Furan-3-carboxylate

H NMR, 4, 561 <65MI31002> Benzo[b]furan-2-carboxylic acid, methyl ester UV, 4, 589 Benzo[b]furan-3-carboxylic acid, 6-chloro-4,5,7-trifluoro-2-methyl-, ethyl ester C NMR, 4, 568 <72JCS(P2)1733> Benzo[b]furan-3-carboxylic acid, 6-cyano-4,5,7-trifluoro-2-methyl-, ethyl ester C NMR, 4, 568 <72JCS(P2)1733>, 569 <72JCS(P2)1733>... 

F NMR, 4, 569 <72JCS(P2)1733> Benzo[b]furan-3-carboxylic acid, 2-methyl-, methyl ester... 

Furan-3-carboxylic acid, 5-bromo-, ethyl ester H NMR, 4, 558 <71BSF990)... 

Benzo[b]furan-3-carboxylic acid, 2-amino-esters... 

Benzo[b]furan-3-carboxylic acids methyl esters, 4, 646 Benzofuranofurans H NMR, 4, 572 5-Benzo[ b]furanol esters... 

Furan-2-carboxylic acid, 3,4,5-triphenyl-dimethyl ester, 4, 691 Furan-3-carboxylic acid, 2,3-dihydro-esters... 

Furan-3-carboxylic acid, 2-methoxy-4-methyl-methyl ester synthesis, 4, 686... 

Furan-3-carboxylic (3-furoic) acid [488-93-7] M 112.1, m 122-123°, pK 4.03 Crystd from water. 

A novel synthesis of nornicotyrine has been described by Lions and Ritchie, who condensed ethyl nicotinylacetate hydrochloride with a -dichlorodiethyl ether in presence of ammonia at — 10° to — 13° and then at room temperature, producing mainly ethyl 2-(3 -pyridyl)furan-3-carboxylate, but also some ethyl 2-(3 -pyridyl)pyrrole-3-carboxylate,... 

The last method for the preparation of 2-quinolones described in this chapter relies on a intramolecular Heck cyclization starting from heteroaryl-amides (Table 2) [57]. These are synthesized either from commercially available pyrrole- and thiophene-2-carboxylic acids (a, Table 2) or thiophene-and furan-3-carboxylic acids (b, Table 2) in three steps. The Heck cyclization is conventionally performed with W,Ar-dimethylacetamide (DMA) as solvent, KOAc as base and Pd(PPh3)4 as catalyst for 24 h at 120 °C resulting in the coupled products in 56-89% yields. As discussed in Sect. 3.4, transition metal-catalyzed reactions often benefit from microwave irradiation [58-61], and so is the case also for this intramolecular reaction. In fact, derivatives with an aryl iodide were successfully coupled by conventional methods, whereas the heteroarylbromides 18 and 19, shown in Table 2, could only be coupled in satisfying yields by using MAOS (Table 2). 

Koenig K, JR Andreesen (1991) Aerobic and anaerobic degradation of furan-3-carboxylate by Paracoccus denitrificans strain MK33. Arch Microbiol 157 70-75. 

FIGURE 10.35 Anaerobic degradation of (a) furan-2-carboxylate and (b) furan-3-carboxylate. 

An unusual rearrangement of a 3-hydroxymethyl-4-hydroxybutenolide into a furan-3-carboxylic acid occurs in the natural product, photogedunin, when it is treated with alkali the reaction is really related to some of those in sub-sections B, C, and E.llla... 

The Cu(I)-catalyzed cyclization for the formation of ethyl ( )-tetrahydro-4-methylene-2-phenyl-3-(phenylsulfonyl)furan-3-carboxylate 82 has been accomplished starting from propargyl alcohol and ethyl 2-phenylsulfonyl cinnamate. Upon treatment with Pd(0) and phenylvinyl zinc chloride as shown in the following scheme, the methylenetetrahydrofuran 82 can be converted to a 2,3,4-trisubstituted 2,5-dihydrofuran. In this manner, a number of substituents (aryl, vinyl and alkyl) can be introduced to C4 <00EJO1711>. Moderate yields of 2-(a-substituted N-tosyIaminomethyl)-2,5-dihydrofurans can be realized when N-tosylimines are treated with a 4-hydroxy-cis-butenyl arsonium salt or a sulfonium salt in the presence of KOH in acetonitrile. The mechanism is believed to involve a new ylide cyclization process <00T2967>. 

Scheme 6.92 Generation of the cephalosporin-derived cyclic allene 450 from the cephalosporin / -S-oxide triflate 449 and trapping of450 by (Z)-/J-deuterostyrene, furan, 2-acetylfuran, furan-3-carboxylic acid dimethylamide, N-tert-butoxycarbonylpyrrole, pyrrole and N-methylpyrrole.

Table 19a 13C-19F Coupling Constants" in Ethyl 6-Cyano-4,5,7-trifluoro-2-methylbenzo[6]furan-3-carboxylate...

Carbonation of lithiofurans is a useful method for obtaining these compounds. Furan-2-carboxylic acid (pKa 3.15) is a stronger acid than the 3-carboxylic acid (pKa 4.0) because of the inductive effect of the ring oxygen, and both are stronger than benzoic acid. Furancarboxylic acids can be decarboxylated by the copper-quinoline method or merely by heating. The 2-carboxylic acids are more easily decarboxylated than the 3-isomers, so furan-3-carboxylic acid can be obtained by stepwise decarboxylation of the tetracarboxylic acid via the 2,3,4-tricarboxylic acid and the 3,4-dicarboxylic acid. A more convenient source of the 3-carboxylic acid is by partial hydrolysis and decarboxylation of the readily available diethyl furan-3,4-dicarboxylate (71S545). 

Methyl benzo[6]furan-3-carboxylate is more easily hydrolyzed than its 2-isomer. 

Carboxy-4-methyl-5-pentyl-2-furanpropanoic acid (273), isolated from blood and urine, is a hitherto unknown class of metabolic compound. The structure of (273) has recently been confirmed by synthesis (80CB699). 2,4,5-Trialkyl substituted furan-3-carboxylic acids have been synthesized from acyloin and /3-ketoesters by treatment with zinc chloride. By analogy with this synthetic route, the reaction of acetoin with 3-oxoadipic acid dimethyl ester was found to yield the 2,3-dimethylfuran (274). The dimethyl ester (275) was prepared by condensation of 3-chloro-2-octanone with 3-oxoadipic acid dimethyl ester and was shown to be identical with the dimethyl ester of the natural product. 

Furan carboxylic acids are usually prepared by ring synthesis using the Feist-Benary and Paal-Knorr methods (Section 3.12.2.2). However, furancarboxylic acids can also be prepared by reaction of lithiofurans with carbon dioxide. A convenient source of furan-3-carboxylic acid (517) is the commercially available diethyl furan-3,4-dicarboxylate (518) (71S545). 

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