نتایج جستجو برای: alternative substituents

تعداد نتایج: 311992  

M Daghighi Asl P Makkipour R Ghiasi S Azmayesh

Abstract: Systematic studies on the substituent effect in para substituted Fe(CO)4–pyridine complexes have been studied on the basis of DFT quantum-chemical calculations. The following substituents were taken into consideration: NO2, CN, CHO, F, H, CH3, and OH. Additionally, the Fe–N and Fe–C bonds were characterized on the basis of Atoms in Molecules topological analysis of electron density. I...

Journal: :Chemical science 2017
Jevgenijs Tjutrins Bruce A Arndtsen

We describe here a tandem catalytic route to prepare imidazoles in a single operation from aryl iodides, imines and CO. The reaction involves a catalytic carbonylation of aryl halides with imines to form 1,3-dipoles, which undergo spontaneous 1,3-dipolar cycloaddition. Overall, this offers an alternative to coupling reactions to construct the (hetero)aryl-imidazole motif, where variation of the...

2017
Jevgenijs Tjutrins Bruce A. Arndtsen

We describe here a tandem catalytic route to prepare imidazoles in a single operation from aryl iodides, imines and CO. The reaction involves a catalytic carbonylation of aryl halides with imines to form 1,3dipoles, which undergo spontaneous 1,3-dipolar cycloaddition. Overall, this offers an alternative to coupling reactions to construct the (hetero)aryl-imidazole motif, where variation of the ...

2011
Krzysztof Brzezinski Piotr Wałejko Aneta Baj Stanisław Witkowski Zbigniew Dauter

The crystal structure of the title compound, C(28)H(38)O(11), solved and refined against synchrotron diffraction data, contains two formula units in the asymmetric unit. In both mol-ecules, the dihydro-pyran ring along with its methyl substituents is disordered and adopts two alternative half-chair conformations. The occupancy of the major conformers of the two mol-ecules refined to 0.858 (5) a...

2008
Kerstin Höhfeld Andreas Teckentrup Timothy Clark

Scaffolds are defined as the core structure of a molecule connecting different substituents or functional groups. Defining bioisosteric alternative scaffolds for lead structures is an important task in drug design to improve e.g. the activity, bioavailability or selectivity of the structures concerned [1]. In this context, bioisosteric replacement means changing the scaffold structure while ret...

Journal: :Chemical communications 2013
Srimanta Manna Sandipan Jana Tapish Saboo Arun Maji Debabrata Maiti

Nitroolefins are usually synthesized using the Henry reaction. Here we report an alternative metal-free decarboxylative nitration protocol for the preparation of the nitroolefins from α,β-unsaturated carboxylic acids using t-butylnitrite (t-BuONO) and TEMPO. α,β-Unsaturated carboxylic acids bearing β-aromatic and β-heteroaromatic substituents gave (E)-nitroolefins exclusively under mild conditi...

2014
M.Kh. Dzhafarov

The attention is focused on the main classes of anthelmintics. Mode of action of the anthelmintics and the anthelmintic resistance, and alternative methods for dehelminthization are discussed. A targeted search for new anthelmintic substances in the series of speculative parental hydrocarbons (benzene, indene, naphthalene, 1 H1-cyclopenta [a]-naphthalene and phenanthrene) is suggested to be pro...

2009
D. C. Peets D. G. Hawthorn Ruixing Liang D. A. Bonn W. N. Hardy

X-ray absorption spectroscopy on oxygen-annealed, self-flux-grown single crystals of Tl2Ba2CuO6+δ suggests a microscopic doping mechanism whereby interstitial oxygens are attracted to copper substituted on the thallium site, contributing holes to both the planes and to these coppers, and typically promoting only one hole to the plane rather than two. These copper substituents would provide an i...

Journal: :iranian journal of chemistry and chemical engineering (ijcce) 1999
daryoush mohajer mojtaba bagherzadeh

the epoxidation of olefins with tetra n-butylammonium periodate, n-bu4/nio4, is catalyzed by six different tetrakis (4-substituted phenyl) porphyrinatomanganese(iii) acetate, mn(t4-xpp)oac, complexes in the presence of imidazole as an axial ligand with low to high yields and complete selectivity at room temperature. while the electronic effects of the highly electron-withdrawing no2 substituent...

2017
Elzbieta Sochacka Elzbieta Lodyga-Chruscinska Justyna Pawlak Marek Cypryk Paulina Bartos Katarzyna Ebenryter-Olbinska Grazyna Leszczynska Barbara Nawrot

Modified nucleosides present in the wobble position of the tRNA anticodons regulate protein translation through tuning the reading of mRNA codons. Among 40 of such nucleosides, there are modified uridines containing either a sulfur atom at the C2 position and/or a substituent at the C5 position of the nucleobase ring. It is already evidenced that tRNAs with 2-thiouridines at the wobble position...

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