Diazald → Methyl 9-oxo-9H-xanthene-1-carboxylate

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Reaction Steps

Esterification of acid can be achieved by several conventional methods by those skilled in the art. These procedures include utilizing diazomethane or methyl alcohol catalyzed by mineral acids. For example, ethereal diazomethane solution can be prepared from N-methyl-N-nitrosotoluene-p-sulphonamide and potassium hydroxide from a water bath. 9-Oxoxanthene-1-carboxylic acid (1.29 g, 5 mmol) in absolute methanol is added to this ethereal diazomethane solution at 0° C. until a pale yellow color formed. Removal of the solvent provides the desired ester solid in 100% yield. Thus the final products, Examples 5-9, can be prepared by condensation hydrazine with the ketonester 11 as described in General procedure C.

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