Hydroxamic acids benzo

Benzamides e.g. MS-275 8 are one of the more common hydroxamic acid alternatives but are often less potent. Recent exceptions to this pattern include substituted pyridyl [29] and thiazolyl [30] benzamides, such as 9 and 10 with HDAC1 enzyme IC50s of 19nM and 29 nM, respectively and series of benzamides substituted with other heterocycles, such as indazoles [31] and benzo [l,2,4]thiadiazines [32], many with HDAC2 IC50s of <50 nM. The addition of... 

Acylhydrazides of anthranilic acid (35, R = NHCOR ) give 3-acylamino-l,2,3-benzotriazin-4(3H)-ones (10, R = NHCOR on treatment with nitrous acid. The triazine hydroxamic acid (40) and its benzo-substituted derivatives are available by diazotization of the corresponding o-aminobenzohydroxamic acids. The pyrido[2,3-e]triazine analog (41) was prepared similarly from 3-aminoisonicotino-hydroxamic acid, but the isomeric 2-aminonicotinohydroxamic acid failed to react under the same conditions to give 42. ... 

Pal and Kapoor74 have studied the reactions of isopropoxides of aluminum, titanium and zirconium with benzo- and phenylaceto-hydroxamic adds in anhydrous benzene. Solid products of the types Al(OPr )3 L and M(OPri)4 L (where M = Ti or Zr and L is the hydroxamic acid) have been isolated all the aluminum and zirconium products are white in colour whereas titanium ones are yellow. The mixed isopropoxide hydroxamates interchange their isopropoxy group with r-but-oxy groups, yielding r-butoxide products. 

Dutta and Satapathi81 have described the synthesis of a variety of phenylmercury(II) complexes with benzo-, p-chlorobenzo-, picolino-, quinolino- and quinoline-8-hydroxamic acids and characterized them by their IR spectra and conductivity measurements. 

Rearrangements. Hurd and Bauer" added tosyl chloride in chloroform to a suspension of the sodium salt of benzohydroxamic acid (1) in the same solvent, noted a vigorous reaction, and characterized the product as benzo-(phenylcarbonyl-hydroxamic) acid (6). They postulate that the initial product is the tosylate (3), that this is a much stronger acid than (1) and so abstracts sodium from the salt (2) to give the salt (4), which undergoes concerted cleavage and Lessen rearrangement to phenylisocyanate (5) and sodium tosylate. The phenylisocyanate is then captured by (1) to yield the final product (6). 

Formation constants of 3d metal ions with A-m-tolyl-p-substituted benzohydroxamic acids and of rare earths with thenoylhydroxamic acid have been determined. Formation constants of proton and metal complexes of iV-phenyl-2-thenoyl- and A-p-tolyl-2-thenoyl-hydroxamic acids have also been determined. In addition, study has been made of the mixed ligand complexes involving nicotine- and isonicotino-hydroxamic acids. A method of extraction and spectrophotometric determination of vanadium with chlorophenylmethylbenzohydroxamic acid has also been published. It may be mentioned that hydroxamic acids (in particular, the A-phenylbenzohydroxamic acid) have been widely used as analytical reagents for metal ions. Solvent extraction of titanium by benzo- or salicyl-hydroxamic acid in the presence of trioctylamine in the form of coloured complexes has been reported. A-w-Tolyl-p-methoxybenzohydroxamic acid has been used for extraction and spectrophotometric determination of Mo and W from hydrochloric acid media containing thiocyanate. 

Pre-treatment with desferrioxamine protected human fibroblast (cell line GM 05757) monolayer cultures from cytotoxicity and genotoxicity (singlestrand breaks) induced by the pentachlorophenol (PGP) metabolite, tetrachlorohydroquinone (Witte et al. 2000). Similar pattern of protection were also observed for three other hydroxamic acids aceto-, benzo-, and salicylhydroxamic acid. Dimethylsulphoxide, an efficient hydroxyl radical scavenger, provided only partial protection even at high concentrations. In vitro studies showed that... 

Inhibition of Copper by Benzo-Hydroxamic Acids of Systematically Changed Structure... 

Benzo-hydroxamic acid derivatives are excellent chelating agents for mono-, bi-, and trivalent metals (Kurzak et al., 1990), thus offering the potential for corrosion inhibition. In the presence of a series of benzo-hydroxamic acids of systematically changed structure, the influence of substituents on the corrosion inhibiting efficiency was studied in neutral solution. 

The effect of organic inhibitors on localized or general corrosion also depends on the stability of inhibitors in the presence of different anions. In chloride-containing electrolytes, the effectiveness of many inhibitors is lower due to deterioration of the chloride ion. The influence of benzo-hydroxamic acid derivatives on copper corrosion in chloride-containing solutions was studied by different techniques. In addition to generally applied... 

If the copper was immersed in a sodium chloride solution with or without benzo-hydroxamic acid (BHA) derivatives, a thick layer was formed on the metal surface, which consisted of copper oxide, chloride, and the inhibitor molecule. The results revealed that the curve representing the aggressive solution showed two semi-circles which characterize the anodic reaction involving mass transfer through the copper oxide layer. The semi-circle at a higher frequency is due to the modulation for cop-per(I)chloride adsorbed at the electrode, while the low frequency part represents the diffusion process at the electrode due... 

Figure 9-14. Nyquist plots of copper in 0.1 M sodium chloride solution with or without benzo-hydroxamic acid derivatives [0.5 M NaCl (pH 6.5), 1 x 10 M benzo-hydroxamic acids BHA benzo-hydroxamic acid, o-Cl o-chloro, p-Cl pora-chloro o-M ortAo-methyl p-N p ra-nitro].

All derivatives of the benzo-hydroxamic acid inhibited copper corrosion more effectively than BHA itself. The efficiency was affected much more by hydrophobic bulkiness in the phenyl ring than by the electronpushing or electron-attracting character of the substituents. The results attained by electrode impedance spectroscopy and quartz crystal nanobalance techniques led to recognition that the higher efficacy was not due to the inductive effect of the substituents, as both chloro and methyl substitution led to enhanced inhibition. The most important factor is the hydrophobic bulkiness. In the inhibition process, the inhibitor molecule is attached to the copper surface by the polar group (CON"), and the apolar hydro-phobic moiety may block the metal surface... 

Benzo-hydroxamic acid derivatives inhibited the scale formation less effectively (10-22%) than phosphonic and/or carboxylic acids. 

The efficiency of benzo-hydroxamic acid derivatives, which are effective copper inhibitors for pitting and general corrosion processes, increases with increasing hydro-phobicity. The adsorption model of these compounds can be described as follows The molecule is attached to the metal surface by the unpaired electrons of the nitrogen and oxygen atoms of the hydroxamic moiety and by the n electron cloud of the phenyl ring, which may interact with the empty d-orbital of iron. 

King prepared TV-ethoxycarbonylisoxazolidine by the base-catalyzed condensation of 1,3-dibromopropane with /V-hydroxyurethane, which was decarbethoxylated by hydrochloric acid to give the parent isoxazo-licjine (l).5 If 1,3-dibromopropane is treated with potassium benzo-hydroxamate, /V benzoylisoxazolidine is obtained.149... 

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