Pyridine reaction with acetic acid

Mixed cellulose esters containing the dicarboxylate moiety, eg, cellulose acetate phthalate, have commercially useful properties such as alkaline solubihty and excellent film-forming characteristics. These esters can be prepared by the reaction of hydrolyzed cellulose acetate with a dicarboxyhc anhydride in a pyridine or, preferably, an acetic acid solvent with sodium acetate catalyst. Cellulose acetate phthalate [9004-38-0] for pharmaceutical and photographic uses is produced commercially via the acetic acid—sodium acetate method. 

The reaction of 3-amino-4-cyanofurazan with (3-dicarbonyl compounds in the presence of catalytic amounts of nickel acetylacetonate (Ni(acac)2) gave labile enamines that on treatment with acetic acid afforded fused pyridines of type 100 in 80-95% total yields (Scheme 51) (94MC57). Eurther syntheses of furazano-pyridines can be found in the review by Sheremetev (99RCR137, 99UK154). 

The chiral acetate reagent is readily prepared from methyl mandelate [methyl (A)-hydroxy-phenyl acetate] which is first converted by treatment with phcnylmagnesium bromide into the triphenylglycol783, c (see Section 1.3.4.2.2.2.) and subsequently transformed into the acetate by reaction with acetyl chloride in the presence of pyridine. Thereby, the secondary hydroxyl group of the glycol is esterified exclusively. Both enantiomers of the reagent are readily accessible since both (R)- and (5)-hydroxyphenylacelic acid (mandelic acids) arc industrial products. 

These reactions are most important for the preparation of acyl fluorides. " Acyl chlorides and anhydrides can be converted to acyl fluorides by treatment with polyhydrogen fluoride-pyridine solution" or with liquid HF at — 10°C. Formyl fluoride, which is a stable compound, was prepared by the latter procedure from the mixed anhydride of formic and acetic acids. Acyl fluorides can also be obtained by reaction of acyl chlorides with KF in acetic acid or with DAST. Carboxylic esters and anhydrides can be converted to acyl halides other than fluorides by the inorganic acid halides mentioned in 10-77, as well as with PhsPXa (X = Cl or but this is seldom done. Halide exchange can be carried out in a... 

In much the same vein, acetylation of optically active cf-norgestrel by means of acetic anhydride and tosic acid gives the 17-acetate (72). Reaction with hydroxylamine hydrochloride in pyridine affords the orally active progestin dexnorgestrel acetime (73). ... 

Reactions of 2-methylthio-1,3-dithiolium salts with active methylene compounds have been extensively reported and reviewed. They are performed in refluxing ethanol, acetic acid, or acetonitrile, pyridine being used as catalyst. Reagents frequently used include ethyl cyanoacetate, acetyl-... 

Esters. Acetylation. The most studied of all the chemical modification treatments for wood has been acetylation. The early work was done with acetic anhydride catalyzed with pyridine (25) or zinc chloride (26). In the reaction with acetic anhydride, acetylation occurs, and acetic acid is split out as a by-product ... 

When a-vinylbenzyl alcohol reacts with bromine in dry CHC13, CC14, or CS2, (l,2,3-tribromopropyl)benzene is formed exclusively however, carrying out the reaction with pyridine hydrobromide dibromide in glacial acetic acid at 12-15° leads mainly to addition of bromine, which results in <%-(l,2-dibromo-ethyl)benzyl alcohol.70 Analogously, but without a solvent, allyl alcohol gives 2,3-dibromo-1 -propanol.71... 

ROSi CH )3 ROCOR. Trimethylsilyl ethers are converted into acetates by reaction with acetic anhydride-pyridine with catalytic amounts of 48% HF or BFa etherate ca. 85% yield). Esters of other acids are obtained similarly by use of the anhydride and HF or BF3 etherate as catalyst. ... 

The employment of suitable organic solvents, such as acetonitrile and acetic acid, with oxidation-resistant supporting electrolytes permits the anodic formation of reactive radical cations from many organic materials. Most aromatic compounds and olefins, as well as those alkanes which have particularly weak C—H bonds, are oxidised in acetonitrile containing fluoroborate or hexafluorophosphate electro-lytes. °" 2 Some aromatic radical cations can be further oxidised to dications within the available potential range. Radical cations in general either deprotonate or attack nucleophiles present in the medium reactions with pyridine, methanol, water, cyanide ion, acetate ion or acetonitrile itself produce addition or substitution products. The complete reactions involve a second electron transfer and coupled chemical... 

Several methyl esters were synthesized by the treatment of pyridine acetic adds with diazomethane. A variety of C-21 steroidal alco-hols " and the following alcohols have been employed in esterification reactions with pyridine side-chain acids. ... 

Additional organic acids can also be separated in this system, e.g., tartaric with a probable Rp of 0.22, succinic with an approximate Rp of 0.74, and fumaric with an approximate Rp of 0.89. Tricarboxylic acids can also be detected by reaction with pyridine-acetic anhydride (7 3) where citric acid gives a yellow color and other acids give either brown or brown-yellow colors (Harborne, 1984). 

The most common reaction of esterification is starch acetylation. The oldest methods of starch acetylation consisted mainly in heating starch with acetic acid anhydride in pyridine or ice-cold acetic add. This method of acetylation was applied by, among others, Twele [22, 61, 73]. Contemporarily, starch acetates are usually produced as a result of reaction run in a water suspension by exposing starch to acetic acid anhydride. All of the hydroxyl groups could react with acetic anhydride. One of the three possible products is shown in Figure 7.1. 

All these facts can be utilized in the application of the color test. Generally, the reaction is carried out in different solvents, sometimes with the addition of pyridine. Phenols can be differentiated according to the strength with which they form chelate bonds in the presence of acetic acid or with a suspension of ferric hydroxide in water or methanol with subsequent acidification. A list of chelate-forming substances is given in Table 5. 

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