Figure 5

Synthesis and chemical structures of compounds 12a–j. Reagents and conditions: (i) absolute ethanol, conc. HCl, heating under reflux, 24 h. (ii) a: MeOH/MeONa, room temp., 3 h. b: ethyl cyanoacetate, DMF, heating under reflux, 6 h. (iii) absolute ethanol, DMF, TEA, heating under reflux, 2–5 h.