Potassium compounds esters

In the presence of potassium tert-butylate and as with most organic compounds, esters combust spontaneousiy after a period of induction that is generally very short. Such accidents have been reported with propyl formate, ethyl acetate and dimethyl carbonate. 

The reason why the acyloin synthesis is especially characteristic of aromatic aldehydes, depends on the circumstance that in the aromatic series the tertiary carbon atom in the ring does not allow of the aldol condensation, a reaction for which conditions are otherwise much more favourable. The simplest example of the acyloin condensation, moreover, was already encountered in the case of formaldehyde (p. 218) glycollic aldehyde is the simplest acyloin. Acyloin compounds are also produced, in the aliphatic series, by the action of sodium or potassium on esters, and hence are also formed as by-products in the acetoacetic ester synthesis (Bouveault, Scheibler). 

It is known that 3-aminobenzo[6]furan can be prepared from o-cyanophenols and a-halogenocarbonyl compounds with subsequent Thorpe cyclization (73JPR779). The extension of this synthesis to heteroatom substituted benzo[6]furans is straightforward (76JPR313). The reaction of potassium salts of 3-cyano-2-pyridones (e.g. 27) with a-halogenocarbonyl compounds (esters, ketones) yields 2-alkoxy-3-cyanopyridines which can be cyclized in the presence of sodium ethoxide to give 3-aminofuro[2,3-6]pyridines (Scheme 6). 

In previous investigations the oils had been saponified by heating with a solution of caustic alkali, and the alkaline solution subsequently distilled, or shaken with a solution of either petroleum benzine or ether. In order, however, that none of the constituents should become decomposed or altered by this treatment, they took advantage of the fact that methyl salicylate combines with cold dilute solutions of the alkalies to form salts of the ester. These are quite unstable, but the potassium compound is readily soluble in water. The oils were, therefore, shaken with successive portions of a cold dilute solution of potassium hydrate, and when the oil had become reduced to about one-diird of its original volume an equal volume of ether was added, and the extraction with alkali continued until nothing more was taken up by the latter from the ether solution. After distilling off most of the ether, and the dissipation of the last traces of the latter by heating for a short time on a water-bath, the residues were we hed. The amounts were as follows —... 

Sodium and potassium hydroxides. The use of these efficient reagents is generally confined to the drying of amines (soda lime, barium oxide and quicklime may also be employed) potassium hydroxide is somewhat superior to the sodium compound. Much of the water may be first removed by shaking with a concentrated solution of the alkali hydroxide. They react with many organic compounds (e.g., acids, phenols, esters and amides) in the presence of water, and are also soluble in certain organic liquids so that their use as desiccants is very limited... 

The condensation of aldehydes and ketones with succinic esters in the presence of sodium ethoxide is known as the Stobbe condensation. The reaction with sodium ethoxide is comparatively slow and a httlo reduction of the ketonic compound to the carbinol usually occurs a shorter reaction time and a better yield is generally obtained with the more powerful condensing agent potassium ieri.-butoxide or with sodium hydride. Thus benzophenone condenses with diethyl succinate in the presence of potassium [Pg.919]

Chloroacetate esters are usually made by removing water from a mixture of chloroacetic acid and the corresponding alcohol. Reaction of alcohol with chloroacetyl chloride is an anhydrous process which Hberates HCl. Chloroacetic acid will react with olefins in the presence of a catalyst to yield chloroacetate esters. Dichloroacetic and trichloroacetic acid esters are also known. These esters are usehil in synthesis. They are more reactive than the parent acids. Ethyl chloroacetate can be converted to sodium fluoroacetate by reaction with potassium fluoride (see Fluorine compounds, organic). Both methyl and ethyl chloroacetate are used as agricultural and pharmaceutical intermediates, specialty solvents, flavors, and fragrances. Methyl chloroacetate and P ionone undergo a Dar2ens reaction to form an intermediate in the synthesis of Vitamin A. Reaction of methyl chloroacetate with ammonia produces chloroacetamide [79-07-2] C2H ClNO (53). 

Potassium fluoride [7789-23-3], KF, is the most frequently used of the alkaU metal fluorides, although reactivity of the alkaU fluorides is in the order CsF > RbF > KF > NaF > LiF (6). The preference for KF is based on cost and availabiUty traded off against relative reactivity. In its anhydrous form it can be used to convert alkyl haUdes and sulfonyl haUdes to the fluorides. The versatility makes it suitable for halogen exchange in various functional organic compounds like alcohols, acids and esters (7). For example, 2,2-difluoroethanol [359-13-7] can be made as shown in equation 9 and methyl difluoroacetate [433-53 ] as in equation 10. 

Carboxylic Acid Group. Sorbic acid undergoes the normal acid reactions forming salts, esters, amides, and acid chlorides. Industrially, the most important compound is the potassium salt because of stabiUty and high water solubiUty. Sodium sorbate [7757-81-5] (E,E form [42788-83-0]) is less stable and not commercially available. The calcium salt [7492-55-9] which has limited solubiUty, has use in packaging (qv) materials. 

The most common impurities are the corresponding acid and hydroxy compound (i.e. alcohol or phenol), and water. A liquid ester from a carboxylic acid is washed with 2N sodium carbonate or sodium hydroxide to remove acid material, then shaken with calcium chloride to remove ethyl or methyl alcohols (if it is a methyl or ethyl ester). It is dried with potassium carbonate or magnesium sulfate, and distilled. Fractional distillation then removes residual traces of hydroxy compounds. This method does not apply to esters of inorganic acids (e.g. dimethyl sulfate) which are more readily hydrolysed in aqueous solution when heat is generated in the neutralisation of the excess acid. In such cases, several fractional distillations, preferably under vacuum, are usually sufficient. 

Cellobiose was prepared first by Skraup and Konig by the saponification of the octaacetate with alcoholic potassium hydroxide, and the method was improved by Pringsheim and Merkatz.3 Aqueous barium hydroxide also has been employed for the purpose, and methyl alcoholic ammonia has been used extensively for the hydrolysis of carbohydrate acetates. The method of catalytic hydrolysis with a small quantity of sodium methylate was introduced by Zemplen,i who considered the action to be due to the addition of the reagent to the ester-carbonyl groups of the sugar acetate and the decomposition of the addition compound by reaction with alcohol. The present procedure, reported by Zemplen, Gerecs, and Hadacsy, is a considerable improvement over the original method (see Note 2). 

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... 

The elimination of water from a fluorinated compound generally follows a reaction path similar to that of its nonfluorinated counterpart, although the presence of the highly electronegative fluorine atoms may have unexpected effects Various monofluoro alcohols can be dehydrated via their tosyl esters at 75 C by using potassium rert-butoxide [80] (equation 50)... 

Works on the oxidation of uric acid has unequivocally established the triazine structure > ° (9) of oxonic acid. This is further confirmed by the straightforward synthesis described by Piskala and Gut. ° The reaction of biuret (11) with potassium ethyloxalate yielded a potassium salt (24), that with ethyl oxamate, the amide of oxonic acid (25). Both these compounds were converted to 5-azauracil. An analogous reaction with diethyloxalate which should produce an ester of oxonic acid resulted in a mixture of urethane and parabanic acid, however. 

As shovm above, the attachment of the aromatic ring to the carbon chain bearing the basic nitrogen may be accomplished through an ester or an amide configured in either direction. A simple ether linkage fulfills this function in yet another compound that exhibits local anesthetic activity. Thus, alkylation of the mono potassium salt of hydroquinone with butyl bromide affords the ether (77) alkylation of this with w-C3-chloropropyl)morpholine affords pramoxine (78)... 

Urea maybe reacted with acetoacetic ester and that product nitrated to give 5-nitro-orotec acid That is hydrogenated, then reacted with urea and potassium cyanate to give tetrahydroxypy-imidopyrimidine. The tetrahydroxy compound Is converted to the tetrachloro compound POCI3. Reaction with diethanolamine and then with piperidine gives dipyridamole. 

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