Dicarboxylic acids ketones, cyclic, synthesis

The construction of a y-pyrone is essentially the construction of a 1,3,5-tricarbonyl compound since such compounds easily form cyclic hemiacetals then requiring only dehydration. Several methods are available for the assembly of such precursors the synthesis of chelidonic acid (4-pyrone-2,6-dicarboxylic acid) represents the obvious approach of bringing about two Claisen condensations, one on each side of a ketone carbonyl group. Chelidonic acid can be decarboxylated to produce y-pyrone itself. ... 

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