Alternative linear synthesis for subtype 12
aReagents and conditions: a) Diethylmalonate, NaOEt, EtOH, reflux, o. n., 86%; b) POCl3, BnEt3NCl, 50 °C, 6 h, 70%; c) aniline derivative, EtOH, 150 °C, 30 min, MW, 55–80%; d) DMF, 110 °C, 30 min, MW, 50–69%.