Scheme 2.
Reagents and conditions: (a) anhydrous EtOH, 0 °C, 1h; (b) phenylhydrazine, PPA, EtOH, 70 °C, 30 min; (c) CH3OH, Et3N, 60 °C, 2h; (d) NaOH, EtOH, reflux, 30 min; (e) (i) SOCl2, Et3N, reflux, 30 min.; (ii) 33% NH4OH, anhydrous THF, r.t., 15 min; (f) POCl3, 60 °C, 2h; (g) HCOONH4, 10% Pd/C, EtOH, reflux, 2 h.