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Ring Substitution (ring + substitution)

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Chemistry	100%

Selected Abstracts

ChemInform Abstract: Preparation of 4,5-Disubstituted Pyrimidines: Ring Substitution of 5-Mesyloxymethylpyrimidines.

CHEMINFORM, Issue 19 2001
Howard Sard
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Catalytic kinetics of quaternary ammonium poly(styrene- co -methylstyrene) resin

AICHE JOURNAL, Issue 7 2006
Ho-Shing Wu
Abstract The catalytic kinetics and synthesis of poly(styrene- co -chloromethylstyrene) resin of different degrees of crosslinkages and ring substitutions were investigated by copolymerizing styrene and chloromethylstyrene through crosslinking with divinylbenzene. Poly(styrene- co -chloromethylstyrene) quaternary ammonium salt was obtained with activating poly(styrene- co -chloromethylstyrene) resin with tertiary amine. More than 20 types of poly(styrene- co -chloromethylstyrene) quaternary ammonium catalyst were prepared, with reaction conditions including immobilized time (0.125,4 days), concentration of tertiary amine (0.1,2 kmol/m3), kinds of solvents in immobilization (methanol, ethyl alcohol, and DMF), and kinds of tertiary amines (trimethylamine, triethylamine, tripropylamine, tri- n -butylamine, tri- n -pentylamine, tri- n -hexylamine, and tri- n -octylamine). These catalysts were used to achieve the optimum allylation of phenol. The reactions were conducted and studied individually with either equal mole or equal weight of catalyst. The best reactivity for the allylation of phenol was obtained when the structure of the quaternary ammonium catalyst was 10% degree of ring substitution and 2% degree of crosslinkage activating with trihexylamine. The turnover number and the effectiveness factor were also calculated. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

29Si,13C spin,spin couplings over Si,O,Carom link

MAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2006
Jan Sýkora
Abstract 29Si,13C couplings were measured in para substituted silylated phenols, XC6H4OSiR1R2R3(X 2, CF3, Cl, F, H, CH3, CH3O). The SiR1R2R3 silyl groups included trimethylsilyl (Si(CH3)3, TMS), tert- butyldimethylsilyl (Si(CH3)2C(CH3)3, TBDMS), dimethylsilyl (SiH(CH3)2, DMS), and tert- butyldiphenylsilyl (Si(C6H5)2C(CH3)3, TBDPS). Previously developed (Si,C,Si)gHMQC methods and narrow 29Si lines allowed the determination of coupling constants over up to five bonds. Besides the number of intervening bonds between the silicon and carbon atoms, all the measurable couplings depend also on the nature of the substituents on the silicon. The two- and three-bond couplings are not affected by ring substitution in the para position. These properties render the 29Si,13C couplings suitable for line assignment in the spectra of silylated polyphenols. The experimental results are in reasonable agreement with theoretical calculations. The calculations show, in agreement with the data reported in the literature for couplings between other nuclei, that the two-bond and three-bond couplings, which are of similar magnitudes, are of opposite signs. If the signs of these geminal and vicinal couplings could be determined experimentally, they would greatly facilitate the line assignment. The four- and five-bond couplings are affected by the substituent X in a nontrivial manner. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Structure,Activity Relationships of SSAO/VAP-1 Arylalkylamine-Based Substrates

CHEMMEDCHEM, Issue 4 2009
Francesc Yraola Dr.
Abstract SSAO/VAP-1 substrates may be valuable for the treatment or prevention of diabetes mellitus, as they show insulin-mimetic properties. This review highlights the importance of studying the relevant steric and electronic features in the development of new ligands with better SSAO/VAP-1 recognition, enhanced selectivity over other amine oxidases, and improved metabolic behavior. Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1) substrates show insulin-mimetic effects and are therefore potentially valuable molecules for the treatment of diabetes mellitus. Herein we review several structural and electronic aspects of SSAO arylalkylamine-based substrates. Two main modifications directly affect amine oxidase (AO) activity: 1),variation in ring substitution modulates the biological activity of the arylalkylamine ligand by converting a substrate into a substrate-like inhibitor, and 2),variation in the number of methylene units between the aromatic ring and the ammonium groups of the arylalkylamine substrates dramatically alters the oxidation rate between species. Furthermore, we review relevant information about mammalian SSAO/VAP-1 substrate selectivity and specificity over monoamine oxidases (MAOs). [source]