Method for the preparation of derivatives of 5-hydro xy-2-carboxychromone

Abstract

Abstract WHEREIN X is an aliphatic alkyl having from C3 to C7 with its chain possibly interrupted by an oxygen atom and preferably containing a secondary alcoholic grouping, by alkaline hydrolysis of the corresponding lower alkyl ester, the latter being prepared starting from the corresponding bis-phenoxy derivative (a) by double Claisen reaction with an alkyl oxalate in the presence of an alkali metal alcoholate as the catalyst, and (b) by cyclizing the intermediate thus obtained in an acidic environment, the improvement consisting in that the reaction with the alkyl oxalate is carried out in an alcoholic protic solvent in the presence of stoichiometric amounts of the alkali metal alcoholate at a temperature not above 50*C and for a time not longer than 3 hours, the cyclization being carried out by adding an anhydrous mineral acid to the reaction mass. By so doing, the preparation of the expected compounds is cheaper, quicker and gives virtually quantitative yields. A method for the preparation of derivatives of the 5-hydroxy-2carboxychromone is disclosed, said derivatives having the general formula

Inventors

• 👤 G Pifferi

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