The title compound （C19H15NO6） was synthesized via a three-component reaction and characterized by means of IR and 1H NMR. Its crystal and molecular structures were determined by X-ray diffractometry. It belongs to the monoclinic system, space group P21/c with a = 11.670（3）, b = 12.076（3）, c = 11.613（3）, β = 99.490（4）°, V = 1614.2（7）3, Mr = 353.32, Z = 4, Dc = 1.454 g/cm3, λ = 0.71073, μ = 0.110 mm-1, F（000） = 736, the final R = 0.0503 and wR = 0.1311. A total of 8454 reflections were collected, of which 3497 were independent （Rint = 0.0333） and 2102 were observed with I 2σ（I）.
The title compound,3-acetamido-1-phenyl-4-（2,6-dichloro）benzylidene-5-pyrazolone（C18H13Cl2N3O2,Mr = 374.21）,has been synthesized by one-step condensation of 2,6-dichloroben-zaldehyde with acetic anhydride and 3-amino-1-phenyl-5-pyrazolone under microwave irradiation.The compound was characterized by means of IR and 1H NMR.Its crystal and molecular structure were determined by X-ray diffractometry.It belongs to the orthorhombic system,space group Pbca,with a = 12.5312（13）,b = 8.5495（9）,c = 31.110（3） ,V = 3332.9（6） 3,Z = 8,Dc = 1.492 g/cm3,λ = 0.71073 ,μ（MoKα） = 0.407 mm-1,F（000） = 1536,the final R = 0.0394 and wR = 0.0984.A total of 15894 reflections were collected,of which 3630 were independent（Rint = 0.0362）.There exist three planes in the molecular structure.X-ray analysis reveals that the dihedral angles between planes 1 and 2,1 and 3 and 3 and 2 are 80.89,74.29 and 20.57°,respectively.
The title compound（C26H18N4O4） has been synthesized via a three-component reaction and it was characterized by means of IR and 1H NMR.Its crystal and molecular structures were determined by X-ray diffractometry.It belongs to the triclinic system,space group P1 with a = 7.7288（15）,b = 11.168（2）,c = 12.645（3） ,α = 107.02（3）,β = 90.85（3）,γ = 101.93（3）°,V = 1017.9（3） 3,Mr = 450.44,Z = 2,Dc = 1.470 g/cm3,λ = 1.54178 ,μ = 0.836 mm-1,F（000） = 468,the final R = 0.0488 and wR = 0.1180.A total of 11903 reflections were collected,of which 3642 were independent（Rint = 0.0377） and 3025 were observed with I 2σ（I）.
Two new 1,3-oxazin derivatives, C22H24N2O5 （3I） and C19H16N2O5（3II）, have been synthesized via an unusual cascade reaction. The attractive aspect of this cascade reaction is that the novel construction of 1,3-oxazine and the direct C-N bond formation from C-C bond can be easily achieved via pyridine-mediated acylation in a one-pot operation. Both compounds have been synthesized and characterized by elemental analysis, IR, NMR spectra and X-ray single-crystal diffraction. Compound 3I crystallizes in monoclinic, space group P21/n with α = 16.282（4）, b = 7.4117（18）, c = 17.256（5） A, β = 103.193（9）°, V = 2027.4（9） A3, Mr = 396.43, Z = 4, Dc= 1.299 g/cm3, F（000） = 840, MoKa radiation （λ = 0.71073 A）, the final R = 0.0771 and wR = 0.1582 for 3662 were observed reflections with I 〉 2σ（I）. Compound 3II crystallizes in triclinic, space group Pī with α = 7.1265（9）, b = 10.1071（13）, c = 23.529（3） A, α = 97.463（9）, β = 96.981（9）, γ = 94.345（9）°, V = 1600.5（4） A3, Z = 4, Dc = 1.409 g/cm3, F（000） = 736, CuKa radiation （λ = 1.54186 A）, the final R = 0.0515 and wR = 0.1241 for 4920 observed reflections with I 〉 2σ（I）. The preliminary antibacterial activities of 2 and 3 against E. coli and S. aureuswere investigated. The results showed that the inhibiting effect of 3 was higher than that of 2.
