Furan-2-carboxylate, bromination

Using these assumptions and conventions, Imoto and co-workers have correlated a number of series of reactions of thiophenes and furans. The reactions studied are the acid-base equilibria pK values) and the acid catalyzed methylations (thiophenes only) of thiophene-and furan-carboxylic acids and the alkaline hydrolyses of their ethyl esters the side-chain bromination of the a-acetylthiophenes, and the a-mercuration of thiophenes and the polarographic half-wave potentials of the methyl esters of thiophene- and furan-carboxylic acids and of nitrothiophenes. The pK values were determined and the ester hydrolyses studied for all three substitution orientations in the thiophene series. For the 4-R-2-Y and 5-R-2-Y series, the p-values do not appear significantly different and the data could probably be combined into a single series unfortunately, however, no limits of accuracy are reported for the p-values, and some of the raw data are not readily available so recalculation is not easily possible. For the 5-R-3-Y series the p-values deviate considerably from the other values however, whereas they are higher for the pK values, they are lower for the ester hydrolyses, and it is possible that the differences are neither systematic nor significant. 

Using these assumptions and conventions, Imoto and co-workers have correlated a number of series of reactions of thiophenes and furans. The reactions studied are the acid-base equilibria values) and the acid catalyzed methylations (thiophenes only) of thiophene-and furan-carboxylic acids and the alkaline hydrolyses of their ethyl esters the side-chain bromination of the a-acetylthiophenes, and the a-mercuration of thiophenes and the polarographic half-wave potentials of the methyl esters of thiophene- and furan-carboxylic acids and of nitrothiophenes. The values were determined and the... 

Benzo[b]furan-2-carboxylic acids bromination, 4, 602 chloromethylation, 4, 602 from coumarins, 3, 686 IR spectra, 4, 590 methyl ester... 

Furan-2-carbonyl chloride, 5-alkyl-3,4-dichloro-synthesis, 4, 690 Furancarboxamides rotational isomerism, 4, 543 Furan-2-carboxylic acid, 5-acetylamino-ethyl ester reactions, 4, 647 Furan-2-carboxylic acid, amino-properties, 4, 708 Furan-2-carboxylic acid, 5-bromo-nitration, 4, 603, 711 Furan-2-carboxylic acid, 3-methyl-methyl ester bromination, 4, 604 Furan-2-carboxylic acid, 5-methyl-nitration, 4, 602... 

Furan-3-carboxylic acid, 2-methyl-methyl ester bromination, 4, 604 synthesis, 4, 686 Furancarboxylic acids acidity, 4, 71... 

Decarboxylation of halofurancarboxylic acids is usually carried out with copper and quinoline at 150-230 °C and the product often distills from the reaction mixture (71BSF242). Heating chloromercuriofurans with iodine and potassium iodide in water yields iodofurans. Thus 3,4-bis(chloromercurio)-2,5-dimethylfuran yields the diiodo compound (41%), and tetrakis(chloromercurio)furan yields tetraiodofuran (67%). Boiling sodium furan-2,5-dicar-boxylate with potassium iodide and iodine in water yields the diiodofuran, and 2,5-dibromofuran (78%) is similarly available from sodium 5-bromofuran-2-carboxylate, potassium bromide and bromine (74ZOR1341). 

The (aminomethyl)thiophene-2-carboxylic acid isomers were prepared from the corresponding methylthiophene-2-carboxylic acid esters, as exemplified for the 3-(aminomethyl) isomer 79 (Scheme 22))66 The 4-(aminomethyl) isomer was prepared in the same way, but with a low yield for the bromination step (7%))66,111 For the 5-(aminomethyl) isomer the bromomethyl compound was reacted with sodium azide, followed by catalytic reduction)74 The corresponding furan and pyridine analogues were prepared similarly. 

The well-known conversion of certain furans into lactones has been further studied recently. 2-Furoic acid, which was labeled in the carboxyl group, gave radioactive C02 when oxidized by bromine water to mucobromic acid.341... 

The intrinsically high reactivity of the furan nucleus is further exempUlied by the reaction of furfural with excess halogen to produce mucohalic acids incidentally, mucobromic acid reacts with formamide to provide a useful synthesis of 5-bromopyrimidine. On the other hand, with control, methyl furoate can be cleanly converted into its 5-monobromo or 4,5-dibromo derivatives hydrolysis and decarboxylation of the latter then affording 2,3-dibromofuran bromination of 3-furoic acid produces 5-bromofuran-3-carboxylic acid. ... 

The bromine/methanol (18.1.1.4) oxidation of furans to give 2,5-dialkoxy-2,5-dihydrofurans and the cycloaddition of singlet oxygen (18.7) are discussed elsewhere in this chapter. 2,5-Dialkoxy-2,5-dihydrofurans can also be obtained by electrochemical oxidation in alcohol solvents or conveniently by oxidation with magnesium monoperoxyphthalate in methanol. Reaction of furan with lead(IV) carboxylates produces... 

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