3- Furanoic acid, reaction with

The thionation of amides with phosphorus pentasulphide constitutes a traditional synthetic route to thioamides, which have been found to be especially useful for the synthesis of heterocyclic thiones containing the thiolactam grouping.However, thioformylhydroxylamine and some thioamides derived from 2-furanoic acid and anthranilic acid have also been obtained by this reaction. In the latter case, the reaction was performed in pyridine, and the authors were able to isolate the intermediate... 

The oxa-Pictet-Spengler reaction has been used with success to prepare dihydrofurano[2,3-c]pyrans and isochromans from l-(3-furyl)alkan-2-ols and 2-(3 ,4 -dihydroxy)phenylethanol, respectively. Furanyl alcohol 32 reacted with isobutyraldehyde 33 in the presence of p-toluenesulfonic acid to give the corresponding CI5-5,7-diisopropyl 4,5-dihydro-7H-furano[2,3-c]pyran 34 in good yield. ... 

A Friedel-Crafts-type reaction of phenols under basic conditions is also possible. Aqueous alkaline phenol-aldehyde condensation is the reaction for generating phenol-formaldehyde resin.34 The condensation of phenol with glyoxylic acid in alkaline solution by using aqueous glyoxylic acid generates 4-hydroxyphenylacetic acid. The use of tetraalkylammonium hydroxide instead of sodium hydroxide increases the para-selectivity of the condensation.35 Base-catalyzed formation of benzo[b]furano[60]- and -[70]fullerenes occurred via the reaction of C60CI6 with phenol in the presence of aqueous KOH and under nitrogen.36... 

Alkenylsilane acylation has been employed for the synthesis of two furano monoterpenes, dehydroel-sholzione (1) and isoegomaketone (2 Scheme 5). Acylation of isobutene with 3-methyl-2-furoyl chloride gave dehydroelsholzione in poor yield with a variety of Lewis acid catalysts (SnCU, AlCb, TiCU), but using the equivalent silane substrate, the ketone was obtained in 55% overall yield. Probably as a result of work-up conditions, the initial reaction gave a mixture of three products, the conjugated and deconjugated ketones, together with the chloro ketone addition product. Isomerization and dehydrochlorination were effected with a tertiary amine base to maximize the yield of the desired product. 

Quite recently, a new access to KDO from 1-thio-l, 2-O-isopropylidene acetal 196 has been reported [122]. Its condensation with 2-furoic acid, followed by the Tebbe methylenation afforded 198 (Scheme 42). Cyclization process was mediated by methyl triflate. Thus obtained 1-furano glycal derivative 199 was converted into KDO derivative 66 and its 2-deoxy-a-analog 200 in a reaction sequence shown in Scheme 43 [122]. 

The Feist-Benary reaction has also been used to prepare trisubstituted furanoates as well. At present, only one 2,4-disubstituted 3-furoate has been prepared using the Feist-Benary reaction. Reaction of chloroacetone with ethyl acetoacetate in cold hydrochloric acid followed by exposure to cold triethylamine provided ethyl 2,4-dimethyl-3-furoate in 54-57% yield over multiple trials. ... 

The same carbocationic intermediates are postulated in the reactivity of fuUerene epoxide with ketones and aldehydes to afford 1,3-dioxolane derivatives 12 in the presence of various Lewis acids (10P7671219,08JOC2518). In the same reaction conditions, anilines and phenols react with fiillerene oxide to afford indolino[2, 3 l,2][60]fuUerenes 13 and benzo[lt]furano[2, 3 l,2] [60]fullerenes 14, respectively (08CL1018,09ECST33). 

Effects of UV irradiation in the presence of furano-coumarins have also been studied with proteins, especially enzymes, and it is now clear that photobinding effects are not confined to nucleic acids. Both linear and angular furanocoumarins bind covalently to proteins in reactions highly dependent on structure. Enzymes are significantly inactivated, as shown in Table 1. The linear isomers appear generally to be most inhibitory, but there is great variation with the structure of both the coumarin and the protein. 

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