Scheme 1. Synthetic route of target compounds. Reagents and conditions: (i) K₂CO₃, Pd(OAc)₂, dioxane, 110 °C, 5 h; (ii) K₂CO₃, MeOH, 50 °C, reflux, 16 h; (iii) SnCl₂, AcOH, H₂O/MeOH, 90 °C, 12 h; (iv) 30%H₂O₂, NaOH, MeOH, 0–5 °C, rt, 10 h; (v) acetone, pyridine, rt, 3 h.