Sang Yong Pyun

Polymeric nickel(II) and copper(II) complexes with btc2− ions as bridging ligands (btc2−=1,2,4,5-benzenetetracarboxylic acid dianion)

Abstract Two new complexes of composition {[ Ni ( L )( btc 2− )]·2 H 2 O } n (1) {L=1,4,8,11-tetraazacyclotetradecane} and {[ Cu ( L )( btc 2− )]· H 2 O } n (2) were obtained by reacting [ Ni ( L )]·2 ClO 4 or [ Cu ( L )]·2 ClO 4 and btc, and their structures were determined by analytical, spectroscopic, and X-ray diffraction methods. The blue complex 1 and violet complex 2 consist of 1D polymeric chains with nickel(II) or copper(II) macrocycles and bridging btc2− ligands, respectively. In 1 the COO− groups on the 1,4-positions of the btc2− ligand are coordinated to the central nickel(II) atom, but in 2 the COOH groups on the 1,5-positions of the btc2− ligand are involved in interacting with the central copper(II) atom through an unusual carbonyl coordination.

Phosphorylated glucosamine inhibits the inflammatory response in LPS-stimulated PMA-differentiated THP-1 cells

This study evaluated the effect of phosphorylated glucosamine (pGlc) on the regulation of cytokines involved in immunological activities. Changes in the inflammatory profiles of lipopolysaccharide (LPS)-stimulated phrobol 12-myristate 13-acetate (PMA)-differentiated THP-1 macrophage models were investigated following pGlc treatment. Treatment with pGlc inhibited the production of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6). In addition, pGlc suppressed the regulation of inflammatory mediators such as TNF-alpha, IL-1beta, IL-6, inducible NO synthase (iNOS), and cyclooxygenase-2 (COX-2) in LPS-stimulated THP-1 macrophages. Furthermore, we confirmed that the LPS-stimulated transcription of MAP kinases in PMA-differentiated THP-1 macrophages was inhibited by pGlc. According to this study, pGlc can be considered as a potential anti-inflammatory agent.

Synthesis and Photopolymerization of Vinyl Ether and Epoxy-Functionalized Silicones

The reactive precursors, vinyl ethers, and epoxy-silicones, were synthesized. The vinyl ether monomers were prepared from primary alcohol and ethyl vinyl ether with mercury (II) acetate. The epoxy-functionalized silicones have been achieved by the controlled, rhodium-catalyzed, chemoselective hydrosilation of vinyl ether with siloxanes or silane. It was shown that the hydrosilation proceeds exclusively at the vinyl ether group of alkenyl vinyl ether without participation at the alkenyl group. The photoinduced cationic polymerization of these monomers was studied and found to be all highly reactive.

Elimination reactions of (E)-2,4-dinitrobenzaldehyde O-benzoyloximes promoted by R2NH/R2NH2 + in 70 mol % MeCN(aq). Change of reaction mechanism

Elimination reactions of (E)-2,4-(NO(2))(2)C(6)H(3)CHNOC(O)C(6)H(4)X (1) promoted by R(2)NH/R(2)NH(2)(+) in 70 mol % MeCN(aq) have been studied kinetically. The reactions are second-order and exhibit Bronsted beta = 0.27-0.32 and |beta(lg)| = 0.28-0.32. The result can be described by a negligible p(xy) interaction coefficient, p(xy) = partial differential beta/partial differential pK(lg) = partial differential beta(lg)/partial differential pK(BH) approximately = 0, which describes the interaction between the base catalyst and the leaving group. The negligible p(xy) coefficients are consistent with the (E1cb)(irr) mechanism.

Eliminations from aryl bis(p-chlorophenyl)acetates promoted by R2NH in MeCN. Effects of base-solvent and β-aryl group

Elimination reactions of (4′-ClC6H4)2CHCO2C6H3-2-X-4-NO2 promoted by R2NH in MeCN have been studied kinetically. The observed second-order kinetics, Brønsted β = 0.44–0.86 and |βblog| = 0.46–0.69 are consistent with the E2 mechanism. The Brønsted β decreased as the leaving group was made more nucleofugic and the |βlog| increased with a weaker base. Comparison with existing data reveals that the structure of the transition state is relatively insensitive to the base-solvent and β- aryl substituent on the E2 transition state.

Kinetic studies on the addition of phenol to S-phenyl-S-vinyl-N-p-tosylsulfilimine derivatives

The rate constants of nucleophilic addition of phenyl to vinylsulfilimine(VSI) and its derivatives were determined by an ultraviolet spectrophotometer at 25°C, and the rate equations which can be applied over a wide pH range were obtained. On the basis of the pH-rate profile, product analysis, general base catalysis, and the substituent effect, a plausible mechanism of this addition reaction was proposed: Below pH 3.0, the reaction proceeded via the addition of a neutral molecule to the carbon-carbon double bond after protonation at the nitrogen atom of the sulfilimine. Above pH 10.0, the addition of a phenoxide ion to the carbon-carbon double bond was rate controlling. However, in the pH range of 3.0 to 10.0, these two reactions occurred competitively.

Mechanism of the hydrolysis of α-(p-nitrophenyl)cinnamonitrile derivatives

The rate constant hydrolysis of α-(p-nitrophenyl)cinnamonitrile(NCPN) and its derivatives have been determined at various pH, and the rate equation which can be applied over a wide pH range is obtained. On the basis of the rate equation, hydrolysis product, general base, and substituent effects, a plausible mechanism of hydrolysis has been proposed: At pH < 4.0, the hydrolysis was initiated by the addition of water to β-carbon of the carbon-carbon double bond. At pH > 8.5, the addition of hydroxide ion to the double bond was rate controlling. In the range of pH 4.0–8.5, these two reactions occurred competitively.