• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4387-4391
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• 2011

The kinetic studies on the pyridinolysis of diisopropyl thiophosphinic chloride have been carried out in acetonitrile at $55.0^{\circ}C$. The free energy correlations for substituent X variations in the X-pyridines are biphasic concave upwards with a break point at X = 3-Ph. A concerted SN2 mechanism is proposed with a change of the attacking direction of the X-pyridine from a frontside attack for the strongly basic pyridines to a backside attack for the weakly basic pyridines. The factors to determine the rates and thio effects on the rates for the pyridinolyses of thiophophinic chloride, chlorothiophosphate, phosphinic chloride, phosphonochloridothioate, and chlorophosphate systems are briefly reviewed on the basis of the magnitude of the positive charge of the reaction center P atom and steric effects of the two ligands.

• The Korean Journal of Food And Nutrition
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• v.5 no.1
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• pp.23-32
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• 1992

Kinetic studies of nucleophilic substitution reactions of dansyl, bansyl, dabsyl chlorides with pyridines have been investigated at $0^{\circ}C$ in a range of methanol-acetonitrile binary solvent mixtures. The order of magnitude for reactivity of substrates with pyridines in the same reaction condition is dabsyl chloride>dansyl chloride> bansyl chloride. The value of $\rho$n(-2.29~ -4.66) and $\beta$(0.537~0.901) associated with a change substituent in the nucleophile are large and indicate a relatively advanced bond formation in the transition state. Solvatochromic correlations were predicted the increase of bond formation transition state according to the increasing MeCN contents, showing the greater contribution of polarity polarizability ($\pi$*) than hydro-gen bond donar acidity($\alpha$). We conclude that the reactions of dansyl, bansyl, dabsyl chlorides with pyridines proceed via associative Sn2 type reaction mechanism.

• Bulletin of the Korean Chemical Society
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• v.34 no.8
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• pp.2340-2342
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• 2013

A convenient Rh-catalyzed C-H arylation of imidazo[1,2-a]pyridines with a variety of aryl halides or triflates has been reported. This process afforded a range of biaryl compounds in excellent yields and showed high activity and broad scope.

• Bulletin of the Korean Chemical Society
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• v.6 no.2
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• pp.99-102
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• 1985

Substituent effects of substrate and nucleophile for the reaction of substituted phenacyl tosylates with pyridines were determined conductometrically in acetonitrile. Activation parameters for these reactions were also calculated. The substituent effects in nucleophile were increased with electron-donating power of pyridines and Br${\o}$nsted linear relationship was shown. Rate constant was increased by both electron-donating and electron-attracting groups in the substrate. It seems that dissociative S$_{N}$2 ("loose" transition state) mechanism is operating in the case of electron-donating substituents while associative S$_{N}$2 ("tight" transition state) mechanism is operative in the case of electron-attracting substituents.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.1010-1013
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• 1997

Nucleophilic substitution reactions of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines were investigated in acetonitrile at 60 ℃ under respective pressures. The magnitudes of the Hammett reaction constants, ρX, ρY and ρZ indicate that a stronger nucleophile leads to a greater degree of bond formation of C-N and a better leaving group is accompanied by a less degree of bond breaking. The magnitude of correlation interaction term, ρij can be used to determine the structure of the transition state (TS) for the SN reaction. As the pressure is increased, the Hammett reaction constants, ρX and |ρY|, are decreased, but correlation interaction coefficient, ρXZ and |ρYZ|, are increased. The results indicate that the reaction of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines probably moves from a dissociative SN2 to early-type concerted SN2 mechanism by increasing pressure. This result shows that the correlation interaction term ρij can be useful tool to determine the structure of TS, and also the sign of the product ρXZ·ρYZ can be predict the movement of the TS.

• Bulletin of the Korean Chemical Society
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• v.18 no.11
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• pp.1179-1182
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• 1997

The rates for the reaction of (Z)-phenacyl (X)-benzenesulfonates with (Y)-pyridines in acetone were measured by an electrical conductivity method at 1-2000 bars and 45 ℃. The magnitudes of the Hammett reaction constants, ρX, ρY and ρZ, represent the degree of Nu-C bond formation and that of C-L bond breaking. The magnitude of correlation interaction term ρij can be used to determine the structure of the transition state (TS) for the SN reaction. As the pressure is increased, the Hammett reaction constants, ρX, |ρY| and ρZ are increased, but correlation interaction coefficient, |ρXZ| and ρYZ, are decreased. The results indicate that the reaction of (Z)-phenacyl (X)-benzenesulfonates with (Y)-pyridines probably moves from an associative SN2 to late-type SN2 mechanism by increasing pressure.

• Journal of the Korean Chemical Society
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• v.25 no.2
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• pp.110-118
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• 1981

Kinetics and mechanism for the reaction of substituted phenacyl bromides with substituted pyridines have been determined at 25, 35 and $45^{\circ}C$ in methanol and dimethylformamide by the conductivity method. The rate constants for the reaction of various pyridines with phenacyl bromide shown that electron-donating substituents in the pyridine increase the rate, while electron-attracting one decrease in both solvents. The effect of substituents in substrate, the rate being increased by electron-attracting substituents. This is as expected for nucleophilic attack of amines on the carbon atom. Isokinetic and $Br{\psi}nsted$ linear relationship were shown in the reaction of phenacyl bromide with pyridines in both solvent in which isokinetic temperature were obtained 614, $202^{\circ}K$ and ${\beta}$ values were 0.29, 0.36 in methanol and dimethylformamide respectively. In the case of the reaction of substituted phenacyl bromide with pyridines, isokinetic temperature decreases with increasing electron-attracting ability of the substituents in the phenacyl bromide, while the ${\beta}$ values were reverse. From the above results, it can be inferred that N…C bond formation decreases progressively from p-chloro- to p-methoxyphenacyl bromide and the bond formation predominates in DMF than methanol. The ${\rho}$ values of Hammett equation of the reaction of phenacyl bromide with substituted pyridines are negative in both solvent, but its value was larger negative in DMF than methanol and the ${\rho}$ value of that of substitutted substrates with pyridine was 0.3, the low value is ascribed to direct $S_N2$ attack of the nitrogen atom in pyridine ring at the methylene carbon.

• Archives of Pharmacal Research
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• v.13 no.4
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• pp.342-346
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• 1990

Several new pyridine, pyridinethione, pyrazole [3, 4-b]-pyridine, pyrido [1, 2-a]-1, 3-thiazine and pyrido[1, 2-a] pyridine thione derivatives have be synthesised via the reactions of 2-methyl-3-ethoxycarbonyl-4-phenyl-5-cyano-1, 4, 5, 6-tetrahydro-pyridine-6-one 2 with different rfeagents. The structures of the newly synthesised derivatives were established on the basis of elemental analyses and spectral data studies.

• Archives of Pharmacal Research
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• v.22 no.4
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• pp.391-397
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• 1999

The quaternary ammonium cephalosporin derivatives were prepared with various pyridines substituted at the 3 or/and 4 position. Their in vitro antibacterial activities were determined and substituent effect on pyridine nucleus was studied. Preparation of substituted pyridines are also described.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1719-1722
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• 2010