Formic acid as reagent for carboxylation

Formic acid as reagent for carboxylation of 1-methylcyclohexyl cation to form 1-methylcyclohexanecar-boxylic acid, 46, 72... 

An example of the separation of the anilides of the eight lowest straight-chain carboxylic acids on sodium dodecylbenzene sulphonate is shown in Fig. 5.14. The problem of the procedure described above consists in that formanilide cannot be prepared as CO, SO2 and HC1 are produced by the action of thionyl chloride on formic acid. Formanilide must, therefore, be prepared in an aqueous medium, the other acids must be extracted into a non-aqueous medium. The yield of the extraction varies considerably depending on the type of the acid, and the presence of water in the reaction medium may affect the reaction yield significantly, which makes quantitative analysis difficult. Condensates with toluidine, which were used for the determination of formic acid by GC, are prepared by an analogous procedure. As other toluidine isomers may serve as the reagents, formyl derivatives have been suggested for the separation of these substances [181]. 

The reagents used for the completion of the purine heterocycle are essentially the same as those used for the Traubc synthesis. The purine ring is formed by condensation with derivatives of formic acid or other carboxylic acids. Alternatively, formylation of the amino group is accomplished by a mixture of formic acid and acetic anhydride followed by cyclization. Alkyl esters or trialkyl ortho esters are also versatile synthons for ring closure. Moreover, heating in formamide or cyclization with urea or thiourea provides a satisfactory route. Condensations with isothiocyanates show unusual versatility leading to 2-sulfanylpurin-6-ols. From carbonic acid derivatives, cyclization is reported with chlorocarbonic esters, diethyl carbonate or carbon disulfide. 

In the box above, you can see acetone used as a solvent for an 5 2 reaction and formic acid (HCO2H) as solvent for the S l reaction. These are typical choices a less polar solvent for the Sn2 reaction (just polar enough to dissolve the ionic reagents) and a polar protic solvent for the S l reaction. The S l reaction fairly obviously needs a polar solvent as the rate-determining step usually involves the formation of ions and the rate of this process will be increased by a polar solvent. More precisely, the transition state is more polar than the starting materials and so is stabilized by the polar solvent. Hence solvents like water or carboxylic acids (RCO2H) are ideal. 

Nimura, N. Kinoshita, T. Yoshida, T. Uetake, A. Nakai, C. 1-Pyrenyldiazomethane as a fluorescent labeling reagent for liquid chromatographic determination of carboxylic acids, Anal.Chem., 1988, 60, 2067-2070. [derivatization gradient isocratic fluorescence detection LOD 20-30 fmol lactic acid formic acid propionic acid dinoprostone dinoprost alprostadil linolenic acid palmitoleic acid myristic acid linoleic acid palmitic acid oleic acid stearic acid arachidic acid]... 

The transformation of aldehydes to carboxylic acids is a fundamental reaction in organic synthesis. Many successful methods have been developed for these types of oxidations [1], but most of them have limitations as they require stoichiometric amounts of oxidants such as chlorite [2], diromium(VI) reagents [3], potassium permanganate [4], or peroxides [5]. The use of organic solvents e.g., acetonitrile, didiloromethane, cyclohexane, formic add, or benzene is also usually necessary. Despite the fact that these methods have several disadvantages, such as low selectivity and production of waste, some of them have been widely used in industry and are still in use today. The growing awareness of the environment has created a demand for efficient oxidation processes with environmentally friendly oxidants under mild conditions ( green chemistry) [6]. 

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