- Hydrodefluorination of functionalized fluoroaromatics with triethylphosphine: A theoretical and experimental study
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Recently we reported the metal free hydrodefluorination of selected fluoroaromatics using triethylphosphine as the sole defluorinating agent. That prompted us to evaluate the mechanistic proposal and in the light of these results, along with new experimental evidence, we have now modified the initial proposal. The new mechanism avoids the highly energetic β-elimination step of roughly 71 kcal mol-1 for hexafluorobenzene and pentafluoropyridine at 393.15 K, invoking the participation of water. The use of D2O confirmed the role of water as the hydrogen source, yielding the corresponding deutero-defluorinated products; DFT calculations agree with this new proposed mechanism. We also report herein the use of this one-pot hydrodefluorination method applied to a broader number of fluoroaromatic derivatives; some of them allowed the collection of key mechanistic evidence.
- Facundo, Aldo A.,Arévalo, Alma,Fundora-Galano, Gabriela,Flores-álamo, Marcos,Orgaz, Emilio,García, Juventino J.
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p. 6897 - 6908
(2019/05/17)
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- Fragmentation of radical anions of polyfluorinated benzoates
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A comprehensive study of the symmetry forbidden fragmentation of short-lived radical anions (RAs) has been undertaken for the complete set of polyfluorinated benzoates (C6FnH5-nCO22, n = 1-5). The decay rate constants (kc) of RAs have been determined in aqueous alkaline solution (pH 13.4) by electron photoinjection (EPI) from mercury electrodes and were found to increase dramatically from ≤3 × 103 s-1 (3-F - C6H4CO2-) to (1.2 ± 0.8) × 109 s-1 (C6F5CO2-). The regioselectivity of C-F bond cleavage in the RA fragmentation has been revealed by structure assignment of reduction products of the polyfluorinated benzoic acids by Na, K, and Zn in liquid NH3, as well as by Zn in aqueous NH3 and aqueous alkaline solutions. The kc values depend on the position of the cleaved fluorine to the CO2- group generally in the order para > ortho > meta, and to sharply increase if adjacent fluorine atoms are present. The observed trends reveal that the kinetics of the RA fragmentation reaction is not controlled by the reaction thermodynamics. Semiempirical UHF/INDO calculations, the validity of which has been confirmed by ab initio ROHF/6-31+G calculations, were done to rationalize the observed trends. The reaction transition state (TS) was considered to arise from the RA's and 2*states crossing avoided due to out-of-plane deviation of the cleaving C-F bond. The satisfactory linear correlation (R = 0.96) between the model reaction energy barrier Ea and log kc has been achieved with modeling the local solvation of the CO2- group by its protonation.
- Konovalov, Valery V.,Laev, Sergey S.,Beregovaya, Irina V.,Shchegoleva, Lyudmila N.,Shteingarts, Vitalij D.,Tsvetkov, Yuri D.,Bilkis, Itzhak
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p. 352 - 361
(2007/10/03)
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- Antimycotically active substituted 2-aminothiazoles
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Antimicotically active 2-aminothiazoles have been found having the formula STR1 in which R1 represents hydrogen or alkyl and R2 represents optionally substituted cyclohexyl or phenyl which is substituted by halogen, alkyl, halogenoalkyl, halogenoalkoxy, dioxyhalogenoalkyl or halogenoalkylthio, and their physiologically tolerable acid addition salts, with the exception of the compounds 4-(4-chlorophenyl)-2-[2-(1,4,5,6-tetrahydropyrimidinyl)-amino]thiazole and 4-(2,4-dichlorophenyl)-2-[2-(1,4,5,6-tetrahydropyrimidinyl)-amino]-thiazole and 4-(4-chloro-2-methylphenyl)-2-[2-(1,4,5,6-tetrahydropyrimidinyl)-amino]-thiazole and with the exception of the physiologically tolerable acid addition salts of these compounds have been found.
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- Fluorine-containing acetophenones optionally halogenated on the CH3 -group and their precurser fluorine-containing benzonitriles
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Fluorine-containing acetophenones, optionally halogenated on the CH3 group, of the formula STR1 in which X represents hydrogen, chlorine or bromine and the radicals R1 to R5 have the following meaning, a) R1 and R4 denote fluorine, R2 and R5 denote chlorine and R3 denotes CF3, or b) R1, R3 and R4 denote fluorine and R2 and R5 denote hydrogen, or c) R1, R4 and R5 denote hydrogen, R2 denotes chlorine and R3 denotes CF3, or d) R1, R4 and R5 denote hydrogen, R2 denotes chlorine and R3 denotes OCF3, or e) R1, R4 and R5 denote hydrogen and R2 and R3 denote CF3, or f) R1 denotes chlorine, R2 denotes CF3 and R3, R4 and R5 denote hydrogen, or g) R1 denotes chlorine, R2, R3 and R4 denote hydrogen and R5 denotes CF3, or h) R1 denotes chlorine, R2, R4 and R5 denote hydrogen and R3 denotes CF3 and a process for their preparation from the corresponding fluorinated benzonitriles or benzyl halides by reaction with an organomagnesium compound capable of introducing methyl groups and subsequent hydrolysis, if appropriate followed by a chlorination or bromination.
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- Synthesis, Antibacterial Activities, and Pharmacological Properties of Enantiomers of Temafloxacin Hydrochloride
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Temafloxacin hydrochloride is a potent member of the 4-pyridone-3-carboxylic acid class of antibacterial agents and is currently under clinical development as a broad-spectrum antimicrobial agent.It is a racemate having a chiral center at the C3 of the 7-piperazin-1-yl group.The two enantiomers were synthesized and tested for their antibacterial activities.Although no difference in in vitro antibacterial activities was observed, a minor difference in in vivo antibacterial activities was observed.However, they both exhibited similar pharmacological profiles.
- Chu, Daniel T. W.,Nordeen, Carl W.,Hardy, Dwight J.,Swanson, Robert N.,Giardina, William J.,et al.
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p. 168 - 174
(2007/10/02)
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