Scheme 2.

Synthetic pathway of compounds 22–39 ^a. ^a Reagents and conditions: (i) COCl₂, DIPEA, appropriated amine, CH₂Cl₂, r.t., 10%–99%; (ii) S₈, morpholine, DMF, 39%–62%; (iii) morpholine, K₂CO₃, MeCN, r.t., 34%; (iv) NaBH₄, MeOH, r.t., 52%; (v) (1) POCl₃, MeCN, 50 °C, (2) aniline, DIPEA, 0 °C to r.t., 53%; (vi) 4-amino-morpholine, MgSO₄, CH₂Cl₂, r.t., 78%; (vii) 4-amino-morpholine, CH₂Cl₂, r.t., 76%–80%; (viii) (1) CS₂, Et₂O, r.t., (2) (thiocyanatomethyl)benzene, ACN, r.t., 42%; (ix) morpholine-4-carbonyl chloride, DIPEA, CH₂Cl₂, r.t., 89%. (x) Appropriated amine, Et₃N, r.t., 83%–85%.