2.4- Furan dicarbonyl chloride reaction

Furan Dicarbonyl Chloride. The procedure of Kelly was employed to prepare 2,5-furan dicarbonyl chloride. To 7.8 g (0.05 mole) of 2,5-furan dicarboxylate acid in 250 ml of anhydrous ether, cooled in an ice-water bath, was added 30.0 g of 95% phosphorous pentachloride with magnetic stirring. The addition was carried out at a rate such that the reaction solution could be kept below room temperature. The reaction flask was equipped with an efficient condenser and drying tube containing calcium... 

Monosaccharides react with a variety of 1,3-dicarbonyl compounds in the presence of zinc chloride in ethanolic or aqueous solution to yield substituted furans (Scheme 69) (56MI31200). The reaction of ethyl acetoacetate with D-glucose and D-mannose yielded the trisubstituted furan (252) in 20% yield, while D-fructose under similar conditions yielded (253 7%). These products have been used for the synthesis of dehydromuscarones (63HCA1259). Oxidation of the tetrahydroxybutyl side chains with lead tetraacetate gives the aldehyde, which can be converted to the corresponding acid with alkaline silver oxide. 

On comparing the reactions of 2-amino-2-deoxyaldoses and 1-amino-l-deoxyketoses with 8-dicarbonyl compounds, which yield pyrroles (Scheme A, X = NH, A -alkyl, or A -aryl), with the reactions of the nonnitrogenous aldoses and ketoses with the same compounds, which yield furan derivatives (Scheme A, X = 0), it may be noted that the changes of bonds are the same. It seems reasonable, therefore, to assume that both processes proceed through the same, or at least similar, mechanisms. From the experimental point of view, the main differences between these two reactions concern rates and catalysts. Aldoses and ketoses react very slowly in the absence of such acidic catalysts as zinc chloride and ferric chloride. The reactions of the amino sugars are much faster and are usually performed under neutral or slightly basic conditions. 

The carbenes or carbenoids can be generated in a variety of ways. It is not always clear whether the reaction is concerted or stepwise and whether the carbene behaves as an electrophilic, nucleophilic or radical species. For instance, a carbenoid generated from bismuthonium ylide (19) in the presence of copper(I) chloride would behave as a triplet and add as a radical to a terminal alkyne" (equation 17). The dicarbonyl structure and the absence of reaction with methyl propionate to a furane might well indicate electrophilic character of this carbene. 

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