Pure benzofuranone compound preparation in high yield by cyclizing salicylic acid ester then decarboxylating product

摘要

Preparation of benzofuran-3-ones (I) involves cyclizing an O-carboxymethyl-salicylic acid diester (II) using strong base then decarboxylating the obtained benzofuran-2-carboxylic acid ester (III) by successive treatment with potassium hydroxide and acid. Preparation of benzofuranones of formula (I) involves: (i) reacting a salicylic acid ether derivative of formula (II) with a strong base, optionally under a protective gas atmosphere and/or in presence of a diluent; and (ii) reacting the obtained benzofuranone carboxylic acid ester of formula (III) with potassium hydroxide, optionally in presence of a diluent, then with an acid. R1 = H, alkyl or halo; R2-R4 = alkyl.