Scheme 1.

Synthesis of 5,7-dibromo-2-salicyloylbenzofuran O-ether derivatives 7a–h and 8f–h. Reagents and conditions: (i) NBS, PTSA, 60 °C, 15 min., 83%; (ii) DMAP, Na₂CO₃, H₂O, 80 °C, 5 h, 72%; (iii) AlCl₃, DCM, r.t., 3 h, 89%; (iv) K₂CO₃, acetone, reflux, 8 h, 60–87%; and (v) 1. NaOH, CH₂Cl₂/CH₃OH (9:1), r.t., 1 h 2. HCl, 70–82%.