Thank you, sir. Previously, I tried the reaction using EDC·HCl, HOBt, and DIEA. However, it seems that the carboxylic acid was not activated. I monitored the reaction by TLC but did not observe any changes. As a result, I did not obtain the expected product. May I ask, how long do you usually allow for the carboxylic acid activation step?

Thank you for your suggestion. I plan to try using DIC and HOAt, and to extend the activation time of the acid before adding the aniline.