Potassium carboxylates

Pentafluorobenzyl bromide [II] and a partially fluonnated alkyl iodide [12] react with potassium carboxylates An interesting replacement of iodine in a fluonnated alkyl iodide by an acetate group takes place with peroxyacetic acid [13] (equations 10-12)... 

Nucleophilic Attack at Halogen.- Further applications of tertiary phosphine-tetrahalogenomethane and related "reagents" have been described. The reactions of primary and secondary alcohols with potassium carboxylates in the presence of the triphenylphosphine-tetrachloromethane reagent lead to the formation of esters in good yield. However, application of this procedure... 

The mesogenic units with methylenic spacers were prepared by reacting the sodium salt of either 4-methoxy-4 -hydroxybiphenyl or 4-phenylphenol with a bromoester in DMF at 82° C for at least 4 hours in the presence of tetrabutylammonium hydrogen sulfate (TBAH) as phase transfer catalyst. In this way, ethyl 4-(4-oxybi-phenyl)butyrate, ethyl 4-(4-methoxy-4 -oxybiphenyl)butyrate, ethyl 4-(4-oxybiphenyl)valerate, ethyl 4-(4-methoxy-4 -oxybiphenyl)-valerate, n-propyl 4-(4-oxybiphenyl)undecanoate and n-propyl 4-(4-methoxy-4 -oxybiphenyl)undecanoate were obtained. These esters were hydrolyzed with base and acidified to obtain the carboxylic acids. The corresponding potassium carboxylates were obtained by reaction with approximately stoichiometric amounts of potassium hydroxide. Experimental details of these syntheses were described elsewhere (27). 

Bromobenzyl groups were introduced into PPO by radical bromination of the methyl groups. The PPO bromobenzyl groups and PECH chloromethyl groups were then esterified under phase-transfer-catalyzed reaction conditions with the potassium carboxylates just described. This procedure has been described previously (29). The sodium salt of 4-methoxy-4 -hydroxybiphenyl was also reacted with PECH (no spacer). 

After microwave heating, the potassium carboxylates 40 and 43 could be treated directly by bubbling phosgene in the aqueous solution to yield the anhydrides 41 and 44 in 85 and 67% yields, respectively, with purity >90%. 

Method C (with microwave irradiation) The alkylating agent (10 mmol) and TBA-Br or Aliquat (1 mmol) are mixed with the potassium carboxylate (10 mmol) and then placed in a microwave oven (600 W) for 2-7 min. On completion of the reaction, CH2C12 (50 ml) is added. The crude mixture is filtered through Florisil and the filtrate is evaporated to yield the ester. 

Potassium carboxylate groups introduced onto the surface of carbon fibers initiated anionic polymerization of epoxides (e.g., styrene oxide, epichlorohydrin, and glycidyl phenyl ethers) and cyclic acid anhydrides (e.g., maleic anhydride, succinic anhydride, and phthalic anhydride) in the presence of 18-crown-6 [41]. 

Naito et al.si have reported that the addition of oxirane derivatives to C02 is catalyzed by potassium carboxylates or carbonates in the presence of a crown ether cyclic carbonates (42) constitute the main product. 

Another method involves electrolysis of sodium or potassium carboxylate solutions, known as Kolbe electrolysis, in which carboxylate radicals are formed by transfer of an electron from the carboxylate ion to the anode. Decarboxylation may occur simultaneously with, or subsequent to, the formation of carboxylate radicals, leading to hydrocarbon radicals, which subsequently dimerize ... 

To 10 mmoles of potassium carboxylate were added in a Pyrex flask 10 mmol of n-octyl bromide and 1 mmol of tetraalkylammonium salt (Aliquat 336 or Bu4NBr). After shaking, the flask was introduced in the microwave oven (or in an oil bath for control experiments) for the indicated time. The temperature was measured by introducing a Quick digital thermometer in the sample just at the end of each irradiation. Organic products were recovered by a simple elution with 50 mL diethyl ether or methylene chloride and subsequent filtration over... 

Ethyl benzoate lb (0.300 g, 2.00 mmol) was added to KF/A1203 (1.00 g, 40 wt% KF) contained in a 10-mF round-bottomed flask. The mixture was stirred at room temperature to ensure efficient mixing. The flask was then fitted with a septum, placed in the microwave oven and irradiated at 100% power for 2 min (caution heating volatile materials in commercial microwave ovens for extended periods can be hazardous). After cooling, water (5 mL) was added to the solid and stirred for 10 min (to ensure the potassium carboxylate was removed from the surface) and the mixture filtered. The filtrate was neutralized by addition of aqueous HC1. The product was filtered off and dried under vacuum to afford benzoic acid 2b (0.240 g, 98%). 

Rautenstrauch, V. Potassium carboxylates by direct carbonylation of potassium alkoxides. Helv. Chim. Acta 1987, 70, 593-599. 

Potassium carboxylates. Anhydrous potassium salts of carboxylic acids can be prepared in high yield by reaction of methyl or irimethylsilyl esters or acid chlorides or fluorides with KOSi(CH,)j in an anhydrous solvent (equations I and II). Sodium or lithium carboxylates can be obtained from NaOSi(CH,)> or LiOSi(CH,)i. 

GooBen LJ, Zimmermann B, Knauber T (2008) Palladium/copper-catalyzed decarboxylative cross-coupling of aryl chlorides with potassium carboxylates. Angew Chem Int Ed 47 7103-7106... 

The alky] halide is added and the mixture stirred at 50° for 30 min. After acidification the ester is extracted with hexane. The method appears to be most satisfactory for hindered acids, since slower rates were observed in the case of pclargonic acid, CHjiCHjiyCOOH. Omission of HMFT as cosolvent results in significantly lower conversions. Sodium carboxylates tend to react more slowly than potassium carboxylates. 

MCI is then evaporated to the gas phase. The potassium carboxylate is more stable but can be deteriorated in a later step e.g. 

The reaction of potassium carboxylates with alkyl halides without the use of a solvent in the presence of catalytic amounts of a tetraalkylammonium salt proceeds smoothly to give the corresponding esters in good to excellent yields, except for cyclohexyl bromide where elimination mainly takes place. Alkylation of o- and p-hydroxybenzoic acid selectively takes place at the CO2K group. ... 

Other electrolytes that have been applied, are dimethyl sulfoxide/sodium hydride, glycol methyl ether/water/potassium carbonate or acetic acid/potassium carboxylate. ... 

---