- Kinetics and Mechanism for Oxime Formation from Pyridine-2-, -3-, and -4-carboxaldehydes
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Oxime formation from pyridine-2-, -3-, and -4-carboxaldehydes occurs with rate-limiting carbinolamine dehydration under both acidic and neutral conditions.Carbinolamine dehydration of pyridine-2-carboxaldehyde occurs via a transition state bearing a single positive charge, unlike the corresponding reaction for formyl-1-methylpyridinium ion and the reaction under acidic conditions for pyridine-3- and -4-carboxaldehydes.
- Malpica, A.,Calzadilla, M.,Baumrucker, J.,Jimenez, J.,Lopez L.,et al.
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- Novel access to 2-substituted quinolin-4-ones by nickel boride-mediated reductive ring transformation of 5-(2-nitrophenyl)isoxazoles
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Reductive ring transformation of 3-substituted 5-(2-nitrophenyl)isoxazoles, readily accessible via 1,3-dipolar cycloaddition of 2-ethinylnitrobenzene with nitrile oxides, opens a novel access to 2-substituted quinolin-4-ones. Nickel boride, generated in situ from nickel chloride and sodium borohydride, allows, via simultaneous reduction of the nitro group and reductive cleavage of the isoxazole ring, the one-step conversion into the target quinolin-4-ones. This protocol tolerates various functional groups, except olefins, and thus is complementary to the reductive ring transformation with iron/acetic acid, which predominantly tolerates olefins.
- Lohrer, Bernhard,Bracher, Franz
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supporting information
(2019/11/26)
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- A versatile strategy for the synthesis of 4,5-dihydroxy-2,3-pentanedione (DPD) and related compounds as potential modulators of bacterial quorum sensing
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Resistance to antibiotics is an increasingly serious threat to global public health and its management translates to significant health care costs. The validation of new Gram-negative antibacterial targets as sources for potential new antibiotics remains a challenge for all the scientists working in this field. The interference with bacterial Quorum Sensing (QS) mechanisms represents a potentially interesting approach to control bacterial growth and pursue the next generation of antimicrobials. In this context, our research is focused on the discovery of novel compounds structurally related to (S)-4,5-dihydroxy-2,3-pentanedione, commonly known as (S)-DPD, a small signaling molecule able to modulate bacterial QS in both Gram-negative and Gram-positive bacteria. In this study, a practical and versatile synthesis of racemic DPD is presented. Compared to previously reported syntheses, the proposed strategy is short and robust: it requires only one purification step and avoids the use of expensive or hazardous starting materials as well as the use of specific equipment. It is therefore well suited to the synthesis of derivatives for pharmaceutical research, as demonstrated by four series of novel DPD-related compounds described herein.
- Stotani, Silvia,Gatta, Viviana,Medda, Federico,Padmanaban, Mohan,Karawajczyk, Anna,Tammela, P?ivi,Giordanetto, Fabrizio,Tzalis, Dimitrios,Collina, Simona
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supporting information
(2018/10/20)
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- Design, synthesis, and structure-activity relationships of 3,4,5-trisubstituted 4,5-dihydro-1,2,4-oxadiazoles as TGR5 agonists
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Given its role in the mediation of energy and glucose homeostasis, the G-protein-coupled bile acid receptor1 (TGR5) is considered a potential target for the treatment of type2 diabetes mellitus and other metabolic disorders. By thorough analysis of diverse structures of published TGR5 agonists, a hypothetical ligand-based pharmacophore model was built, and a new class of potent TGR5 agonists, based on the novel 3,4,5-trisubstituted 4,5-dihydro-1,2,4-oxadiazole core, was discovered by rational design. Three distinct synthetic methods for constructing 4,5-dihydro-1,2,4-oxadiazoles and extensive structure-activity relationship studies are reported herein. Compound (R)-54n, the structure of which was determined by single-crystal X-ray diffraction and quantum chemical solid-state TDDFT-ECD calculations, showed the best potency, with an EC50 value of 1.4nM toward hTGR5. Its favorable properties invitro warrant further investigation.
- Zhu, Junjie,Ye, Yangliang,Ning, Mengmeng,Mandi, Attila,Feng, Ying,Zou, Qingan,Kurtan, Tibor,Leng, Ying,Shen, Jianhua
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supporting information
p. 1210 - 1223
(2013/07/26)
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- Synthesis and characterization of pyridyl propargyloximes
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4-Pyridiniumaldoxime and 3-pyridiniumaldoxime are synthesized by the treatment of 4- and 3-pyridinecarboxaldehydes with hydroxylamine hydrochloride, respectively. Methyl triflate salts were obtained by the treatment of methyl triflate with corresponding 4-pyridiniumaldoxime and 4-pyridinecarboxaldehyde O-propragyloxime. The reactions of 4-pyridiniumaldoxime and 3-pyridiniumaldoxime with 3-bromo-l-trimethylsilyl-l-propyne yielded the corresponding pyridinecarboxaldehyde O-propragyloximes. The structures of these products were determined by 1'H, 13C NMR data and X-ray structural analysis.
- Erenler, Ramazan
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experimental part
p. 3546 - 3548
(2012/02/02)
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- Synthetic access to new carbamate and thiocarbamate derivatives from pyridinecarbaldehyde oximes and hydroxypyridines
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The synthesis of pyridine carbamate and thiocarbamate derivates is described. A series of oxime carbamate and thiocarbamate derivatives were synthesized by the addition of 2-, 3-, and 4-pyridinecarbaldehyde oximes to isocyanates and isothiocyanates. Furth
- Kocak, Ahmet,Ahmetli, Gulnare,Kocak, Nuriye,Malkondu, Sait,Yaylaci, Aysegul,Kurbanli, Sultan
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experimental part
p. 1629 - 1637
(2011/06/23)
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- Alumina sulfuric acid mediated solvent-free and one-step Beckmann rearrangement of ketones and aldehydes and a useful reagent for synthesis of keto- and ald-oximes
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Under solvent-free conditions, one-step Beckmann rearrangement of a variety of ketones and aldehydes could proceed in the presence of alumina sulfuric acid (ASA). The ASA reagent can also be used for the preparation of keto- and ald-oximes.
- Hosseini-Sarvari, Mona,Sharghi, Hashem
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p. 205 - 208
(2007/10/03)
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- SYNTHETIC COMPOUNDS AND DERIVATIVES AS MODULATORS OF SMOKING OR NICOTINE INGESTION AND LUNG CANCER
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Disclosed are nicotine-related compounds that selectively inhibit cytochrome P-450 2A6 (CYP2A6), selectively inhibit cytochrome P-450 2A13 (CYP2A13), and/or selectively modulate a nicotinic acetylcholine receptor (nAChR). Also disclosed are pharmaceutical compositions comprising a compound of the invention, as well as methods of using the pharmaceutical compositions for treating or preventing a disease or disorder associated with nicotine-ingestion, or a disease or disorder amenable to treatment by selective modulation of nAChRs.
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Page/Page column 63
(2010/02/12)
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- Triphenylphosphine catalyzed Michael addition of oximes onto activated olefins
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A new reaction condition for Michael addition of oximes onto activated olefins has been discovered using a catalytic amount of triphenylphosphine. This is a first and milder alternative to classical base (hydroxide, alkoxide) catalyzed Michael addition of oximes. Various aldoximes 1a-h and ketoximes 2a-c (Figure 1) were reacted with different Michael acceptors such as ethyl acrylate, acrylonitrile, phenyl vinyl sulfone, methyl vinyl ketone, and 1-nitrocyclohex-1-ene to obtain the corresponding Michael adducts. About 35 different examples were attempted (Table 1 and Scheme 1); except in six cases where reactions did not produce desired products, yields varied from good to excellent. Reactions without triphenylphosphine did not proceed. A plausible mechanism of catalytic action in the present reactions is proposed (Figure 2).
- Bhuniya, Debnath,Mohan, Sankar,Narayanan, Sanju
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p. 1018 - 1024
(2007/10/03)
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- Highly efficient and catalytic conversion of aldoximes to nitriles
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(Matrix Presented) Catalytic dehydration of aldoximes can be performed highly efficiently with a catalyst system of [RuCl2(p-cymene)]2/molecular sieves under essentially neutral and mild conditions, and various types of cyano compounds are produced in good to excellent yields.
- Yang, Soon Ha,Chang, Sukbok
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p. 4209 - 4211
(2007/10/03)
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- Selective Catalytic Oxidation of Benzylic and Allylic Amines to Oximes with H2O2 over TS-1
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Catalytic system of TS-1-H2O2 combination has been shown to display remarkable reaction selectivity in the oxidation of benzylic and allylic amines to oximes in excellent yields.
- Joseph, Reni,Ravindranathan, T.,Sudalai, A.
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p. 1903 - 1904
(2007/10/02)
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- Catalytic selective oxidation of amines with hydroperoxides over molecular sieves: Investigations into the reaction of alkylamines, arylamines, allylamines and benzylamines with H2O2 and TBHP over TS-1 and CrS-2 as the new catalyst
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The liquid phase oxidation of various substituted amines with dil H2O2 and tert-butyl hydroxyperoxide (TBHP) has been investigated over titanium and chromium silicates respectively. While TS-1/H2O2 combination exhibits a remarkable activity and selectivity in the oxidation of arylamines to produce the symmetrical azoxybenzenes, CrS-2 catalyzes the selective oxidation of various substituted amines to the corresponding nitro compounds by oxidation with 70% TBHP. The nature of the reactive intermediates during the oxidation of anilines to nitrobenzenes has been established using cyclic voltammetry experiments. Further, amines possessing α C-H bonds are selectively oxidized to either oximes or the carbonyl compounds on reaction with H2O2 catalyzed by TS-1.
- Suresh,Joseph,Jayachandran,Pol,Vinod,Sudalai,Sonawane,Ravindranathan
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p. 11305 - 11318
(2007/10/02)
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- REINVESTIGATION OF NITROSATION OF METHYLPYRIDINES AND THEIR 1-OXIDES AND DEOXYGENATION OF 3-PYRIDINECARBALDEHYDE 1-OXIDE OXIME
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Treatment of methylpyridines and their 1-oxides with t-butyl nitrite in the presence of potassium t-butoxide in liquid ammonia afforded the corresponding aldoximes in good yields except for the case of 3-methylpyridine.The reaction of 3-methylpyridine with t-butyl nitrite in the presence of lithium 2,2,6,6-tetramethylpiperidide and N,N,N',N'-tetramethylethylenediamine in tetrahydrofuran at -78 deg C led to 3-(3-methyl-4-pyridyl)methylpyridine.Deoxygenation of 3-pyridinecarbaldehyde 1-oxide oxime was effected in 78percent yieldby the action of t-butyldimethylsilyl chloride-imidazolesodium iodide-zinc followed by desilylation with tetrabutylammonium fluoride to give 3-pyridinecarbaldehyde oxime.
- Tagawa, Yoshinobu,Hama, Kazuya,Goto, Yoshinobu
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p. 1605 - 1612
(2007/10/02)
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