| 主权项 |
1. A method for producing a carboxylic acid anhydride comprising any one of the following steps (i) to (iii):
(i) heating a composition containing a compound represented by formula (1) in a first solvent to produce a carboxylic acid anhydride represented by formula (2): wherein in formulas (1) and (2), Y represents a divalent to hexavalent organic group, n represents an integer of 2 to 6, and m represents an integer of 1 to 3; (ii) heating a composition containing at least one compound selected from the group consisting of compounds represented by formula (3) and compounds represented by formula (4) in a second solvent to prepare a carboxylic acid anhydride represented by formula (5): wherein in formulas (3) to (5), X1 represents a residue being a tetracarboxylic acid from which four carboxy groups are removed; and (iii) heating a composition containing a compound represented by formula (6) in a third solvent to produce a carboxylic acid anhydride represented by formula (7): wherein in formulas (6) and (7), R1 represents an atom or group selected from the group consisting of a hydrogen atom, alkyl groups, halogen atoms, and a carboxy group, R2 represents an atom or a group selected from the group consisting of a hydrogen atom, alkyl groups, and halogen atoms, and X2 represents a residue of dicarboxylic acid from which two carboxy groups are removed, wherein each of the first solvent, the second solvent, and the third solvent contains an aprotic polar solvent having a boiling point of 50° C. or more. |
