Fused Imidazopyrazoles: Synthetic Strategies and Medicinal Applications

Scheme 26

Reagents and conditions: (a) NH₂OH, EtOH, reflux, 90 min, 70%; (b) (i) Na/EtOH, rt; (ii) MeCO₂Et, EtOH, reflux; (c) NaH, DMSO, 75–100°C, 15 min, 124b: 74% from 123; (d) (i) NaH, DMF, 75–100°C, 15 min; (ii) TBAF, THF, 0°C, rt, overnight, 124a: 43% from 123; (e) (i) NaH, DMF, 75–100°C, 15 min; (ii) TBSCl, imidazole, cat. DMAP, DMF, rt, 8 h, 124b: 55% from 123.