- The Aminolysis of N-Hydroxysuccinimde Esters. A Structure-Reactivity Study
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Twelwe amines, which vary substantially in basicity and steric environment around N, have been allowed to compete-in anhydrous dioxane solution-in the aminolysis of the N-hydroxysuccinimide esters of unsubstituted, p-OCH3, p-NO2, and 3,5-(NO2)2 benzoic acids.The amines, which encompass a basicity range of 6.5 pK units, display a 10000-fold variation in reactivity in their reaction with the p-NO2-ester.For the sterically unhindered amines, a Broensted-type plot of log kobsd vs. pKa has a slope of ca. 0.7.The data fit a model (Satterthwait, A.C.; Jenks, W.P.J.Am.Chem.Soc. 1974, 96, 7018-7044) in which reversible formation of a tetrahedral intermediate is followed by rate-determining breakdown to products.Appreciable sensitivity to steric factors, as evidenced from the depressed rates with α-methylbenzylamine and diethylamine, substantiates reversible formation of a crowded tetrahedral intermediate prior to the rate-determining step.The Hammett ρ values for the competitive acylation of aniline, α-methylbenzylamin, and benzylamine by substituted N-succinimidyl benzoates,are 1.4, 1.2, and 1.1, respectively.These values reflect the selectivity expected for these amines, and the substantial accumulation of charge density at the acyl C in the formation of the tetrahedral intermediate.Individual rate constants for the aminolysis of N-succinimidyl p-methoxybenzoate by n-butylamine, and by piperidine, both show first-order and second-order terms in .The general-base catalysis term is suggestive of a path involving proton transfer in the rate-determining step.
- Cline, Gary W.,Hanna, Samir B.
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- Synthesis of benzamides through direct condensation of carboxylic acids and amines in the presence of diatomite earth@IL/ZrCl4 under ultrasonic irradiation
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A green, rapid, mild and highly efficient pathway for the preparation of benzamide derivatives is reported. The reaction was performed through direct condensation of benzoic acids and amines under ultrasonic irradiation in the presence of Lewis acidic ionic liquid immobilized on diatomite earth (diatomite earth@IL/ZrCl4). A new, highly efficient and green solid acid catalyst was easily prepared via a two-step procedure and used as an effective reusable catalyst. The prepared catalyst provides active sites for the synthesis of benzamides. The advantages of this method are the use of a superior and recoverable catalyst, low reaction times, simple procedure, high-yielding and eco-friendly process and use of ultrasonic irradiation as a green and powerful technology. Since benzamides are used widely in the pharmaceutical, paper and plastic industries, and also as an intermediate product in the synthesis of therapeutic agents, the presented new synthetic methods for this type of compounds can be of considerable importance.
- Ahmadi, Masoumeh,Moradi, Leila,Sadeghzadeh, Masoud
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p. 7873 - 7889
(2018/09/27)
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- Synthesis and biological evaluation of substituted N-alkylphenyl-3,5- dinitrobenzamide analogs as anti-TB agents
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Here, a medicinal chemistry study of an N-alkylphenyl-3,5-dinitrobenzamide (DNB) scaffold as a potent anti-TB agent is presented. A series of chemical modifications were performed and forty-three new molecules were synthesized to study the structure-activity relationship (SAR) by evaluating against a sensitive strain (H37Rv) of Mycobacterium tuberculosis (MTB). Potent DNB analogs 4b, 7a, 7c, 7d, 7j, 7r and 9a were further tested against resistant strains of MTB. Their intracellular as well as bactericidal potential was also evaluated. Cytotoxicity and in vivo pharmacokinetic studies suggested that DNB analogs have an acceptable safety index, in vivo stability and bio-availability. From the present work, two compounds 7a and 7d have shown nanomolar to sub micro-molar MIC in extracellular and intracellular assays.
- Munagala, Gurunadham,Yempalla, Kushalava Reddy,Aithagani, Sravan Kumar,Kalia, Nitin Pal,Ali, Furqan,Ali, Intzar,Rajput, Vikrant Singh,Rani, Chitra,Chib, Reena,Mehra, Rukmankesh,Nargotra, Ami,Khan, Inshad Ali,Vishwakarma, Ram A.,Singh, Parvinder Pal
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p. 521 - 527
(2014/04/17)
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- Exothermic thermal reaction of dopamine with 3,5-dinitrobenzoic acid
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Pyrolysis of the crystalline 1:1 molecular complex DA·dnba, which was prepared from cocrystallization of dopamine (DA) and 3,5-dinitrobenzoic acid (dnba), was studied. This cocrystal decomposed violently at the melting-point, leading to the formation of a black solid along with a tiny amount of 3-amino-5-nitrobenzoic acid (1). The pyrolysis reaction was followed by differential scanning calorimetry (DSC) and one large exothermic peak was observed at the decomposition temperature. In view of the DSC patterns for cocrystal DA·dnba and other compounds, it seems that both a catechol moiety and an amino group of DA in addition to a strong electron acceptor such as dnba are required for the appearance of the exothermic peak. On the basis of (a) elemental analysis of the black solid and (b) other pyrolysis experiments for cocrystals PA·dnba (PA: β-phenylethylamine), BA·dnba (BA: benzylamine), DMDA·dnba (DMDA: O,O′-dimethyldopamine) and DHBA·dnba (DHBA: 3,4-dihydroxybenzylamine), it is assumed that the black solid was formed mainly through elimination of more than one molecule of water from one molecule of DA·dnba. Copyright
- Ito, Yoshikatsu,Arimoto, Satoru
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p. 849 - 857
(2007/10/03)
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