Scheme 1. The synthesis of fused-pyrimidine derivatives. Reagents and conditions: (a) DPPA, TEA, t-BuOH, reflux; (b) CH3OCOCl, TMEDA, n-BuLi, THF; (c) TFA, DCM, rt, (d) ClSO2NCO, DCM, aq. NaOH, aq. HCl or urea, 190 °C (neat), microwave; (e) POCl3, DMF, reflux or O(POCl2)2, 145 °C, sealed tube, 2 day; (f) 4-amino-1-benzylpiperidine, DIEA, THF, rt, 24 h or 4-amino-1-benzylpiperidine, TEA, n-butanol, sealed tube, overnight; (g) cyclic amine, 185 °C (neat), microwave, 30 min.
