PURPOSE: To recover the titled compound easily in producing the titled compound from an aniline and maleic anhydride with a phosphorus oxide and a specific solvent, by distilling a specific amount of the solvent from the reaction mixture after completing the reaction, and separating the phosphorus compound in the liquid phase.
CONSTITUTION: A compound of the formula (R1WR5 are H, halogen, 1W6C alkyl, aromatic group, aralkyl, 1W6C alkyl ether, OH, aryloxy, COOH or NO2) is reacted with maleic anhydride or a derivative thereof in the presence of a phosphorus oxide (dehydration and imide ring closing agent) in a solvent capable of dissolving the above-mentioned oxide and the titled compound, and the solvent is then distilled from the reaction mixture. The amounf of the residual solvent is concentrated to ≤30wt%, particularly ≤20wt%. Thus, the above-mentioned residual material is separated into the liquid phase of the phosphorus compound and the solution phase of the reaction product. The phosphorus compound is easily recovered from the former, and the titled compound useful as a raw material for heat-resistant polymers, etc. is obtained in improved yield from the latter.
FUSE TATSUJI
AYA TOSHIHIKO
