Sulfuric Acid → Phthalide
Reaction equation
C(N(CCCC)C1C=CC([C:10]([C:12]2[CH:20]=[CH:19][CH:18]=[CH:17][C:13]=2[C:14]([OH:16])=[O:15])=O)=C(O)C=1)CCC.CC1C=C(OC)C=CC=1NC1C=CC=CC=1.S(=O)(=O)(O)O>>[C:14]1([C:13]2[C:12](=[CH:20][CH:19]=[CH:18][CH:17]=2)[CH2:10][O:16]1)=[O:15]Participants
4
Procedure
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.