Scheme 2. Synthesis of Ar2 Analogues Based on the Core Scaffold of (i) Monoaryl Fragment 4 or (ii) Biaryl Fragment 5.

Reagents and conditions: (a) ethyl formate, NaOEt, EtOH, 0–90 °C, 22 h; (b) AcOH, NH₂NH₂·xH₂O, EtOH, 75 °C, 3 h; (c) aryl-boronic acid, Pd(PPh₃)₄, Na₂CO₃, 1,4-dioxane:H₂O (1:1 v/v), μw, 180 min; (d) SnCl₂·2H₂O, EtOH, 75 °C, 15 h; (e) BBr₃ (1.0 M in DCM), DCM, 0 °C, 4 h; (g) methyl 4-methoxybenzoate, NaH, THF, 60 °C, 48 h; (h) HCl (37%), NH₂NH₂·xH₂O, EtOH, 90 °C, 16 h.