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Ketene-forming elimination from C4H3(O)CH2C(O)OC6H3-2-X-4-NO2 (1) promoted by R2NH in MeCN has been studied. The reactions produced elimination products and exhibited second-order kinetics with Bronsted β = 0.51, and |βlg| = 0.47–0.53, indicating that the reaction proceeds by the E2 mechanism via an E2-central transition state. Comparison of β, |βlg|, ΔH≠, and ΔS≠ values for R2NH-promoted eliminations from ArCH2C(O)OC6H3-2-X-4-NO2 reveals that the transition-state structures for Ar = furyl and thienyl are similar and more symmetrical than that for Ar = Ph. This outcome has been attributed to the greater double bond stabilizing ability of the former than that of the latter.

Elimination reactions of (E)-2,4,6-(NO2 ) 3C6H2CHNOC(O)C6H4X (3) promoted by R2NH/R2NH2 + in 70 mol% MeCN (aq) have been studied. The reactions produced elimination products and exhibited second-order kinetics. The β and |βlg| values remained nearly the same for all leaving groups and bases. The results can be described by the negligible pxy interaction coefficient, pxy = ∂β/∂pK lg = ∂βlg/∂pK BH ≈ 0, which provides a strong support for the (E1cb)irr mechanism. For eliminations from (E)-ArCHNOC(O)C6H4X (1, 3) and (E)-2,4,6-(NO2)3C6H2CHNOAr′ (2, 3), the change of the β-aryl group (Ar) from 2,4-dinitrophenyl (1) to 2,4,6-trinitrophenyl (3) increased the rate by 270-fold without appreciable change in the transition state structure. On the other hand, the leaving group (OAr′) variation from benzoate (3) to 4-nitrophenoxy (2) induced a change in reaction mechanism from (E1cb)irr to E2. These results have been attributed to the cyclic transition state for the nitrile-forming eliminations involving the benzoate leaving group.

Nucleophilic substitution reactions of 5-XC4H2 (S)C(O)OC6H3 -2-Y-4-NO2 (1) promoted by 4-Z-C6H4O −/4-Z-C6H4OH in 20 mol % dimethyl sulfoxide (DMSO)(aq) have been studied kinetically. The reactions exhibited second-order kinetics with βacyl = −2.52 to −2.83, ρ(x) = 2.81–3.16, βnuc = 0.88–0.04 and βlg = −0.94, respectively. The results have been interpreted with an addition–elimination mechanism in which the nucleophilic attack occurs in the rate-determining step. Comparison with existing data reveals that the rate-determining step changes from the second to the first step by the change in the nucleophile from R2NH/R2NH2 + to 4-Z-C6H4O −/4-Z-C6H4OH.

the effect of the β-aryl group on the ketene-formingelimination was assessed.Key Words : Elimination, E2 and E1cb Mechanism, β–Aryl Group effectIntroductionExtensive studies of the structure-reactivity relationshipsin the ketene-forming elimination reactions have led to thequalitative understanding of the relationship between thereactant structure and the mechanism.

value increased with a stronger electron-withdrawing 5-thienyl substituent, the Hammett plots arelinear except for X = MeO, and Yukawa-Tsuno plots are linear with ρ = 0.79-1.32 and r = 0.28-0.93,respectively. The ρ value increased and r value decreased with a stronger nucleophile, indicating an increase inthe electron density at the C=O bond and a decrease in the resonance demand. These results have beeninterpreted with enhanced N-C bond formation in the transition state with the reactivity increase. Key Words : Aminolysis, Bronsted-type plot, Hammett plot, Yukawa-Tsuno plot IntroductionExtensive studies of the structure-reactivity relationshipsin the acyl transfer reactions from XC

Elimination reactions of (E)-2,4-(NO2)2C6H2CH=NOC6H3-2-X-4-NO2 (1a-e) promoted by R3N/R3NH + in 70 mol % MeCN(aq) have been studied kinetically. The reactions are second-order and exhibit Bronsted β = 0.800.84 and |βlg| = 0.39-0.42, respectively. For all leaving groups and bases employed in this study, the β and |βlg| values remained almost the same. The results can be described by a negligible pxy interaction coefficient, pxy = ∂β/pKlg = ∂βlg/pKBH ≈ 0, which describes the interaction between the base catalyst and the leaving group. The negligible pxy interaction coefficient is consistent with the (E1cb)irr mechanism. Change of the base-solvent system from R3N/MeCN to R3N/R3NH + -70 mol % MeCN(aq) changed the reaction mechanism from E2 to (E1cb)irr. Noteworthy was the relative insensitivity of the transition state structure to the reaction mechanism change.

The transition state was shifted toward theE1cb corner by an electron-withdrawing β-aryl substituentand toward the E1 intermediate and the product by astronger base in the reaction coordinate diagram. On theother hand, when the leaving group was changed from 2,4-dinitrophenoxide to picrate, the ρ value decreased but the βvalue increased. The results are in conflict with the predic-tion of the reaction coordinate diagram because both ρ and βvalues should be decreased with a better leaving group. Theunusual changes in the transition-state structure noted withthe leaving group variation have been interpreted as result-ing from a large difference in the anion-stabilizing ability ofthe leaving groups. However, the validity of this interpreta-tion remains to be verified. To determine whether a change in mechanism could berealized by introducing an even more electron-withdrawingβ-aryl substituent, we have now studied the reactions of ( E)-2,4-dinitrobenzaldehyde O-aryloxime with R

Inhibition of adipogenesis and lipid accumulation has a very crucial role to prevent obesity. Low molecular weight (LMW) chitosan is known to inhibit fat accumulation and adipogenesis. (N,O)-sulfated chitosan is a sulfation derivative of chitosan oligomers, and its anti-obesity effect is not yet reported. In this study, it has been reported that (N,O)-sulfated chitosan significantly decreased lipid accumulation, an indicator for adipogenesis, in differentiating 3T3-L1 preadipocyte cells. Furthermore, mRNA expressions and protein levels of key adipogenic markers such as peroxisome prolifetor-activated receptor (PPAR)-γ and CCAAT-enhancer binding protein (C/EBP)-α were considerably decreased by (N,O)-sulfated chitosan treatment. As a consequence, sulfation of LMWC remarkably increased its effect of adipogenesis inhibition, adding (N,O)-sulfated chitosan high potential to be utilized as a bioactive agent in food and pharmaceutical industry.

Nitrile-forming eliminations from (1) promoted by in 70 mol % MeCN(aq) have been studied kinetically. When X = , the reactions exhibited second-order kinetics as well as Brnsted = 0.63 and = 0.34-0.46, and an E2 mechanism is evident. As the leaving group was made poorer (X = H, Cl, and ), Brnsted value increased from 0.63 to 0.85-0.89 without much change in the value E2, indicating that structure of the transition state changed to an E1cb-like with extensive bond cleavage, significant negative charge development at the -carbon, and limited -OAr bond cleavage.

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.

A combination of a strong electron-withdrawing β-aryl group and anion-solvating protic solvent was required for the mecha-nistic change.We were interested in learning if a change to the E1cB mechanism could be realized in aprotic solvent by making the β-aryl group even more electron-withdrawing. To explore such possibility, we have now studied the reactions of (

Novel polymer electrolyte membranes containing the sulfonic acid groups attached on polymer backbone and side group simultaneously were synthesized. The bromo-poly(2,6-dimethyl-1,4-phenylene oxide)-co-(2,6-diphenyl-1,4-phenylene oxide) copolymer (BrcoPPO) was prepared by oxidative coupling polymerization with 2,6-dimethyl phenol, 2,6-diphenyl phenol, CuCl(I) and pyridine, and followed by bromination with bromine. Copolymer was maintained in 2,6-diphenyl phenol 10 mol% and 2,6-dimethyl phenol 90 mol%. Sulfonation of BrcoPPO (S-BrcoPPO) was carried out in a chlorobenzene solvent using chlorosulfonic acid. The polymeric membranes were cast from dimethylsulfoxide solution. The membranes were studied by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. S-BrcoPPO membranes exhibited proton conductivities from 2.3 × 10−3 to 1.4 × 10−2 S/cm, water uptake from 7.00 to 49.43%, IEC from 0.58 to 1.38 mequiv./g, methanol permeability from 1.9 × 10−7 to 3.5 × 10−7 cm2/S.

Elimination reactions of (4′-ClC6H4)2CHCO2C6H3-2-X-4-NO2 promoted by R2NH in MeCN have been studied kinetically. The observed second-order kinetics, Bronsted β = 0.44–0.86 and |βblog| = 0.46–0.69 are consistent with the E2 mechanism. The Bronsted 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.

The polymerization reaction of 4-[(n-butylsulfinyl)methyl]-4'-(chloromethyl)benzene (1a) with t-BuONa in CH 2 Cl 2 /monomethylformamide (MMF) (4/6) was studied kinetically. The reaction proceeds in two steps; the formation of a p-quinodimethane intermediate (M) followed by the polymerization of M. Results of kinetic studies and H-D exchange experiments reveal that the 1,6-elimination proceeds by the (Elcb)i rr mechanism. The rate of the disappearance of M was increased by the carbanion and S 2 O 8 2- , inhibited by TEMPO and unaltered by the addition of HCl. From these results, a free radical polymerization mechanism is proposed.

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.

Two new copper(II) complexes, Cu(L1)(ClO4)2 (1), {[(μ-oxalate)Cu(L1)] · 5H2O}n (2), and a zinc(II) complex, {[(μ-oxalate)Zn(L2)] · 3H2O · 0.5DMF}n (3) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane), have been synthesized and characterized by X-ray crystallography. In 1, the ligand conformation is planar, and the octahedral coordination about the copper(II) ion is completed by weakly interacting ClO 4 - ions. In 2 and 3, bridging oxalate ligands coordinate to copper(II) or zinc(II) ions in an unusually twisted bis-monodentate (trans-1,1′-bicoordination) mode. The rigidity and steric hindrance of macrocycles L1 and L2 by the introduction of two cyclohexane rings and methyl groups on a cyclam (1,4,8,11-tetraazacyclotetradecane) skeleton cause the bridging oxalate ligands to adopt such unusual geometries in 2 and 3.

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 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.

Ketene-forming eliminations from C4H3(S)CH2C(0)0-C6H3-2-X-4-N02 (1) promoted by R 2 NH in MeCN have been studied kinetically. The reactions are second-order and exhibit Bronsted β=0.51-0.62 and lβlgl= 0.47-0.53. Hence, an E2 mechanism is evident. The Bronsted β increased from 0.33 to 0.53 and |βlg| remained nearly the same by the change of the base-solvent from Bz(i-Pr)NH/Bz(i-Pr)NH 2 + in 70 mol% MeCN(aq) to Bz(i-Pr)NH-MeCN, indicating a change to a more symmetrical transition state with similar extents of Cβ-H and C α -OAr bond cleavage. When the /?-aryl group was changed from thienyl to phenyl in MeCN, the /? value increased from 0.53 to 0.73 and lβ lg l decreased from 0.53 to 0.43. This indicates that the transition state became skewed toward more Cβ-H bond breaking with less C α -OAr bond cleavage. Noteworthy is the greater double bond stabilizing ability of the thienyl group in the ketene-forming transition state.

Ketene-forming eliminations from C4H3(S)CH2C(O)O-C6H3-2-X-4-NO2 (1) promoted by R2NH in MeCN have been studied kinetically. The reactions are second-order and exhibit Bronsted β = 0.51-0.62 and |βlg| = 0.47-0.53. Hence, an E2 mechanism is evident. The Bronsted β increased from 0.33 to 0.53 and |βlg| remained nearly the same by the change of the base-solvent from Bz(i-Pr)NH/Bz(i-Pr)NH2 + in 70 mol% MeCN(aq) to Bz(i-Pr)NH-MeCN, indicating a change to a more symmetrical transition state with similar extents of Cβ-H and Cα-OAr bond cleavage. When the β-aryl group was changed from thienyl to phenyl in MeCN, the β value increased from 0.53 to 0.73 and |βlg| decreased from 0.53 to 0.43. This indicates that the transition state became skewed toward more Cβ-H bond breaking with less Cα-OAr bond cleavage. Noteworthy is the greater double bond stabilizing ability of the thienyl group in the ketene-forming transition state.

The cleavage of the diribonucleoside UpU (uridylyl-3'-5'-uridine) to form uridine and uridine (2',3')-cyclic phosphate catalyzed by the dinuclear Zn(II) complex of 1,3-bis(1,4,7-triazacyclonon-1-yl)-2-hydroxypropane (Zn(2)(1)(H(2)O)) has been studied at pH 7-10 and 25 degrees C. The kinetic data are consistent with the accumulation of a complex between catalyst and substrate and were analyzed to give values of k(c) (s(-)(1)), K(d) (M), and k(c)/K(d) (M(-)(1) s(-)(1)) for the Zn(2)(1)(H(2)O)-catalyzed reaction. The pH rate profile of values for log k(c)/K(d) for Zn(2)(1)(H(2)O)-catalyzed cleavage of UpU shows the same downward break centered at pH 7.8 as was observed in studies of catalysis of cleavage of 2-hydroxypropyl-4-nitrophenyl phosphate (HpPNP) and uridine-3'-4-nitrophenyl phosphate (UpPNP). At low pH, where the rate acceleration for the catalyzed reaction is largest, the stabilizing interaction between Zn(2)(1)(H(2)O) and the bound transition states is 9.3, 7.2, and 9.6 kcal/mol for the catalyzed reactions of UpU, UpPNP, and HpPNP, respectively. The larger transition-state stabilization for Zn(2)(1)(H(2)O)-catalyzed cleavage of UpU (9.3 kcal/mol) compared with UpPNP (7.2 kcal/mol) provides evidence that the transition state for the former reaction is stabilized by interactions between the catalyst and the C-5'-oxyanion of the basic alkoxy leaving group.

Elimination reactions of have been studied under various conditions. When X was moderately electron-withdrawing, Y = H, and base-solvent was NH-MeCN, the reaction proceeded by the E2 mechanism via an E1cb-like transition state. Concave downward curve was noted in the Hammett plots. When X = 4-, Y = Cl, , and the base-solvent was in 70 mol % MeCN(aq), the reaction proceeded by the E2 mechanism. The mechanism changed to a competing E2 and E1cb when X = 4- and Y = H, MeO, and to the E1cb when X = 2,4-(, and Y = . From these results, a plausible pathway of the change of the mechanism from E2 to the E1cb extreme is proposed.

Hydrolysis reactions of N-aryliminotriphenylphosphoranes (I) at varying pH have been investigated kinetically. The reactions produced aniline derivatives and triphenylphosphine oxide as the products. The reactions are first-order, and the Hammett ρ values are −0.29 and −0.63 at pH 3.0 and 8.0, respectively. The reaction rate increased linearly with acetate ion concentration at [AcO−] 8.0, the proton transfer from water to α-nitrogen of the iminophosphorane becomes the rate limiting step.

There has been significantprogress in both areas. However, the rate accelerationsreported to date for synthetic catalysts of RNA cleavage are,in general, far below those obtained for enzyme catalysts;and, there are a number of important unresolved questionsabout the mechanisms; the spon taneous and buffer-catalyzedcleavage reactions which have been set out with great clarityin a previous review.

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.

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.

Hydrolysis reactions of S-phenyl-S-vinyl-N-p-tosylsulfilimine (VSI) and its derivatives at various pH have been investigated kinetically. The hydrolysis reactions produced phenylvinylsulfoxide and p-toluene sulfonamide as the products. The reactions are first order and Hammett ρ values for pH 1.0, 6.0, and 11.0 are 0.82, 0.45, and 0.57, respectively. This reaction is not catalyzed by general base. The plot of k vs pH shows that there are three different regions of the rate constants ( kt) in the profile.; At pH 10, the rate constants are directly proportional to the concentrations of hydronium and hydroxide ion catalyzed reactions, respectively. The rate constant remains nearly the same at 2 10.0, the reaction proceeds by the addition of hydroxide ion to sulfur directly. In the range of pH 2.0-10.0, the addition of water to sulfur of sulfilimine appears to be the rate controlling step.

The new compounds catena -(μ-CrO 4 - O , O ′)[Ni(II)( L )]·5H 2 O and catena -(μ-MoO 4 - O , O ′)[Ni(II)(L)]·5H 2 O where L is 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, have been synthesized and structurally characterized by spectroscopy, magnetic susceptibility and X-ray crystallography. The nickel ions of the one-dimensional chain complexes are bridged by the tetraoxometalate ([CrO 4 ] 2− or [MoO 4 ] 2− ) unit. The magnetic properties of the chain complexes in the temperature range 5–300 K indicate that there are weak ferromagnetic intrachain interactions among the nickel ions. The electronic as well as infrared spectral properties of the title complexes are also reported and discussed.

Elimination reactions of N-(arylsulfonoxy)-N-alkylbenzylamines 1-5 with MeONa−MeOH have been studied kinetically. The elimination reactions are regiospecific, producing only corresponding benzylidenalkylamines. The rate equation for the reactions is k obs =k 0 +k 2 [MeONa], indicating that the reactions proceed by competing solvolytic- and base-promoted pathways. The relative rates of elimination for the k 2 and k 0 pathways are 1, 0.67, 0.53, 0.35, and 0.27 for R=Me, Et, i-Pr, s-Bu, and t-Bu and 1, 4.1, 5.1, and 8.7 for R=Et, i-Pr, s-Bu and t-Bu, respectively. For MeONa-promoted elimination from 1-5, Hammett p and k H /k D decrease but ρ 1g and |β 1g | increase with a bulkier alkyl substituent

Elimination reactions of (4'-ClC6H4)2CHCO2C6H3-2-X-4-NO2 promoted by R2NH-R2NH2+ in 70 mol% MeCN (aq.) have been studied kinetically. The reactions are second-order and exhibit Brönsted beta = 0.44-0.86 and /beta(lg)/ = 0.41-0.71. The Brönsted beta decreased with a poorer leaving group and /beta(lg)/ increased with a weaker base. The results are consistent with an E2 mechanism. When X=H, the reaction proceeded by the concurrent E2 and Elcb mechanism.