithms for the propositional model counting problem #SAT. The algorithms utilize tree decompositions of certain graphs associated with the given CNF formula; in particular we consider primal, dual, and incidence graphs. We describe the algorithms coherently for a direct comparison and with sufficient detail for making an actual implementation reasonably easy. We discuss several aspects of the algorithms including worst-case time and space requirements. 相似文献
64.
Samer Al Akhrass Denis Damiron Géraldine Carrot Eric Drockenmuller 《Journal of polymer science. Part A, Polymer chemistry》2010,48(17):3888-3895
Random copolymers of styrene, p‐azidomethylstyrene and 1H,1H,2H,2H‐perfluorodecyl methacrylate were prepared in two steps involving nitroxide‐mediated radical copolymerization and azidation reaction and further characterized by 1H and 19F NMR, size exclusion chromatography, differential scanning calorimetry, and thermal gravimetric analysis. Ultrathin films of these azidomethyl‐functionalized fluorinated random copolymers, with thicknesses ranging from 20 to 100 nm, were spin coated onto Si substrates and then crosslinked by ultraviolet irradiation resulting in smooth and insoluble crosslinked fluorinated polymer mats. The surface properties of the supported thin films were investigated by X‐ray photoelectron spectroscopy and water contact angle measurements. These tailored photo‐crosslinked coatings afford a versatile control and homogenization of the wetting properties of different organic and inorganic substrates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3888–3895, 2010 相似文献
65.
Samer Israwi 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(1):81-93
We consider here the 1D Green-Naghdi equations that are commonly used in coastal oceanography to describe the propagation of large amplitude surface waves. We show that the solution of the Green-Naghdi equations can be constructed by a standard Picard iterative scheme so that there is no loss of regularity of the solution with respect to the initial condition. 相似文献
66.
Protocols for solid-phase syntheses of soluble peptidyl phosphoranes are presented. Various supported phosphoranylidene acetates were prepared on Rink amide or via alkylation of trialkyl- and triarylphosphines with bromoacetyl Wang ester. C-Acylation was conducted racemization-free with activated Fmoc-amino acids, followed by SPPS (solid-phase peptide synthesis). Acidic conditions released decarboxylated peptidyl phosphoranes into solution. The protocol allowed for the electronic variation of peptidyl phosphoranes which were investigated in ligation reactions with azides in organic and aqueous solvents. 相似文献
67.
On robust optimization of two-stage systems 总被引:2,自引:0,他引:2
Robust-optimization models belong to a special class of stochastic programs, where the traditional expected cost minimization objective is replaced by one that explicitly addresses cost variability. This paper explores robust optimization in the context of two-stage planning systems. We show that, under arbitrary measures for variability, the robust optimization approach might lead to suboptimal solutions to the second-stage planning problem. As a result, the variability of the second-stage costs may be underestimated, thereby defeating the intended purpose of the model. We propose sufficient conditions on the variability measure to remedy this problem. Under the proposed conditions, a robust optimization model can be efficiently solved using a variant of the L-shaped decomposition algorithm for traditional stochastic linear programs. We apply the proposed framework to standard stochastic-programming test problems and to an application that arises in auctioning excess electric power.
Mathematics Subject Classification (1991):90C15, 90C33, 90B50, 90A09, 90A43Supported in part by NSF Grants DMI-0099726 and DMI-0133943 相似文献
68.
Raid J. Abdel-Jalil Monther Khanfar Kayed Abu-Safieh Samer Al-Gharabli Mustafa El-Abadelah Wolfgang Voelter 《Monatshefte für Chemie / Chemical Monthly》2005,40(7):619-624
A simple high-yielding procedure is presented for the synthesis of pyrazolopyrimidinones overcoming limitations found in earlier work and of considerable utility for the production of intermediates for potential phosphodiesterase inhibitors. 相似文献
69.
Arafat SN Dutta S Perring M Mitchell M Kenis PJ Bowden NB 《Chemical communications (Cambridge, England)》2005,(25):3198-3200
Mild methods to assemble well-ordered organic monolayers of olefins on Si(111) using 2,2,6,6-tetramethyl-1-piperidinyloxy and to pattern these monolayers on the micrometer-size scale using soft lithography are reported. 相似文献
70.
Jason R. Besse Samuel L. Chasen Tristan R. Claborn April N. Collins Abigail E. Darpel Anna Fatta Ramy W. Ghanim Ghady E. Kanaan Alexandr Lukyanchuk Taylor L. Nelson Jessica L. Ray Alexis L. Smith James D. Spagnola Sarah A. Veazey Logan H. Womack Michael D. Wells Nabin Panth Sean Parkin Mark D. Watson 《Journal of polymer science. Part A, Polymer chemistry》2022,60(12):1918-1923
Nucleophilic aromatic substitution (SNAr) reactions are exploited to prepare poly(arylene sulfide)s (PAS's) via the reaction of bis-thiolates and dibrominated pyromellitic diimide (PMDI) derivatives. Small-molecule model studies reveal the reaction is well-defined and proceeds in quantitative yield in practical times at room temperature. Variation in comonomer feed ratios allowed some control over target polymer molecular weights in the step polymerization, but control was likely limited by the relatively poor polymer solubility in the dipolar aprotic solvents typically employed to promote SNAr reactions. One substitution pattern produces a steric “pocket” around the PMDI units, inducing a peculiar solubility trend in halogenated solvents; that is, greatly reduced solubility in CHCl3 relative to CH2Cl2 and C2H2Cl4. One example small-molecule readily dissolves in CHCl3 at room temperature, then rapidly grows poorly soluble crystals revealed by single-crystal XRD to contain CHCl3 molecules in the steric pockets. Finally, the recently demonstrated depolymerization of phthalonitrile-based PAS's via ipso substitution with monothiolates as chain scission agents yields quantitative molecular weight reduction to monomeric species from the polymers reported here. 相似文献