- Design, synthesis, and biological evaluation of 1,2,4-oxadiazole-containing pyrazolo[3,4-b]pyridinones as a new series of AMPKɑ1β1γ1 activators
-
Adenosine monophosphate-activated protein kinase (AMPK) plays a key role in maintaining whole-body homeostasis and has been regarded as a therapeutic target for the treatment of diabetic nephropathy (DN). Herein, a series of 1,2,4-oxadiazole-containing py
- Xiao, Zhihong,Peng, Yajun,Zheng, Bifeng,Chang, Qi,Guo, Yating,Chen, Zhuo,Li, Qianbin,Hu, Gaoyun
-
-
- KCNT1 INHIBITORS AND METHODS OF USE
-
The present invention is directed to, in part, compounds and compositions useful for preventing and/or treating a neurological disease or disorder, a disease or condition relating to excessive neuronal excitability, and/or a gain-of-function mutation in a gene (e.g., KCNT1). Methods of treating a neurological disease or disorder, a disease or condition relating to excessive neuronal excitability, and/or a gain-of-function mutation in a gene such as KCNT1 are also provided herein.
- -
-
Paragraph 000269; 000355; 000357; 000448
(2020/11/23)
-
- Efficient Synthesis of Functionalized Indene Derivatives via Rh(III)-Catalyzed Cascade Reaction between Oxadiazoles and Allylic Alcohols
-
A highly efficient rhodium(III)-catalyzed synthesis of novel functionalized indene derivatives has been achieved via C?H activation/intramolecular aldol condensation. This cascade reaction is an atom economical protocol which could be further applied to build more complex compounds. (Figure presented.).
- Zhang, Jing,Sun, Jun-Shu,Xia, Ying-Qi,Dong, Lin
-
supporting information
p. 2037 - 2041
(2019/03/28)
-
- Novel 5-(quinuclidin-3-ylmethyl)-1,2,4-oxadiazoles to investigate the activation of the α7 nicotinic acetylcholine receptor subtype: Synthesis and electrophysiological evaluation
-
α7 nicotinic acetylcholine receptors (nAChRs) are relevant therapeutic targets for a variety of disorders including neurodegeneration, cognitive impairment, and inflammation. Although traditionally identified as an ionotropic receptor, the α7 subtype showed metabotropic-like functions, mainly linked to the modulation of immune responses. In the present work, we investigated the structure-activity relationships in a set of novel α7 ligands incorporating the 5-(quinuclidin-3-ylmethyl)-1,2,4-oxadiazole scaffold, i.e. derivatives 21a-34a and 21b-34b, aiming to identify the structural requirements able to preferentially trigger one of the two activation modes of this receptor subtype. The new compounds were characterized as partial and silent α7 nAChR agonists in electrophysiological assays, which allowed to assess the contribution of the different groups towards the final pharmacological profile. Overall, modifications of the selected structural backbone mainly afforded partial agonists, among them tertiary bases 27a-33a, whereas additional hydrogen-bond acceptor groups in permanently charged ligands, such as 29b and 31b, favored a silent desensitizing profile at the α7 nAChR.
- Quadri, Marta,Silnovi?, Almin,Matera, Carlo,Horenstein, Nicole A.,Stokes, Clare,De Amici, Marco,Papke, Roger L.,Dallanoce, Clelia
-
p. 207 - 228
(2018/10/23)
-
- Pharmacophore requirements for HIV-1 reverse transcriptase inhibitors that selectively “Freeze” the pre-translocated complex during the polymerization catalytic cycle
-
Reverse transcriptase (RT) is responsible for replicating the HIV-1 genome and is a validated therapeutic target for the treatment of HIV infections. During each cycle of the RT-catalyzed DNA polymerization process, inorganic pyrophosphate is released as the by-product of nucleotide incorporation. Small molecules were identified that act as bioisosteres of pyrophosphate and can selectively freeze the catalytic cycle of HIV-1 RT at the pre-translocated stage of the DNA- or RNA-template-primer-enzyme complex.
- Lacbay, Cyrus M.,Menni, Michael,Bernatchez, Jean A.,G?tte, Matthias,Tsantrizos, Youla S.
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p. 1713 - 1726
(2018/02/27)
-
- Synthesis and antibacterial evaluation of 3,5-Diaryl-1,2,4-oxadiazole derivatives
-
This manuscript reports the synthesis of twenty 3,5-diaryl-1,2,4-oxadiazole derivatives, nine of which are novel compounds. The amidoxime reaction with acyl chlorides obtained from substituted benzoic acids was used. All compounds were tested against five standard (American Type Culture Collection (ATCC)) bacteria: Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Proteus mirabilis and Staphylococcus aureus. Screening assays were carried out using agar-diffusion technique, in which 100 μM heterocyclic compounds solutions (20percent dimethylsulfoxide/water) were employed. The minimum inhibitory concentrations (MIC) of the active compounds were determined by serial dilutions at decreasing concentrations in microtiter plates. The nitrated derivatives gave the best test results, where MIC = 60 μM (E. coli) was the lowest value found for an ortho-nitrated derivative. The activity of these compounds possibly involves a mechanism via free radicals. S. aureus and P. aeruginosa were resistant to all compounds.
- Cunha, Felipe S.,Nogueira, Joseli M. R.,De Aguiar, Alcino P.
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p. 2405 - 2416
(2018/10/20)
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- Indazole-oxadiazole derivative, medicinal composition containing derivative, and application of derivative in tumor prevention
-
The invention discloses an indazole-oxadiazole derivative with the structure represented by general formula a shown in the description, or a pharmaceutically acceptable salt or solvate thereof. In the formula, X is O or N, Y is N, Z is N or O, and all groups are as defined in the description. The invention also discloses a medicinal composition adopting the derivative as an active component, and a use of the derivative. Compounds synthesized in the invention have an HIF-1 inhibition effect, and most of the compounds have a substantial HIF-1 inhibition effect, have strong in-vivo and in-vitro anti-HIF-1 effect on human colorectal carcinoma cell strains (HCT116) and other tumor cell strains, and can be used for treating tumor diseases.
- -
-
Paragraph 0099; 0100; 0131; 0132
(2017/07/25)
-
- Nitrobenzofurazan derivatives of N′-hydroxyamidines as potent inhibitors of indoleamine-2,3-dioxygenase 1
-
Tryptophan metabolism through the kynurenine pathway is considered as a crucial mechanism in immune tolerance. Indoleamine 2,3-dioxygenase 1 (IDO1) plays a key role in tryptophan catabolism in the immune system and it is also considered as an important therapeutic target for the treatment of cancer and other diseases that are linked with kynurenine pathway. In this study, a series of nitrobenzofurazan derivatives of N′-hydroxybenzimidamides (1) and N′-hydroxy-2-phenylacetimidamides (2) were synthesized and their inhibitory activities against human IDO1 enzyme were tested using in-vitro and cellular enzyme activity assay. The optimization leads to the identification of potent compounds, 1d, 2i and 2k (IC50 = 39-80 nM), which are either competitive or uncompetitive inhibitors of IDO1 enzyme. These compounds also showed IDO1 inhibition potencies in the nanomolar range (IC50 = 50-71 nM) in MDA-MB-231 cells with no/negligible amount of cytotoxicity. The stronger selectivity of the potent compounds for IDO1 enzyme over tryptophan 2,3-dioxygenase (TDO) enzyme (312-1593-fold) also makes them very attractive for further immunotherapeutic applications.
- Paul, Saurav,Roy, Ashalata,Deka, Suman Jyoti,Panda, Subhankar,Trivedi, Vishal,Manna, Debasis
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p. 364 - 375
(2016/06/13)
-
- PIPERIDINYLPYRAZOLOPYRIMIDINONES AND THEIR USE
-
The present application relates to novel substituted piperidinylpyrazolopyrimidinones, to processes for their preparation, the compounds for use alone or in combinations in a method for the treatment and/or prophylaxis of diseases, in particular for the treatment and/or prophylaxis of acute and recurrent bleeding in patients with or without underlying hereditary or acquired hemostatic disorders, wherein the bleeding is associated with a disease or medical intervention selected from the group consisting of heavy menstrual bleeding, postpartum hemorrhage, hemorrhagic shock, hemorrhagic cystitis, gastrointestinal hemorrhage, trauma, surgery, transplantation, stroke, liver diseases, hereditary angioedema, nosebleed, and synovitis and cartilage damage following hemarthrosis.
- -
-
Page/Page column 212
(2016/06/01)
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- Iron(III) Chloride/l-Proline as an Efficient Catalyst for the Synthesis of 3-Substituted 1,2,4-Oxadiazoles from Amidoximes and Triethyl Orthoformate
-
A general, facile, and efficient method is presented for the synthesis of 3-substituted 1,2,4-oxadiazoles from amidoximes and triethyl orthoformate. The procedure employs an iron(III) chloride/l-proline catalytic system and the 3-substituted 1,2,4-oxadiaz
- Kaboudin, Babak,Kazemi, Foad,Pirouz, Maryam,Khoshkhoo, Aysan Baharian,Kato, Jun-Ya,Yokomatsu, Tsutomu
-
p. 3597 - 3602
(2016/10/18)
-
- Novel potent HIF-1 inhibitors for the prevention of tumor metastasis: discovery and optimization of 3-aryl-5-indazole-1,2,4-oxadiazole derivatives
-
Hypoxia inducible factor-1 (HIF-1) is the key transcription factor of cellular response to hypoxia and plays a critical role in tumor metastasis. We describe here the discovery and a structure-activity relationship study of a series of 3-aryl-5-indazole-1,2,4-oxadiazole derivatives as novel HIF-1 inhibitors. The two most promising compounds 4g and 4h inhibit HIF-1 transcription with IC50 values of 0.62 and 0.55 μM in vitro, respectively, and they exhibit more efficient HIF-1 inhibition in xenograft tumors than YC-1, a potential anticancer drug targeting HIF-1. In addition, they also remarkably prevent the hypoxia-driven migration of SKOV3 cells in vitro and tumor metastasis in vivo. Further investigation of the mechanism revealed that the two inhibitors could decrease HIF-1α and VEGF expression. These results suggest that our newly synthesized HIF-1 inhibitors 4g and 4h are potential therapeutic agents with which to treat tumor metastasis.
- Sheng, Rong,Li, Shan,Lin, Guanyu,Shangguan, Shihao,Gu, Yongchuan,Qiu, Ni,Cao, Ji,He, Qiaojun,Yang, Bo,Hu, Yongzhou
-
p. 81817 - 81830
(2015/10/12)
-
- COMPOUNDS HAVING AN ETHR INHIBITING ACTIVITY - USE OF SAID COMPOUNDS AS DRUGS - PHARMACEUTICAL COMPOSITION AND PRODUCT CONTAINING SAID COMPOUNDS
-
The present invention relates to compounds of Formula (I), wherein R1 is chosen among the following radicals : (II); (III); (IV), (V), (VI) (VII) and n= 1 or 2 and m=1 or 2 with the proviso that m=2 when R1 is (VIII). The present invention also relates to the use thereof as drugs, more particularly in the treatment of mycobacterial infections and more particularly in the treatment of tuberculosis.
- -
-
Page/Page column 10
(2013/05/21)
-
- Ethionamide boosters. 2. Combining bioisosteric replacement and structure-based drug design to solve pharmacokinetic issues in a series of potent 1,2,4-oxadiazole EthR inhibitors
-
Mycobacterial transcriptional repressor EthR controls the expression of EthA, the bacterial monooxygenase activating ethionamide, and is thus largely responsible for the low sensitivity of the human pathogen Mycobacterium tuberculosis to this antibiotic.
- Flipo, Marion,Desroses, Matthieu,Lecat-Guillet, Nathalie,Villemagne, Baptiste,Blondiaux, Nicolas,Leroux, Florence,Piveteau, Catherine,Mathys, Vanessa,Flament, Marie-Pierre,Siepmann, Juergen,Villeret, Vincent,Wohlk?nig, Alexandre,Wintjens, René,Soror, Sameh H.,Christophe, Thierry,Jeon, Hee Kyoung,Locht, Camille,Brodin, Priscille,Déprez, Benoit,Baulard, Alain R.,Willand, Nicolas
-
experimental part
p. 68 - 83
(2012/03/10)
-
- Organic reactions in water: An efficient method for the synthesis of 1,2,4-oxadiazoles in water
-
A simple and efficient process has been developed for the synthesis of 1,2,4-oxadiazoles in good yields through the reaction of amidoximes with anhydrides under catalyst-free conditions in water.
- Kaboudin, Babak,Malekzadeh, Leila
-
supporting information; experimental part
p. 6424 - 6426
(2011/12/22)
-
- An efficient one-pot synthesis of 3-aryl-1,2,4-oxadiazol-5-amines under solvent-free conditions
-
The in situ prepared amidoximes from the reaction between nitriles and hydroxylamine are condensed with carbodiimides in the presence of molecular sieves under solvent-free conditions to produce the title compounds in excellent yields.
- Adib, Mehdi,Bagherzadeh, Sharareh,Mahdavi, Mohammad,Bijanzadeh, Hamid R.
-
experimental part
p. 50 - 51
(2010/04/25)
-
- Hit-to-lead optimization of disubstituted oxadiazoles and tetrazoles as mGluR5 NAMs
-
Here we report the discovery and early SAR of a series of mGluR5 negative allosteric modulators (NAMs). Starting from a moderately active HTS hit we synthesized 3,5-disubstituted-oxadiazoles and tetrazoles as mGluR5 NAMs. Based on the analysis of ligand e
- Wágner, Gábor,Wéber, Csaba,Nyéki, Olga,Nógrádi, Katalin,Bielik, Attila,Molnár, László,Bobok, Amrita,Horváth, Attila,Kiss, Béla,Kolok, Sándor,Nagy, József,Kurkó, Dalma,Gál, Krisztina,Greiner, István,Szombathelyi, Zsolt,Keser, Gy?rgy M.,Domány, Gy?rgy
-
scheme or table
p. 3737 - 3741
(2010/08/20)
-
- Synthesis, mechanism of formation, and molecular orbital calculations of arylamidoximes
-
A simple and easy synthesis of ten arylamidoximes from arylnitriles and hydroxylamine is described. The formation of the arylamides has been observed to a much lesser extent in the present work. A new mechanism for the formation of arylamidoximes, as well
- Srivastava, Rajendra M.,Pereira, Maria C.,Faustino, Wagner W. M.,Coutinho, Kaline,Dos Anjos, Janaina V.,De Melo, Sebastiao J.
-
experimental part
p. 1319 - 1324
(2010/05/18)
-
- Synthesis, characterization, and antimicrobial activities of clubbed [1,2,4]-oxadiazoles with fluorobenzimidazoles
-
(Chemical Equation Presented) In this study, a novel series of substituted 4,6-difluoro-2-{2-[3-(substituted-phenyl)-[1,2,4]-oxadiazol-5-yl]-ethyl} -1H-benzo[d]imidazole derivatives were synthesized by condensation of 2,4-difluoro-6-nitrophenyl amine with 3-(substitutedphenyl-[1,2,4]-oxadiazol- 5yl) propionic acid by using 2,4,6-trichlorobenzoyl chloride in the presence of triethyl amine base. The compounds were evaluated for their preliminary in vitro antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and Salmonella typhosa. The antibacterial data of the tested compounds indicated that most of the synthesized compounds showed moderate activity with reference standard Gentamycin.
- Jadhav, Ganesh R.,Shaikh, Mohammad U.,Kale, Rajesh P.,Ghawalkar, Anand R.,Gill, Charansingh H.
-
experimental part
p. 980 - 987
(2009/12/05)
-
- Polycyclic systems containing 1,2,4-oxadiazole ring 2*. 4-(1,2,4-Oxadiazol-5-YL)pyrrolidin-2-ones: Synthesis and prediction of biological activity
-
A one-pot condensation of 5-oxopyrrolidine-3-carboxylic acids, carbonyldiimidazole, and benzamidoximes leads to the formation of the novel 4-(1,2,4-oxadiazol-5-yl)pyrrolidin-2-one bicyclic systems, the structures of which have been confirmed by IR and su
- Kharchenko,Detistov,Orlov
-
p. 600 - 605
(2013/07/11)
-
- Discovery and optimization of a novel series of N-arylamide oxadiazoles as potent, highly selective and orally bioavailable cannabinoid receptor 2 (CB 2) agonists
-
The CB2 receptor is an attractive therapeutic target for analgesic and anti-inflammatory agents. Herein we describe the discovery of a novel class of oxadiazole derivatives from which potent and selective CB 2 agonist leads were developed. Initial hit 7 was identified from a cannabinoid target-biased library generated by virtual screening of sample collections using a pharmacophore model in combination with a series of physicochemical filters. 7 was demonstrated to be a selective CB2 agonist (CB2 EC50 = 93 nM, Emax = 98%, CB 1 EC50 > 10 μM). However, this compound exhibited poor solubility and relatively high clearance in rat, resulting in low oral bioavailability. In this paper, we report detailed SAR studies on 7 en route toward improving potency, physicochemical properties, and solubility. This effort resulted in identification of 63 that is a potent and selective agonist at CB2 (EC50 = 2 nM, Emax = 110%) with excellent pharmacokinetic properties.
- Cheng, Yuan,Albrecht, Brian K.,Brown, James,Buchanan, John L.,Buckner, William H.,DiMauro, Erin F.,Emkey, Renee,Fremeau Jr., Robert T.,Harmange, Jean-Christophe,Hoffman, Beth J.,Huang, Liyue,Huang, Ming,Lee, Josie Han,Lin, Fen-Fen,Martin, Matthew W.,Nguyen, Hung Q.,Patel, Vinod F.,Tomlinson, Susan A.,White, Ryan D.,Xia, Xiaoyang,Hitchcock, Stephen A.
-
experimental part
p. 5019 - 5034
(2009/07/19)
-
- Substituted piperazines as metabotropic glutamate receptor antagonists
-
The invention relates to compounds of formula I or pharmaceutically acceptable salts or solvates thereof: where Ar1, Ar2, Hy, L, R1, m and n are as defined in the description. The invention also includes pharmaceutical compositions and uses thereof, processes for making the compounds, as well as methods for the medical treatment of mGluR5-mediated disorders.
- -
-
Page/Page column 21
(2008/06/13)
-
- Novel 1,3-dipropyl-8-(1-heteroarylmethyl-1H-pyrazol-4-yl)-xanthine derivatives as high affinity and selective A2B adenosine receptor antagonists
-
A series of new 1,3-dipropyl-8-(1-heteroarylmethyl-1H-pyrazol-4-yl)- xanthine derivatives as A2B-AdoR antagonists have been synthesized and evaluated for their binding affinities for the A2B, A 1, A2A, and A3-AdoRs. 8-(1-((3-phenyl-1,2,4- oxadiazol-5-yl)methyl)-1H-pyrazol-4-yl)-1,3-dipropyl-1H-purine-2,6(3H,7H)-dione (4) displayed high affinity (Ki = 1 nM) and selectivity for the A2B-AdoR versus A1, A2A, and A 3-AdoRs (A1/A2B, A2A/A2B, and A3/A2B selectivity ratios of 370, 1100, and 480, respectively). The synthesis and SAR of this novel class of compounds are presented herein.
- Elzein, Elfatih,Kalla, Rao,Li, Xiaofen,Perry, Thao,Parkhill, Eric,Palle, Venkata,Varkhedkar, Vaibahv,Gimbel, Art,Zeng, Dewan,Lustig, David,Leung, Kwan,Zablocki, Jeff
-
p. 302 - 306
(2007/10/03)
-
- A novel, one-pot, three-component synthesis of 1,2,4-oxadiazoles under microwave irradiation and solvent-free conditions
-
A novel synthesis of 3,5-disubstituted 1,2,4-oxadiazoles is described from a one-pot, three-component reaction between nitriles, hydroxylamine, and Meldrum's acids under microwave irradiation and solvent-free conditions in good to excellent yields. Georg
- Adib, Mehdi,Mahdavi, Mohammad,Mahmoodi, Niusha,Pirelahi, Hooshang,Bijanzadeh, Hamid Reza
-
p. 1765 - 1767
(2008/02/04)
-
- HETEROCYCLIC COMPOUNDS USEFUL AS DPP- IV INHIBITORS
-
The invention relates to compounds of formula Z-C(R1R2)-C(R3NH2)-C(R4R5)-A (I) wherein Z, R1-R5 and A have the meaning as cited in the description and the claims as examplified by the compound (II) said compounds are useful as DPP-IV inhibitors. The invention also relates to the preparation of such compounds as well as the production and use thereof as medicament.
- -
-
Page/Page column 27
(2010/10/19)
-
- NOVEL ALKYNYL DERIVATIVES AS MODULATORS OF METABOTROPIC GLUTAMATE RECEPTORS
-
The present invention relates to novel compounds of formula (I) wherein W, n, X and W’ are defined in the description; invention compounds are modulators of metabotropic glutamate receptors - subtype 5 (“mGluR5”) which are useful for the treatment of central nervous system disorders as well as other disorders modulated by mGluR5 receptors.
- -
-
Page/Page column 113
(2008/06/13)
-
- Antikinetoplastid activity of 3-aryl-5-thiocyanatomethyl-1,2,4-oxadiazoles
-
A series of 5-thiocyanatomethyl- and 5-alkyl-3-aryl-1,2,4-oxadiazoles were synthesized and evaluated for their activity against kinetoplastid parasites. Formation of the oxadiazole ring was accomplished through the reaction of benzamidoximes with acyl chlorides, while the thiocyanate group was inserted by reacting the appropriate 5-halomethyl oxadiazole with ammonium thiocyanate. The thiocyanate-containing compounds possessed low micromolar activity against Leishmania donovani and Trypanosoma brucei, while the 5-alkyl oxadiazoles were less active against these parasites. 3-(4-Chlorophenyl)-5-(thiocyanatomethyl)-1, 2,4-oxadiazole (compound 4b) displayed modest selectivity for L. donovani axenic amastigote-like parasites over J774 macrophages, PC3 prostate cancer cells, and Vero cells (6.4-fold, 3.8-fold, and 9.1-fold, respectively), while 3-(3,4-dichlorophenyl)-5-(thiocyanatomethyl)-1,2,4-oxadiazole (compound 4h) showed 30-fold selectivity against Vero cells but was not selective against PC3 cells. In a murine model of visceral leishmaniasis, compound 4b decreased liver parasitemia caused by L. donovani by 48% when given in five daily i.v. doses at 5mg/kg and by 61% when administered orally for 5days at 50mg/kg. These results indicate that aromatic thiocyanates hold promise for the treatment of leishmanial infections if the selectivity of these compounds can be improved.
- Cottrell, Denise M.,Capers, Jeffrey,Salem, Manar M.,DeLuca-Fradley, Kate,Croft, Simon L.,Werbovetz, Karl A.
-
p. 2815 - 2824
(2007/10/03)
-
- NEW COMPOUNDS
-
The present invention relates to new compounds of formula I, (I) a process for their preparation and new intermediates prepared therein, pharmaceutical formulations containing said compounds and to the use of said compounds in therapy.
- -
-
-
- One-pot synthesis of 1,2,4-oxadiazoles mediated by microwave irradiation under solvent-free condition
-
Microwave-assisted synthesis of 1,2,4-oxadiazoles of amidoximes under solvent free conditions was found to be an efficient method for one-pot synthesis of 1,2,4-oxadiazole derivatives from amidoximes and acyl chlorides. This method is an easy, rapid, and
- Kaboudin, Babak,Navaee, Kian
-
p. 2287 - 2292
(2007/10/03)
-
- Structure-activity relationships of acyloxyamidine cytomegalovirus DNA polymerase inhibitors
-
This paper describes the structure-activity relationships of a new class of cytomegalovirus DNA polymerase inhibitors having two aryl groups joined by an acyloxyamidine linker. Examination of a series of analogues in which the terminal groups are varied r
- Tucker, John A.,Clayton, Terrance L.,Chidester, Connie G.,Schulz, Martin W.,Harrington, Leigh E.,Conrad, Steven J.,Yagi, Yoshihiko,Oien, Nancee L.,Yurek, David,Kuo, Ming-Shang
-
p. 601 - 615
(2007/10/03)
-
- Kinetics of methanolysis of substituted benzamide O-(phenoxycarbonyl)- and O-(alkoxycarbonyl)oximes catalyzed by sodium methanolate
-
The kinetics of methanolysis of substituted benzamide O-(phenoxycarbonyl)-and O-(alkoxycarbonyl)oximes catalyzed by sodium methanolate was studied at 25 °C. The reaction proceeds in two steps. In the first, faster step, the substituted phenoxy group is exchanged for a methoxy group giving rise to substituted O-(methoxycarbonyl)oximes. In the second step, a benzamide oxime is eliminated and dimethyl carbonate is formed. The slope of the plot of the rate constant in dependence on the sodium methanolate concentration has an increasing tendency in both steps. In the presence of 18-crown-6, the plots are linear and the rate constants are lower than in the absence of the crown ether. The rate constants of the reaction of the substrate with the methanolate ion and with the MeONa ion pair were determined assuming that the sodium cation-catalyzed reactions constitute the rate-determining step of the reaction of the substrate with the MeONa ion pair. For the elimination of the aryloxy group and of the substituted benzamide oxime, the rate constants of the reaction with the ion pair are roughly twelvefold and twentyfold higher, respectively, than in the uncatalyzed reaction. The slope of the dependence of log k on the pKa of the substituted phenols (β1g) has the value of -0.52 for the uncatalyzed reaction of elimination of the substituted phenoxy group, -0.83 for the elimination of the benzamide oxime group, and -0.53 for the reaction with the ion pair. In the first step and probably also in the second step, the reaction proceeds by the concerted mechanism. The relatively high ρ value of methanolysis of substituted benzamide O-(4-nitrophenoxycarbonyl)oximes, 0.63, suggests that the structure of the transition state approaches that of the tetrahedral intermediate.
- Dusek, Libor,Kavalek, Jaromir,Sterba, Vojeslav
-
p. 265 - 287
(2007/10/03)
-