Scheme 3. Synthesis of Aryl-Substituted Oxadiazoles and Corresponding Acrylamides.

Reagents and conditions: (a) NH₂OH·HCl, NaHCO₃, EtOH, 16 h, 80 °C, 57–65%; (b) 18a, HATU, DIPEA, DMF, 1 h, 25 °C then 12 h, 80 °C, 32–45%; (c) TFA, DCM, 1 h, 0 °C–RT, 68–77%; and (d) acryloyl chloride, K₂CO₃, acetone/water, 5 h, 0 °C, 32–63%.