- Electrocatalytic dechlorination of chloropicolinic acid mixtures by using palladium-modified metal cathodes in aqueous solutions
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In China, chloropicolinic acid (ClPA) mixtures comprising 3,5,6-trichloropicolinic acid, 3,6-dichloropicolinic acid (3,6-D), 3-ClPA, and 6-ClPA are discharged as organic wastes at a rate of approximately 300 tons per year. In this work, we developed an aqueous phase electrocatalytic hydrogenation (ECH) system based on Pd catalyst to dechlorinate the ClPA mixtures into picolinic acid (PA) at room temperature. Firstly, we evaluated the influence of cathode support and Pd loading on the catalytic performance of cathodes, as well as the effects of operating parameters on the intermediate product selectivity and dechlorination efficiency of the ECH process with 3,6-D as the target compound. Secondly, we analyzed the ECH dechlorination mechanism of 3,6-D with regard to the surface condition of cathode and catholyte pH, and the rate-limiting step of the dechlorination process was also discussed. Finally, we assessed the practicability of the ECH system to dechlorinate the ClPA mixtures into PA by using a plate-and-frame cell. Results demonstrated that Pd/Ni foam cathodes with Pd loading of 2.25-3.6 mg cm-2 exhibited the optimum ECH dechlorination performance, and the basic aqueous solution and high 3,6-D concentration favored the ECH process. The ClPA mixtures with 47 g L-1 concentration (the total concentration of ClPAs was approximately 250 mM) can be selectively dechlorinated into PA with 99% yield, 76.3% current efficiency, and 2.47 kW h kg-1 PA specific electric energy consumption at a current density of 208 A m-2 in a 1.25 M NaOH aqueous solution.
- Ma, Hongxing,Xu, Yinghua,Ding, Xufen,Liu, Qi,Ma, Chun-An
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- Synthesis method of 3-cloro-5-bromo-2-picolinic acid
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The invention discloses a synthesis method of 3-cloro-5-bromo-2-picolinic acid, and belongs to the field of chemosynthesis. According to the method, 3-aminopyridine is used as raw materials; concentrated hydrochloric acid and hydrogen peroxide are added for preparing a diazonium salt solution; CuCl, dichloromethane and concentrated hydrochloric acid are added into a three-mouth flask; the diazonium salt solution is dropwise added into the three-mouth flask; the pH value is regulated; extraction, separation and rotary evaporation are carried out to obtain 2, 3-dichloropyridine; absolute ethyl alcohol is used for dissolution; a hydrazine hydrate solution is dropwise added into the flask; under the nitrogen gas protection, backflow is carried out; 3-cloro-2-cyanopyridine can be obtained; then, through specific conditions, the 3-cloro-2-cyanopyridine is used for producing 3-chloropyridine-2-picolinic acid; then, N-bromo-succinimide is added for performing a bromination reaction to finally obtain the 3-cloro-5-bromo-2-picolinic acid.
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Paragraph 0007
(2017/01/23)
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- Directed lithiation of unprotected pyridinecarboxylic acids: Syntheses of halo derivatives
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Deprotonation of all isomeric lithium pyridinecarboxylates and subsequent trapping with hexachloroethane or iodine afforded straightforward access to chloro- and iodopyridinecarboxylic acids, respectively. Starting from lithium 5-bromonicotinate, the introduction of an iodine atom at C4 and further halogen migration allowed the potential of this method to be extended to the synthesis of more elaborate derivatives.
- Lazaar, Jalal,Rebstock, Anne-Sophie,Mongin, Florence,Godard, Alain,Trécourt, Fran?ois,Marsais, Francis,Quéguiner, Guy
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p. 6723 - 6728
(2007/10/03)
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- Synthesis, rotamer orientation, and calcium channel modulation activities of alkyl and 2-phenethyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3- or 6-substituted-2-pyridyl)-5-pyridinecarboxylates
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A group of racemic alkyl and 2-phenethyl 1,4-dihydro-2,6-dimethyl-3- nitro-4-(3- or 6-substituted-2-pyridyl)-5-pyridinecarboxylates (13a-q) was prepared using a modified Hantzsch reaction that involved the condensation of a 3- or 6-substituted-2-pyridinecarboxaldehyde (7a-j) with an alkyl or 2- phenethyl 3-aminocrotonate (11a-d) and nitroacetone (12). Nuclear Overhauser (NOE) studies indicated there is a significant rotamer fraction in solution where the pyridyl nitrogen is oriented above the 1,4-dihydropyridine ring, irrespective of whether a substituent is located at the 3- or 6-position. A potential H-bonding interaction between the pyridyl nitrogen free electron pair and the suitably positioned 1,4-dihydropyridine NH moiety may stablize this rotamer orientation. In vitro calcium channel antagonist and agonist activities were determined using guinea pig ileum longitudinal smooth muscle (GPILSM) and guinea pig left atrium (GPLA) assays, respectively. Compounds having an i-Pr ester substituent acted as dual cardioselective calcium channel agonists (GPLA)/smooth muscle-selective calcium channel antagonists (GPILSM), except for the C-4 3-nitro-2-pyridyl compound which exhibited an antagonist effect on both GPLA and GPILSM. In contrast, the compounds with a phenethyl ester group, which exhibited antagonist activity (IC50 = 10-5- 10-7 M range) on GPILSM, were devoid of cardiac agonist activity on GPLA. Structure-activity relationships showing the effect of a substituent (Me, CF3, C1, NO2, Ph) at the 3- or 6-position of a C-4 2-pyridyl moiety and a variety of ester substituents (Me, Et, i-Pr, PhCH2CH2-) upon calcium channel modulation are described. Compounds possessing a 3- or 6-substituted- 2-pyridyl moiety, in conjuction with an i-Pr ester substituent, are novel 1,4-dihydropyridine calcium channel modulators that offer a new drug design approach directed to the treatment of congestive heart failure and may also be useful as probes to study the structure-function relationships of calcium channels.
- Iqbal, Nadeem,Akula, Murthy R.,Vo, Dean,Matowe, Wandikayi C.,McEwen, Carol-Anne,Wolowyk, Michael W.,Knaus, Edward E.
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p. 1827 - 1837
(2007/10/03)
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- Application of organolithium compounds in organic synthesis. Part 19. Synthetic strategies based on aromatic metallation. A concise regiospecific synthesis of 3-halogenated picolinic and isonicotinic acids
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The synthesis of the halogenated picolin- and isonicotinalides (3) and (4) via metallation (n-BuLi) of the anilides (1) and (2) and then the reaction of the generated bis-lithiated anilides with halogenating agents (CCl3-CCl3, CH2Br-CH2Br, I2) followed by subsequent acidic hydrolysis of (3) and (4), as a way of regiospecific transformation of picoline and isonicotine acids into their C3-halogenated derivatives, is described.
- Epsztajn,Plotka,Grabowska
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p. 1075 - 1086
(2007/10/03)
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- Phytotoxic 2-alkyl-5-(heterocyclic)-pyrrole-3,4-dicarboxylates
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Phytotoxic 2-methyl-5-(heterocyclic)-pyrrole-3,4-dicarboxylates.
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