74104-89-5Relevant articles and documents
Kinetic study on alkaline hydrolysis of Y-substituted phenyl picolinates: Effects of modification of nonleaving group from benzoyl to picolinyl on reactivity and reaction mechanism
Kim, Myung-Joo,Kim, Min-Young,Um, Ik-Hwan
, p. 1138 - 1142 (2015/07/15)
Second-order rate constants (kOH-) for alkaline hydrolysis of Y-substituted phenyl picolinates (6a-6i) have been measured spectrophotometrically. A linear Bronsted-type plot is obtained with βlg = -0.34, which is typical for reactions reported previously to proceed through a stepwise mechanism with formation of an addition intermediate being the rate-determining step (RDS). However, σYo constants result in a much poorer Hammett correlation than σY- constants. Furthermore, the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρY = 0.82 and r = 0.72, indicating that a negative charge develops partially on the O atom of the leaving group in the RDS. Thus, the reactions have been concluded to proceed through a forced concerted mechanism with a highly unstable intermediate 7. Comparison of the current kinetic data with those reported previously for the corresponding reactions of Y-substituted phenyl benzoates has revealed that modification of the nonleaving group from benzoyl to picolinyl causes not only an increase in reactivity but also a change in the reaction mechanism (i.e., from a stepwise mechanism to a forced concerted pathway).
Kinetic and mechanistic studies on quinuclidinolysis of Y-substituted-phenyl picolinates: Effect of amine nature on reactivity and transition- state structure
Um, Ik-Hwan,Kim, Min-Young,Kang, Yeseul
, p. 1405 - 1410 (2015/07/15)
Second-order rate constants (kN) have been measured spectrophotometrically for reactions of Y-substitutedphenyl picolinates (7a-7i) with a series of quinuclidines in 80 mol% H2O/20 mol% DMSO at 25.0 ± 0.1 °C. The Bronsted-type plot f
Kinetic study on aminolysis of y-substituted-phenyl picolinates: Effect of h-bonding interaction on reactivity and transition-state structure
Kim, Min-Young,Kang, Tae-Ah,Yoon, Jung Hwan,Um, Ik-Hwan
, p. 2410 - 2414 (2014/11/08)
A kinetic study is reported on nucleophilic substitution reactions of Y-substituted-phenyl picolinates (7a-7h) with a series of cyclic secondary amines in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 °C. Comparison of the kinetic results with those reported previously for the corresponding reactions of Y-substituted-phenyl benzoates (1a-1f) reveals that 7a-7h are significantly more reactive than 1a-1f. The Bronsted-type plot for the aminolysis of 4-nitrophenyl picolinate (7a) is linear with βnuc = 0.78, which is typical for reactions proceeding through a stepwise mechanism with expulsion of the leaving group being the rate-determining step. The Bronsted-type plots for the piperidinolysis of 7a-7h and 1a-1f are also linear with βlg = -1.04 and -1.39, respectively, indicating that the more reactive 7a-7h are less selective than the less reactive 1a-1f to the leavinggroup basicity. One might suggest that the enhanced reactivity of 7a-7h is due to the inductive effect exerted by the electronegative N atom in the picolinyl moiety, while the decreased selectivity of the more reactive substrates is in accord with the reactivity-selectivity principle. However, the nature of intermediate (e.g., a stabilized cyclic intermediate through the intramolecular H-bonding interaction for the reactions of 7a-7h, which is structurally not possible for the reactions of 1a-1f) is also responsible for the enhanced reactivity with a decreased selectivity.
Aminolysis of aryl ester using tertiary amine as amino donor via c-o and c-n bond activations
Bao, Yong-Sheng,Zhaorigetu, Bao,Agula, Bao,Baiyin, Menghe,Jia, Meilin
, p. 803 - 808 (2014/04/03)
An aminolysis reaction between various aryl esters and inert tertiary amines by C-O and C-N bond activations has been developed for the selective synthesis of a broad scope of tertiary amides under neutral and mild conditions. The mechanism may undergo the two key steps of oxidative addition of acyl C-O bond in parent ester and C-N bond cleavage of tertiary amine via an iminium-type intermediate.
Metal ion catalysis in nucleophilic substitution reaction of 4-nitrophenyl picolinate with alkali metal ethoxides in anhydrous ethanol
Hong, Yeon-Ju,Kim, Song-I.,Um, Ik-Hwan
experimental part, p. 2483 - 2487 (2011/01/12)
Pseudo-first-order rate constants (kobsd) were measured spectrophotometrically for nucleophilic substitution reactions of 4-nitrophenyl picolinate (6) with alkali metal ethoxides (EtOM, M+ = K+, Na+ and Li+) in anhydrous ethanol at 25.0 ± 0.1 °C. The plot of kobsd vs. [EtOM] exhibits upward curvature regardless of the nature of M+ ions. However, the plot for the reaction of 6 with EtOK is linear with significantly decreased kobsd values when 18-crown-6-ether (18C6, a complexing agent for K+ ion) is added in the reaction medium. Dissection of kobsd into k EtO- and kEtOM (i.e., the second-order rate constant for the reaction with dissociated EtO- and ion-paired EtOM, respectively) has revealed that ion-paired EtOM is 3 ～ 17 times more reactive than dissociated EtO-. The reaction has been proposed to proceed through a 5-membered cyclic transition state, in which M+ ion increases the electrophilicity of the reaction site. Interestingly, Na+ ion exhibits the largest catalytic effect. The presence of a nitrogen atom in the pyridine moiety of 6 has been suggested to be responsible for the high Na + ion selectivity.
A simple method for synthesis of active esters of isonicotinic and picolinic acids
Christensen, Jorn B.
, p. 47 - 51 (2007/10/03)
A method for preparation of the p-nitrophenyl-, N-hydroxysuccinimidyl- and pentafluorophenyl esters of isonicotinic and picolinic acids from the corresponding acids is reported.
Decreased histamine release by luteinizing hormone-releasing hormone antagonists obtained upon translocation of the cationic amino acid from position 8 to position 7
Flouret,Mahan,Majewski
, p. 636 - 640 (2007/10/02)
We report analogues of N-Ac-D-Nal-D-Cpa-D-Pal-Ser-Lys(Pic)-D-Lys(Pic)-Leu- Ilys-Pro-D-Ala-NH2, the parent antagonist (PA), which is a potent antagonist of LHRH. To simplify future radioactive labeling we prepared N-Ac-D-Nal-D- Cpa-D-Pal-Ser-Lys
Divalent Metal Ion Catalysis in the Hydrolysis of Esters of Picolinic Acid. Metal Ion Promoted Hydroxide Ion and Water Catalyzed Reactions
Fife, Thomas H.,Przystas, Theodore J.
, p. 1041 - 1048 (2007/10/02)
Rate constants have been determined for hydrolysis of a series of phenolic and aliphatic esters of picolinic acid in H2O.Hydroxide ion, hydronium ion, and water catalyzed reactions were observed in hydrolysis of the phenolic esters.Catalysis by low concentrations of Ni2+ and Cu2+ occurs even though binding of the metal ions is weak (saturation effects were not observed).Both metal ion promoted water and OH- catalyzed reactions were observed with the esters having leaving groups with pKa values of 12.4 or less.Rate enhancements produced by 0.01 M Ni2+ and 0.001 M Cu2+ range from 10- to near 200-fold in the pH-independent water reactions and from 102- to over 105-fold in the OH- catalyzed reactions.Significant metal ion catalysis was not observed in the hydrolysis of 4-nitrophenyl isonicotinate or 8-(5-nitroquinolyl) isonicotinate; therefore, metal ion catalysis in the hydrolysis of the esters with the pyridine nitrogen ortho to the ester function must be associated with a chelation effect.The rate constants k0 and kOH for hydrolysis of the picolinate esters in the metal ion promoted water and OH- catalyzed reactions are little affected by the leaving group (β1g ca. 0) for leaving groups with pKa values ranging from 4.1 with 2,4-dinitrophenol to 12.4 with trifluoroethanol, and ratios of kOH/k0 are nearly constant.This indicates that there is little or no C-O bond breaking in the critical transition state, i.e., in both reactions the nucleophilic attack step is rate determining.When the leaving group is ethanol, then kOH is markedly less than in the case of the trifluoroethyl ester, and a metal ion promoted water reaction is not detected even at pH values as low as 4.Thus, a change in rate-determining step has occurred with the change in the leaving group.Likewise only metal ion promoted OH- catalysis is observed with ethyl 6-carboxypicolinate.Rate enhancements produced by saturating concentrations of Ni2+ and Cu2+ are in that the case 2.7*104- and 1.3*105-fold, respectively.Intramolecular general base catalysis does not occur in the metal ion promoted water reaction of 8-quinolyl picolinate or 8-(5-nitroquinolyl) picolinate.With the nitro substituted esters of picolinic acid a metal ion promoted formate and acetate ions are attacking the metal ion complexes as nucleophiles.
Synthesis and hypotensive activity of some analogs of the C-terminal hexapeptideamide of eledoisin
Von Dungen,Hoefke
, p. 589 - 591 (2007/10/02)
The C-terminal (6-11)-hexapeptideamide Ala-Phe-Ile-Gly-Leu-Met-NH2 of eledoisin was synthesized by the solid phase method according to Merrifield. The α-amino group of alanine was acylated with heterocyclic or aromatic residues. These new compo
