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Now showing items 33 - 48 of 86129

  • A Tribute to William N. Gill

    Plawsky, Joel L.   Subramanian, R. Shankar  

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  • N–N bond cleavage in diazoalkanes with a titanium alkylidene

    Ito, Jun-ichi   Crestani, Marco G.   Bailey, Brad C.   Gao, Xinfeng   Mindiola, Daniel J.  

    The titanium alkylidene-triflate complex (PNP)Ti=(CHBu)-Bu-t(OTf) was found to promote N-N bond cleavage of 9-diazofluorene and ditolyldiazomethane to give the imido complexes, (PNP)Ti=N[C13H9](OTf) (1) and (PNP)Ti=N[CHtolyl(2)](OTF) (2), respectively. The molecular structure of 2 was determined by single-crystal X-ray diffraction studies. Along with imido formation leading to 1 and 2, the alkylidene Ti=(CHBu)-Bu-t ligand in (PNP)Ti=(CHBu)-Bu-t(OTf) was found to eliminate with the alpha-N atom of the diazoalkane to form the nitrile (NCBu)-Bu-t, which was confirmed by a combination of H-1 NMR spectroscopy and GC-MS. The reaction mechanism of the N-N bond cleavage promoted by the reactive Ti=(CHBu)-Bu-t ligand is also discussed. (C) 2014 Elsevier Ltd. All rights reserved.
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  • A note on the (∞,n)–category of cobordisms

    Calaque, Damien   Scheimbauer, Claudia  

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  • Enantioselective Total Synthesis of Altersolanol A and N

    Mechsner, Bastian   Böse, Dietrich   Hogenkamp, Fabian   Ledermann, Nadia   Hartmann, Rudolf   Bochinsky, Kevin   Frey, Wolfgang   Pietruszka, Jörg  

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  • A counterexample to Stein’s Equi-$n$-square Conjecture

    Pokrovskiy, Alexey   Sudakov, Benny  

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  • A Disk-Type Polyarene Containing Four B←N Units

    Liu, Jun   Min, Yang   Dou, Chuandong   Tian, Hongkun   Wang, Lixiang  

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  • Gülsün Karamustafa: A Life of Care

    Kortun, Vasif  

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  • #Me(n)Too: Storying a Male-on-Male Sexual Assault

    Purnell, David  

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  • On the fractional parts of a(n)/n

    Cilleruelo, Javier   Kumchev, Angel   Luca, Florian   Rue, Juanjo   Shparlinski, Igor E.  

    We give various results about the distribution of the sequence {a(n)/n}(n >= 1) modulo 1, where a >= 2 is a fixed integer. In particular, we find an explicit infinite subsequence A such that {a(n)/n}(n is an element of A) is uniformly distributed modulo 1. Also we show that for any constant c > 0 and a sufficiently large N, the fractional parts of the first N terms of this sequence hit every interval subset of [0, 1] of length vertical bar vertical bar >= c N-0.475.
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  • A structural study of N,N′-bis-aryl-N′′-acylguanidines

    O\"Donovan, Daniel H.   Kelly, Brendan   Diez-Cecilia, Elena   Kitson, Martin   Rozas, Isabel  

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  • A Journey of the Vocal Iso(n)

    Moody, Ivan  

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  • A structural study of N,N '-bis-aryl-N ''-acylguanidines

    O'Donovan, Daniel H.   Kelly, Brendan   Diez-Cecilia, Elena   Kitson, Martin   Rozas, Isabel  

    The N-aryl- and N-acylguanidine structural motifs are essential for the function of several important classes of molecules, including pharmaceuticals, catalysts and natural products. Compounds combining both motifs can exist as different isomers due to tautomerism within the guanidine subunit, E/Z isomerism with reference to the guanidine double bond, and conformational isomerism. This complex phenomenon results in unresolved broad signal NMR spectra that strongly complicate the characterisation of these derivatives. Hence, the present study examines isomerism in N,N'-bis-aryl-N ''-acylguanidines using low temperature NMR spectroscopy in tandem with Density Functional Theory (DFT), Natural Bond Analysis (NBO) and the Gauge-Invariant Atomic Orbital (GIAO) approach for calculating the NMR chemical shifts associated with each isomer. It was found that the structural preference of these compounds is strongly influenced by intramolecular hydrogen bond (IMHB) effects.
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  • Terretonin N: A New Meroterpenoid from Nocardiopsis sp.

    Hamed, Abdelaaty   Abdel-Razek, Ahmed S.   Frese, Marcel   Stammler, Hans Georg   El-Haddad, Atef F.   Ibrahim, Tarek M. A.   Sewald, Norbert   Shaaban, Mohamed  

    Terretonin N (1), a new highly oxygenated and unique tetracyclic 6-hydroxymeroterpenoid, was isolated together with seven known compounds from the ethyl acetate extract of a solid-state fermented culture of Nocardiopsis sp. Their structures were elucidated by spectroscopic analysis. The structure and absolute configuration of 1 were unambiguously determined by X-ray crystallography. The isolation and taxonomic characterization of Nocardiopsis sp. is reported. The antimicrobial activity and cytotoxicity of the strain extract and compound 1 were studied using different microorganisms and a cervix carcinoma cell line, respectively.
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  • Uplifting GPPZ: a ten-dimensional dual of N=3D1*

    Bobev, Nikolay   Gautason, Fridrik Freyr   Niehoff, Benjamin E.   van Muiden, Jesse  

    We find a new supersymmetric solution of type IIB supergravity which is the uplift of the GPPZ solution of maximal SO(6) gauged supergravity in five dimensions. This background is expected to be holographically dual to an N =3D 1* supersymmetric mass deformation of four-dimensional N =3D 4 SYM. The ten-dimensional solution is singular in the region corresponding to the IR regime of the dual gauge theory and we discuss the physics of the singularity in some detail.
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  • Almost Partitioning a 3-Edge-Colored $K_{n,n}$ into Five Monochromatic Cycles

    Lang, Richard   Schaudt, Oliver   Stein, Maya  

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  • Uplifting GPPZ: a ten-dimensional dual of N=1∗$$ \mathcal{N}={1}^{\ast } $$

    Bobev, Nikolay   Gautason, Friðrik Freyr   Niehoff, Benjamin E.   van Muiden, Jesse  

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