6-Benz-yloxy-2-phenyl-pyridazin-3(2H)-one.

In the title compound, C(17)H(14)N(2)O(2), the central pyridazine ring forms dihedral angles of 47.29 (5) and 88.54 (5)° with the benzene rings, while the dihedral angle between the benzene rings is 62.68 (6)°. In the crystal, molecules are linked by two weak C-H⋯O hydrogen bonds and three weak C-H⋯π inter-actions.

rac-Ethyl 4-hy-droxy-4-trifluoro-methyl-6-(2,4,5-trimeth-oxy-phen-yl)-2-thio-1,3-diazinane-5-carboxyl-ate.

In the title compound, C(17)H(21)F(3)N(2)O(6)S, the hexa-hydro-pyrimidine ring adopts a half-chair conformation: the mean plane formed by the ring atoms excluding the C atom bonded to the eth-oxy-carbonyl group has an r.m.s. deviation of 0.0427 Šand forms a dihedral angle of 66.41 (5)° with the benzene ring. The mol-ecular conformation is stabilized by an intra-molecular hydroxyl O-H⋯O(carbox-yl) hydrogen bond, generating an S(6) ring. In the crystal, pairs of N-H⋯S and N-H⋯O hydrogen bonds give rise to the formation of two-dimensional networks lying parallel to the ab plane, which incorporate graph-set motifs R(2) (2)(8) and R(2) (2)(16), respectively.

2-Benzyl-6-benz-yloxypyridazin-3(2H)-one.

In the title compound, C(18)H(16)N(2)O(2), the central pyridazine ring forms dihedral angles of 77.08 (5)° and 84.62 (5)° with the two benzene rings. The dihedral angle between the two benzene rings is 68.18 (4)°. A very weak intra-molecular C-H⋯N hydrogen bond and an intra-molecular C-H⋯π inter-action occur. The crystal structure is stabilized by weak inter-molecular C-H⋯O hydrogen bonds and weak C-H⋯π and π-π stacking inter-actions [centroid-centroid distance = 3.6867 (10) Å].

1,3-Bis(4-meth-oxy-benz-yl)-6-methyl-pyrimidine-2,4(1H,3H)-dione.

The title compound, C(21)H(22)N(2)O(4), was prepared by reaction of 6-methyl-pyrimidine-2,4(1H,3H)-dione and 1-chloro-methyl-4-meth-oxy-benzene. In the title mol-ecule, the central pyrimidine ring forms dihedral angles of 62.16 (4) and 69.77 (3)° with the two benzene rings. In the crystal, weak inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into chains.

6-Hy-droxy-4-(pyridin-3-yl)-5-(2-thienyl-carbon-yl)-6-trifluoro-meth-yl-3,4,5,6-tetra-hydro-pyrimidin-2(1H)-one.

In the title compound, C(15)H(12)F(3)N(3)O(3)S, the pyrimidine ring adopts a half-chair conformation with the mean plane formed by the ring atoms excluding the C atom bonded to thio-phene-2-carbonyl group lying nearly perpendicular to the pyridine and thio-phene rings, making dihedral angles of 84.91 (4) and 87.40 (5)°, respectively. The dihedral angle between the pyridine and thio-phene rings is 54.44 (5)°. The crystal structure is stabilized by inter-molecular O-H⋯O and N-H⋯N hydrogen bonds and weak C-H⋯O inter-actions further consolidate the structure.