Pyridine-2,6-diacetic acid

Ethylenediamine tetraacetic acid Ethylene diamine monoacetic acid Ethylene diamine diacetic acid Ethylene diamine triacetic acid Ethylene diamine Tris(2-aminoethyl)amine Diethylenetriaminepentacetic acid 2.2.6.6- Tetramethylpiperidine 2.2.6.6- Tetramethylpiperidinol 2-(Dimethylamino) pyridine 4-(Dimethylamino) pyridine N-Butyl piperidine N,N-Diethyl cyclohexylamine... 

Piperazine-N,N -diacetic acid dithioamide refluxed 3 hrs. with p-methoxyphen-acyl bromide in abs. ethanol containing 2-3 drops of pyridine, and the product shaken 10 min. with 1 1 aq. NHg -> N,N -di- (4-p-methoxyphenyl-2-thiazolyl-methyl)piperazine. Y 91%. F. e. s. H. A. Braun, H. Kiihne, and B. Prijs, Helv. 43, 659 (1960). 

Like the pyridine aldoximes, the ketoximes give metal chelate complexes . The a f-pyridyl oxime of 2-benzoylpyridine gives such complexes whilst the n-pyridyl oxime does not. The stereochemical assignments are based on the Beckmann rearrangement of the oximes , and the behaviour of the two oximes with metal ions is that to be expected from the structures of chelates in this series . The Beckmann rearrangement has been used several times in the pyridine series 8- , The oximes prepared from 2-phenacyl-and 2,6-diphenacyl-pyridine give pyridine-2-acetic acid anilide and pyri-dine-2,6-diacetic acid dianilide, respectively, and must be the n-pyridyl compounds ". ... 

Bisa.codyl, 4,4 -(2-PyridyLmethylene)bisphenol diacetate [603-50-9] (Dulcolax) (9) is a white to off-white crystalline powder ia which particles of 50 p.m dia predominate. It is very soluble ia water, freely soluble ia chloroform and alcohol, soluble ia methanol and ben2ene, and slightly soluble ia diethyl ether. Bisacodyl may be prepared from 2-pyridine-carboxaldehyde by condensation with phenol and the aid of a dehydrant such as sulfuric acid. The resulting 4,4 -(pyridyLmethylene)diphenol is esterified by treatment with acetic anhydride and anhydrous sodium acetate. Crystallisation is from ethanol. 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

The dimethyl acetal (94) is readily prepared from the 22-aldehyde (93) by direct reaction with methanol in the presence of hydrogen chloride. Ena-mines (95) are formed without a catalyst even with the poorly reactive piperidine and morpholine.Enol acetates (96) are prepared by refluxing with acetic anhydride-sodium acetate or by exchange with isopropenyl acetate in pyridine.Reaction with acetic anhydride catalyzed by boron trifluoride-etherate or perchloric acid gives the aldehyde diacetate. 

A solution of 1 g of the diacetate (III) in lOOcc of n-heptane containing 2.5 ccof cyclopentanol and 50 mg of p-toluenesulfonic acid is heated under reflux for 20 hours. After cooling, a few drops of pyridine are added and the solvent is eiiminated by evaporation under vacuum. The residue is taken up with methanol to give 3-cyclopentyl enolether of 17a-ethvnyl-19-nortes-tosterone ecetate which, after recrystalllzation from methanol, melts at 182°C to 1B4°C. 

As previously discussed, solvents that dissolve cellulose by derivatization may be employed for further functionahzation, e.g., esterification. Thus, cellulose has been dissolved in paraformaldehyde/DMSO and esterified, e.g., by acetic, butyric, and phthalic anhydride, as well as by unsaturated methacrylic and maleic anhydride, in the presence of pyridine, or an acetate catalyst. DS values from 0.2 to 2.0 were obtained, being higher, 2.5 for cellulose acetate. H and NMR spectroscopy have indicated that the hydroxyl group of the methy-lol chains are preferably esterified with the anhydrides. Treatment of celliflose with this solvent system, at 90 °C, with methylene diacetate or ethylene diacetate, in the presence of potassium acetate, led to cellulose acetate with a DS of 1.5. Interestingly, the reaction with acetyl chloride or activated acid is less convenient DMAc or DMF can be substituted for DMSO [215-219]. In another set of experiments, polymer with high o -celliflose content was esterified with trimethylacetic anhydride, 1,2,4-benzenetricarboylic anhydride, trimellitic anhydride, phthalic anhydride, and a pyridine catalyst. The esters were isolated after 8h of reaction at 80-100°C, or Ih at room temperature (trimellitic anhydride). These are versatile compounds with interesting elastomeric and thermoplastic properties, and can be cast as films and membranes [220]. 

The scheme required to prepare the potent tri-fluoro corticoid cormethasone acetate (292) illustrates the synthetic complexities involved in some of this work. Sequential acetylation of the pregnenolone derivative 278 with first acetic anhydride in pyridine and then acetic anhydride in the presence of tosic acid affords diacetate 279. Reaction of that intermediate with nitrosyl fluoride results initially in addition of the reagent to the 5,6-olefin moiety to afford the fluoro oxime reaction with a second mole of reagent at nitrogen gives the nitroimine derivative 280 passage over alumina serves to hydrolyze the imine function to the corresponding 6-ketone (281). 

The identity of various derivatives is established by periodate titrations (41). Hydrolysis of the acetonide diacetate 6 by sulfuric acid in the presence of 2,4-dinitrophenylhydrazine (DNP) gives a small yield of the 16-acetate 10 (/). Also typical of the series, but not shown in the schemes, the C-7 alcohol group of compound 6 is oxidized to a ketone by chromium trioxide in pyridine (48,49). 

In 1942, Hann, Haskins and Hudson48 reported that the di-(o-nitro-benzylidene)-dulcitol described by Tanasescu and Macovski was not oxidized by lead tetraacetate and therefore could not possess the structure (1,2 5,6) arbitrarily assigned to it by the earlier workers. In view of the fact that the diacetal gave the known l,3,4,6-tetraacetyl-2,5-diben-zoyl-dulcitol when it was benzoylated in pyridine and then acetylated under acidic conditions, they regarded it as l,3 4,6-di-(o-nitrobenzyli-dene)-dulcitol, but of course this conclusion is not unequivocal. 

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