Synthesis and antimicrobial evaluation of novel 4-amino-6-(1,3,4-oxadiazolo/1,3,4-thiadiazolo)-pyrimidine derivatives.

A series of novel 4-amino-6-(1,3,4-oxadiazolo/1,3,4-thiadiazolo)-pyrimidine derivatives of biological interest were prepared by sequential amination, hydrazide formation, and hydrazine carbothioamidination followed by cyclization. All the synthesized compounds (6a-6h and 7a-7f) were screened for antibacterial and antifungal activity. From this group, compound 7f (MIC (µg/mL µg/mL )/Inhibition (mm): 6.25/23-30) showed good antibacterial and antifungal activity. Reagents and conditions: (a) Ethyl acetoacetate, 60% NaH, 1,4-dioxane, 60°C, 6 h; (b) DIPEA, 1,4-dioxane, 100°C, 14 h; (c) NH2NH2 ⋅ H2O, EtOH, reflux, 14 h; (d) Tolyl isothiocyanatobenzene, DMF, RT, 2 h; (e) (if X = O) EDC⋅ HCl, TEA, DMF, RT, 14 h; (f) (if X = S) Conc. H2O4, RT, 14h.