Fumaric acid from furfuraldehyde

An example of oxidative cleavage of a monocyclic hetero system is the conversion of furfuraldehyde into fumaric acid, a reaction that has been widely used 153 

The ability to open the furan ring by oxidation has also been utilized for synthesis of trialkylacetic acids A 2-furoic ester is first subjected to a Friedel-Crafts reaction with a tertiary alkyl halide, and the 5-alkyl-2-furoic acid obtained from the product by hydrolysis is then oxidized by alkaline permanganate to the trialkylacetic acid 154 

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