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61.
P. Veeraraghavan Ramachandran Michael T. Rudd M. Venkat Ram Reddy 《Tetrahedron letters》2005,46(15):2547-2549
Alkyl propiolate couples with itself in the presence of catalytic DABCO under very mild conditions to provide a quantitative yield of E-hex-2-en-4-yne dioates. Hydrogenation of these enyne dioates using Lindlar catalyst provides the corresponding E,Z-diene dioate, a common structural motif found in an array of natural products. 相似文献
62.
Ramachandran PV Rudd MT Burghardt TE Ram Reddy MV 《The Journal of organic chemistry》2003,68(24):9310-9316
A modified hydroalumination protocol for the preparation of [alpha-(ethoxycarbonyl)vinyl]diisobutylaluminum and its beta-methyl or -phenyl analogues was developed. These vinylaluminum reagents react with aldehydes and ketones to provide the corresponding functionalized allyl alcohols in good to excellent yields. Perfluoroalkyl and -aryl carbonyl compounds, alpha-keto esters, alpha-acyl cyanides, and alpha-acetylenic ketones provide the corresponding alpha-hydroxyalkenes in high yields. The allyl alcohol product ratios from the vinylalumination of unsymmetrical alpha-diketones with [alpha-(ethoxycarbonyl)vinyl]diisobutylaluminum and its beta-methyl or -phenyl analogues depend on the steric and electronic environments of the ketones as well as the reagents. The products from the vinylalumination of alpha-bromoaldehydes and -ketones were cyclized with K2CO3 or KF under nonaqueous conditions to provide functionalized vinylepoxides in high yields. Vinylaluminations of keto-protected pyruvaldehyde provided the products, which were converted to alpha-alkylidene-beta-hydroxy-gamma-lactones. 相似文献
63.
Activated aryl halides undergo smooth nucleophilic substitution reactions with secondary amines in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) ionic liquids (ILs) at room temperature to afford the corresponding arylamines in excellent yields under mild and neutral conditions. 相似文献
64.
P. Giridhar Reddy A. Venkat Reddy A. Ratnamala S. Venkateswara Rao Sushama Kandlikar 《Reaction Kinetics and Catalysis Letters》1984,26(1-2):209-213
Kinetics of Ru(III) catalyzed oxidation of methanol, ethanol, n-propanol, n-butanol, isopropanol and iso-butanol by N-bromosuccinimide (NBS) in the presence of Hg(II) acetate have been studied in acid medium. The oxidation exhibits a fractional order in [alcohol] and first order in [NBS]. The applicability of Taft's equation was tested. The probable mechanism is discussed.
, , -, -, - () Hg(II), Ru(III), . . . .相似文献
65.
A new technique-crystallization in asymmetric microwells-generates arrays of small crystals with controlled size, orientation, and arrangement in space. These arrays of crystals can be generated in a form completely encapsulated in polymer. 相似文献
66.
Wu H Thalladi VR Whitesides S Whitesides GM 《Journal of the American Chemical Society》2002,124(48):14495-14502
This paper describes an approach to the fabrication of three-dimensional (3-D) structures of millimeter-scale spherical beads having a range of lattices-tetragonal, cubic, and hexagonal-using hierarchical self-assembly. The process has five steps: (i) metal-coated beads are packed in a rod-shaped cavity in an elastomeric polymer (poly(dimethylsiloxane), PDMS); (ii) the beads are embedded in a second polymer (PDMS or polyurethane, PU) using a procedure that leaves the parts of the beads in contact with the PDMS exposed; (iii) the exposed areas of the beads are coated with a solder having a low melting point; (iv) the polymer rods-with embedded beads and exposed solder drops-are suspended in an approximately isodense medium (an aqueous solution of KBr) and allowed to self-assemble by capillary interactions between the drops of molten solder; and (v) the assembly is finished by several procedures, including removing the beads from the polymer matrix by dissolution, filling the voids left with another material, and dissolving the matrix. The confinement of the beads in regular structures in polymer rods makes it possible to generate self-assembled structures with a variety of 3-D lattices; the type of the lattice formed can be controlled by varying the size of the beads, and the size and shape of the cross-section of the rods. 相似文献
67.
Mao C Thalladi VR Wolfe DB Whitesides S Whitesides GM 《Journal of the American Chemical Society》2002,124(49):14508-14509
This Communication describes a new strategy for the design of adaptive structures based on reconfigurable mesoscale self-assembly. Several sets of millimeter-scale objects have been designed that can self-assemble into two different, regular aggregates at the interface between an aqueous solution and perfluorodecalin; the choice between the two aggregates is determined by the density of the aqueous phase. 相似文献
68.
The results for the diffusivity of nanoparticles in unentangled semidilute polymer solutions obtained using coarse‐grained simulations are presented. The results indicate that for particle sizes smaller than the polymer radius of gyration, the nanoparticle diffusivities deviate from Stokes–Einstein predictions and depend explicitly on the polymer radius of gyration and the polymer solution correlation lengths. Scaling ideas proposed are invoked for rationalizing such noncontinuum effects and demonstrate that the simulation results could be collapsed onto a single universal function of the depletion thickness, the polymer radius of gyration, and the particle radius. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2145–2150. 相似文献
69.
S. Veeraswamy K. Indrasena ReddyR. Venkat Ragavan K. Tirumal ReddySatyanarayana Yennam A. Jayashree 《Tetrahedron letters》2012,53(35):4651-4653
β-Hydroxy ketones were synthesized in one-pot from β-diketones by reducing alkyl ketones chemoselectively by keeping aryl ketone intact. Initially, β-diketones were enolized using LiHMDS and later alkyl ketone was chemoselectively reduced efficiently by lithium aluminium hydride. This method produces β- hydroxyl ketones from the corresponding β-diketones in high yield. 相似文献
70.
The problem of reconstruction of a binary image in the field of discrete tomography is a classic instance of seeking solution applying mathematical techniques. Here two such binary image reconstruction problems are considered given some numerical information on the image. Algorithms are developed for solving these problems and correctness of the algorithms are discussed. 相似文献