Synthesis, characterization and biological evaluation of dihydropyrimidine derivatives.

A series of dihydropyrimidines containing quinoline were prepared under conventional heating and microwave irradiation. The structures of newly synthesized compounds were established based on analytical and spectral studies. Further these compounds were evaluated for their antioxidant, antifungal and antibacterial activities. Most of the compounds showed moderate to good activity when compared with standard.

Regioselective reaction: synthesis and pharmacological study of Mannich bases containing ibuprofen moiety.

A series of 4-[(4-aryl)methylidene]amino-2-(substituted-4-ylmethyl)-5-{1-[4-(2-methylpropyl)phenyl]ethyl}-2,4-dihydro-3H-1,2,4-triazole-3-thione (6) were synthesized from an arylpropionic acid namely, ibuprofen by a three-component Mannich reaction. Aminomethylation of 4-[(4-aryl)methylidene]amino-5-{1-[4-(2-methylpropyl)phenyl] ethyl}-4H-1,2,4-triazole-3-thiol (5) with formaldehyde and a secondary amine furnished this novel series of Mannich bases (6). Both Schiff bases (5) and Mannich bases (6) were well characterized on the basis of IR, NMR, mass spectral data and elemental analysis. They were screened for their anti-inflammatory, analgesic, antibacterial and antifungal activities. Some of the Mannich bases (6) carrying morpholino and N-methylpiperazino residues were found to be promising anti-inflammatory and analgesic agents.

2-(4-Isobutyl-phen-yl)-N'-[1-(4-nitro-phen-yl)ethyl-idene]propanohydrazide.

The mol-ecule of the title compound, C(21)H(25)N(3)O(3), exists in a trans configuration with respect to the ethyl-idene unit. The dihedral angle between the two substituted benzene rings is 86.99 (7)°. The nitro group is twisted from the attached benzene ring at an angle of 17.02 (7)°. In the crystal structure, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds in a face-to-face manner into centrosymmetric dimers. These dimer units are further linked into chains along the c axis by weak C-H⋯O inter-actions. These chains are stacked along the b axis. The crystal is further stabilized by weak C-H⋯π inter-actions.

3-{1-[4-(2-Methyl-prop-yl)phen-yl]eth-yl}-1-(morpholinometh-yl)-4-(4-nitro-benzyl-ideneamino)-1H-1,2,4-triazole-5(4H)-thione.

The title ibuprofen-containing Mannich derivative, C(26)H(32)N(6)O(3)S, crystallizes with two independent mol-ecules in the asymmetric unit. The morpholine ring in each mol-ecule adopts a chair conformation. The 1,2,4-triazole ring forms dihedral angles of 2.13 (10) and 75.52 (10)° with the two substituted benzene rings in one mol-ecule, with corresponding values of 19.36 (11)° and 89.03 (10)° in the other. The nitro groups are twisted from the attached benzene ring in each mol-ecule. In the crystal packing, mol-ecules are linked into supra-molecular chains via weak C-H⋯O, C-H⋯N and C-H⋯S inter-actions, and C-H⋯π and N-O⋯π links also occur.

3-[1-(4-Isobutyl-phen-yl)eth-yl]-1H-1,2,4-triazole-5(4H)-thione.

In the title compound, C(14)H(19)N(3)S, the dihedral angle between the mean planes of the five- and six-membered rings is 74.69 (4)°. Pairs of inter-molecular N-H⋯S inter-actions link neighbouring mol-ecules into dimers with R(2) (2)(8) ring motifs. These dimers are then linked together by the same type of inter-actions into an infinite one-dimensional chain along the b axis.

1-[2-(4-Isobutyl-phen-yl)propano-yl]thiosemicarbazide.

In the title compound, C(14)H(21)N(3)OS, inter-molecular N-H⋯O inter-actions generate ten-membered rings with R(2) (2)(10) ring motifs, whereas N-H⋯S inter-actions generate eight, 14- and 16-membered rings with R(2) (2)(8), R(4) (4)(14) and R(4) (4)(16) ring motifs, respectively. There are weak intra-molecular N-H⋯π inter-actions which might influence the conformation of the mol-ecule. The compound has a stereogenic center but the space group is centrosymmetic so the mol-ecule exists as a racemate.

N'-[(E)-4-Bromo-benzyl-idene]-2-(4-isobutyl-phen-yl)propanohydrazide.

The asymmetric unit of the title compound, C(20)H(23)BrN(2)O, contains two independent mol-ecules (A and B), in which the orientations of the 4-isobutyl-phenyl units are different. The dihedral angle between the two benzene rings is 88.45 (8)° in mol-ecule A and 89.87 (8)° in mol-ecule B. Mol-ecules A and B are linked by a C-H⋯N hydrogen bond. In the crystal, mol-ecules are linked into chains running along the a axis by inter-molcular N-H⋯O and C-H⋯O hydrogen bonds. The crystal structure is further stabilized by C-H⋯π inter-actions. The presence of pseudosymmetry in the structure suggests the higher symmetry space group Pbca. However, attempts to refine the structure in this space group resulted in a disorder model with high R (0.097) and wR (0.257) values. The crystal studied was an inversion twin with a 0.595 (4):0.405 (4) domain ratio.

N'-[(E)-4-Chloro-benzyl-idene]-2-(4-isobutyl-phen-yl)propanohydrazide.

The asymmetric unit of title compound, C(20)H(23)ClN(2)O, consists of two crystallographically independent mol-ecules (A and B) in which the orientations of the 4-isobutyl-phenyl units are different. The isobutyl group of mol-ecule B is disordered over two positions with occupancies of 0.850 (5) and 0.150 (5). The dihedral angle between the two benzene rings is 88.70 (9)° in mol-ecule A and 89.38 (9)° in mol-ecule B. The independent mol-ecules are linked together into chains along [100] by N-H⋯O and C-H⋯O hydrogen bonds, and by C-H⋯π inter-actions. In the chain, N-H⋯O and C-H⋯O hydrogen bonds generate R(2) (1)(6) ring motifs. In addition, C-H⋯N hydrogen bonds are observed. The presence of pseudosymmetry in the structure suggests the higher symmetry space group Pbca but attempts to refine the structure in this space group resulted in high R (0.119) and wR (0.296) values.

Ethyl 4-(5-chloro-3-methyl-1-phenyl-1H-pyrazol-4-yl)-6-methyl-2-oxo-1,2,3,4-tetra-hydro-pyrimidine-5-carboxyl-ate.

In the title compound, C(18)H(19)ClN(4)O(3), the dihydro-pyrimidin-one ring adopts a flattened boat conformation. The dihedral angle between the phenyl and pyrazole rings is 43.39 (6)°. An intra-molecular C-H⋯O contact generates an S(8) ring motif that stabilizes the mol-ecular conformation and precludes the carbonyl O atom of the ester group from forming inter-molecular inter-actions. Mol-ecules are linked into centrosymmetric dimers by pairs of N-H⋯O hydrogen bonds and the dimers are linked into infinite chains along [101] by N-H⋯N hydrogen bonds.

4-{[(E)-(4-Chloro-phen-yl)methyl-idene]amino}-3-{2-[4-(2-methyl-prop-yl)phen-yl]eth-yl}-1H-1,2,4-triazole-5(4H)-thione.

The asymmetric unit of the title compound, C(21)H(23)ClN(4)S, contains nine crystallographically independent mol-ecules, labelled A to I. The orientation of the 2-[4-(2-methyl-prop-yl)phen-yl]ethyl unit with respect to the rest of the mol-ecule is significantly different in mol-ecules E, F, H and I compared to the other independent mol-ecules. The isobutyl group of mol-ecule B is disordered over two orientations, with occupancies of 0.764 (7) and 0.236 (7). The benzene rings of the chloro-phenyl and methyl-propyl-phenyl units form dihedral angles of 21.90 (11) and 71.47 (11)°, respectively, with the triazole ring in mol-ecule A [9.15 (11) and 80.37 (11)° in B, 7.14 (11) and 84.06 (11)° in C, 25.76 (11) and 76.59 (11)° in D, 13.68 (11) and 76.82 (10)° in E, 8.38 (11) and 69.77 (10)° in F, 30.34 (11) and 78.12 (11)° in G, 21.20 (11) and 71.58 (10)° in H, and 27.65 (11) and 65.23 (11)° in I]. In each independent mol-ecule, a C-H⋯S hydrogen bond is observed. The crystal packing is stabilized by N-H⋯S and C-H⋯S hydrogen bonds, and by C-H⋯π inter-actions involving the methyl-propyl-phenyl ring.

4-[(E)-4-Bromo-benzyl-ideneamino]-3-[1-(4-isobutyl-phen-yl)eth-yl]-1H-1,2,4-triazole-5(4H)-thione.

In the title compound, C(21)H(23)BrN(4)S, the 4-bromo-benzyl-idene group is disordered over two orientations with occupancies of 0.504 (5) and 0.496 (5). One of the methyl groups of the isobutyl unit is disordered over two sites with occupancies of 0.751 (19) and 0.249 (19). The benzene rings of the isobutylphenyl and bromo-phenyl (major disorder component) groups form dihedral angles of 71.63 (11) and 21.8 (3)°, respectively, with the triazole ring. In the crystal, centrosymmetrically related mol-ecules exist as centrosymmetric N-H⋯S hydrogen-bonded dimers.

4-[(E)-4-Methoxy-benzyl-ideneamino]-3-{1-[4-(2-methyl-prop-yl)phen-yl]eth-yl}-1H-1,2,4-triazole-5(4H)-thione.

In the title compound, C(22)H(26)N(4)OS, the benzene rings of the (2-methyl-prop-yl)phenyl and 4-methoxy-phenyl units form dihedral angles of 66.85 (3) and 25.96 (3)°, respectively, with the triazole ring. The dihedral angle between the two benzene rings is 87.42 (2)°. The -CH(CH(3)) linkage is disordered over two orientations with occupancies of 0.907 (3) and 0.093 (3). An intra-molecular C-H⋯S hydrogen bond generates an S(6) ring motif. Inter-molecular N-H⋯S hydrogen bonds and C-H⋯π inter-actions are observed.

N'-[(Z)-4-(Dimethyl-amino)benzyl-idene]-4-nitro-benzohydrazide mono-hydrate.

In the asymmetric unit of the title compound, C(16)H(16)N(4)O(3)·H(2)O, there are two symmetry-independent hydrazide mol-ecules with almost identical geometries, and two independent water mol-ecules. The dihedral angles between the two benzene rings in the two hydrazide mol-ecules are 0.11 (5) and 0.77 (5)°. In one mol-ecule, an intra-molecular C-H⋯O hydrogen bond generates a ring of graph-set motif S(5). Inter-molecular N-H⋯O, O-H⋯O, O-H⋯N and C-H⋯O hydrogen bonds and π-π stacking inter-actions between the benzene rings [centroid-centroid distances in the range 3.5021 (6)-3.6403 (6) Å] are observed, together with O⋯O [2.7226 (11) Å], O⋯N [2.7072 (10) Å] and N⋯O [2.7072 (10)-2.8582 (12) Å] short contacts. The hydrazine mol-ecules are stacked along the b axis and adjacent mol-ecules are linked by water mol-ecules.

N'-[(E)-1-Phenyl-ethyl-idene]benzo-hydrazide.

The title compound, C(15)H(14)N(2)O, crystallized with two independent mol-ecules in the asymmetric unit. Both mol-ecules are non-planar and have an E configuration with respect to the C=N bond. The dihedral angles between the two benzene rings are 11.1 (2)° in one mol-ecule and 12.40 (19)° in the other. In the crystal structure, the mol-ecules are linked by N-H⋯O hydrogen bonds and weak C-H⋯O inter-actions into infinite one-dimensional chains along [1 0 0]. The crystal structure is further stabilized by N-H⋯O hydrogen bonds, weak C-H⋯O and very weak C-H⋯π inter-actions.

3-Ethyl-6-{1-[4-(2-methyl-prop-yl)phen-yl]eth-yl}-1,2,4-triazolo[3,4-b][1,3,4]thia-diazole.

In the mol-ecule of the title compound, C(17)H(22)N(4)S, the triazolothia-diazole ring system is essentially planar and forms a dihedral angle of 74.34 (6)° with the benzene ring. In the crystal structure, mol-ecules are linked into chains running along the b axis by C-H⋯π inter-actions; adjacent chains are cross-linked via C-H⋯N hydrogen bonds and short S⋯N contacts [3.2694 (14) and 3.2953 (14) Å].

4-(4-Bromo-benzyl-ideneamino)-1-(diphenyl-amino-meth-yl)-3-[1-(4-isobutyl-phen-yl)eth-yl]-1H-1,2,4-triazole-5(4H)-thione.

In the title compound, C(34)H(34)BrN(5)S, the two phenyl rings of the diphenyl-amino-methyl group are inclined at an angle of 73.86 (8)° and they form dihedral angles of 74.04 (8) and 48.74 (8)° with the triazole ring. Intra-molecular C-H⋯S hydrogen bonds generate S(6) and S(5) ring motifs. The crystal structure is stabilized by weak C-H⋯π inter-actions.

3-[1-(4-Isobutyl-phen-yl)eth-yl]-6-(4-methyl-phen-yl)-1,2,4-triazolo[3,4-b][1,3,4]thia-diazole.

In the title compound, C(22)H(24)N(4)S, the methylphenyl and isobutylphenyl rings are inclined at an angle of 79.98 (1)° and they form dihedral angles of 4.59 (1) and 75.47 (1)°, respectively, with the triazolothia-diazole unit. An intra-molecular C-H⋯S hydrogen bond generates an S(5) ring motif. The crystal structure is stabilized by inter-molecular C-H⋯N hydrogen bonds and weak C-H⋯π and π-π inter-actions [centroid-centroid distances between the thia-diazole ring and a symmetry-related phenyl ring and between the triazole ring and the phenyl ring range from 3.5680 (8) to 3.7313 (8) Å].

4-[(E)-2,6-Dichloro-benzyl-ideneamino]-3-{1-[4-(2-methyl-prop-yl)phen-yl]eth-yl}-1H-1,2,4-triazole-5(4H)-thione.

In the title Schiff base compound, C(21)H(22)Cl(2)N(4)S, the triazole ring makes dihedral angles of 2.15 (11) and 87.48 (11)° with the 2,6-dichloro-phenyl and methyl-propyl-phenyl rings, respectively. Weak intra-molecular C-H⋯S and C-H⋯Cl inter-actions generate S(6) and S(5) ring motifs, respectively. In the crystal structure, centrosymmetrically related mol-ecules are linked into dimers by N-H⋯S hydrogen bonds. These dimers are arranged into sheets parallel to the ab plane and are stacked along the c axis. C-H⋯π inter-actions involving the methyl-propyl-phenyl ring and π-π inter-actions involving the dichloro-phenyl ring [centroid-centroid distance = 3.5865 (3) Å] are also observed.

4-[(E)-4-Bromo-benzyl-ideneamino]-3-methyl-1H-1,2,4-triazole-5(4H)-thione.

In the title mol-ecule, C(10)H(9)BrN(4)S, the dihedral angle between the triazole and benzene rings is 12.32 (19)°. An intra-molecular C-H⋯S hydrogen bond generates an S(6) ring motif. In the crystal packing, centrosymmetrically related mol-ecules are linked into a dimer by N-H⋯S hydrogen bonds, and the dimers are linked into a chain running along [11] by Br⋯N short contacts [3.187 (3) Å]. The crystal packing is further strengthened by π-π inter-actions involving the triazole ring [centroid-centroid distance = 3.322 (2) Å].

4-[(E)-2-Furylmethyl-eneamino]-3-phenyl-1H-1,2,4-triazole-5(4H)-thione.

In the title mol-ecule, C(13)H(10)N(4)OS, the triazole ring makes dihedral angles of 16.14 (9) and 58.51 (11)°, respectively, with the phenyl and furan rings. Intra-molecular C-H⋯N hydrogen bonds generate S(5) and S(6) ring motifs. In the crystal structure, centrosymmetrically related mol-ecules are linked via N-H⋯S hydrogen bonds to form dimeric pairs, which are inter-linked via C-H⋯O and C-H⋯π inter-actions.