Sulfuric Acid → Phthalide

Participants

Reaction Steps

According to the method of the invention, 2-(4-dibutylamino-2-hydroxybenzoyl)benzoic acid is first reacted with 4-methoxy-2-methyldiphenylamine in the presence of concentrated sulfuric acid to provide a phthalide. In this condensation reaction, the amine is used in an amount of 0.8-1.2 mols per mol of the starting benzoic acid derivative, whereas concentrated sulfuric acid is used in an amount of 1.5-8 parts by weight per part by weight of the starting benzoic acid derivative. The reaction is carried out at temperatures usually of 0°-50° C. for 5-50 hours.

Provenance & Evidence