Materials
All reagents and solvents used are commercially available. Reactions were monitored by thin layer chromatography (TLC) using silica gel F254 aluminum sheets (Merck). Melting points were measured on an Electrothermal apparatus. Infra-red spectra were recorded (KBr discs) with a Galaxy Series FT-IR 5000 spectrometer. The 1H NMR and 13C NMR spectra were recorded with a Bruker Avance 300 MHz spectrometer with DMSO-d6 and CDCl3 as the solvent and tetramethylsilane as an internal standard. Microanalyses were performed by the Elemental Analyzer (Elemental, Vario EL III) at the Arak University. The microbial strains are identified strains and were obtained from the Pasteur Institute of Iran. The bacterial strains studied are Staphylococcus aureus (RTCC, 1885), and Escherichia Coli (ATCC, 35922).
General procedure for the synthesis of compounds 6-8
In a typical experimental procedure (
34-
36), benzaldehyde 1 (1 mmol), malononitrile 2 (1 mmol), dimedone 3, resorcinol 4 or 2-naphthol 5 (1 mmol) were mixed in solvent and triethylamine (2-3 drops) as a catalyst was added. The reaction mixture was refluxed for 2-4 h. After the completion of the reaction, it was filtered and recrystallized from ethanol to afford the pure product 6-8.
2-Amino-7,7-dimethyl-5-oxo-4-phenyl-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (6): Yield: 85% m.p 227-229 °C. IR (KBr): 3395, 3326, 2199, 1682 cm-1. Elemental analysis. Found, %: C 73.52; H 6.28; N 9.36, C18H18N2O2, Calculated, %: C 73.45; H 6.16; N 9.52.
2-Amino-7-hydroxy-4-phenyl-4H-chromene-3-carbonitrile (7): Yield: 78%, m.p 234-235 °C. IR (KBr): 3499, 3427, 3331, 2193 cm-1. Elemental analysis. Found, %: C 72.48; H 4.61; N 10.7. C16H12N2O2, Calculated, %: C 72.72; H 4.58; N 10.60.
3-Amino-1-phenyl-1H-benzo[f]chromene-2-carbonitrile (8): Yield: 80%, m.p 279-280 °C. IR (KBr): 3435, 3338, 2183 cm-1. Elemental analysis. Found. %: C 80.27; H 4.50; N 9.74. Calculated, %: C20H14N2O, C 80.52; H 4.73; N 9.39.
General procedure for the synthesis of compounds 9-11
To a solution of 2-amino-3-carbonitrile 6-8 (1 mmol) in 1,4-dioxane (20 mL) was added triethylorthoformate (2 mmol) and acetic anhydride (2 mmol). The reaction mixture was heated under reflux condition for 2-4 h. After the completion of the reaction, the solvent was removed and the precipitate was recrystallized from ethanol to afford the pure product 9-11.
Ethyl N-3-cyano-7,7-dimethyl-5-oxo-4-phenyl-5,6,7,8-tetrahydro-4H-chromen-2-ylformimidate (9): reaction time: 2h, Yield 85%, m.p 178-180 °C. IR (KBr): 2206, 1674 cm-1. 1H N.M.R. (CDCl3) (ppm) (J, Hz): 1.11 (3H, s, CH3), 1.19 (3H, s, CH3), 1.28 (3H, t, CH3, J=6.6), 2.25 (2H, s, CH2), 2.47 (2H, s, CH2), 4.37 (2H, q, J=6.6, CH2,) 4.54 (1H, s, Hpyran), 7.21-7.35 (5H, m, Haromatic), 8.25 (1H, s, Himine). Elemental analysis. Found. %: C 72.27; H 6.14; N 7.89. C21H22N2O, Calculated, %: C 71.98; H 6.33; N 7.99.
Ethyl N-3-cyano-7-hydroxy-4-phenyl-4H-chromen-2-ylformimidate (10): reaction time: 3h, Yield 80%, m.p 166-168 °C. IR (KBr): 3110, 2224 cm-1. 1H N.M.R. (CDCl3) (ppm) (J, Hz): 1.34 (3H, t, J=5.6, CH3,), 4.39 (2H, q, J=5.6, CH2,), 4.83 (1H, s, Hpyran), 6.79-7.37 (8H, m, Haromatic and 1H, OH), 8.39 (1H, s, Himine). 13C N.M.R. (CDCl3) (ppm): 21.1, 42.5, 64.2, 81.2, 110.2, 119.4, 119.7, 127.3, 127.7, 127.9, 128.1, 128.2, 129.0, 143.3, 157.0, 159.6, 169.1. Elemental analysis. Found, %: C 71.01; H 5.21; N 8.51. C19H16N2O3, Calculated, %: C 71.24; H 5.03; N 8.74.
Ethyl N-2-cyano-1-phenyl-1H-benzo[f]chromen-3-ylformimidate (11): reaction time: 4 h, Yield 75%, m.p 224-226 °C. IR (KBr): 2224 cm-1. 1H N.M.R. (CDCl3) (ppm) (J, Hz): 1.35 (3H, t, J=7.1, CH3), 4.40 (2H, q, J=7.1, CH2,), 5.30 (1H, s, Hpyran), 7.21-7.86 (11H, m, Haromatic), 8.45 (1H, s, Himine). 13C N.M.R. (CDCl3) (ppm): 13.9, 40.8, 64.2, 82.2, 113.9, 116.8, 118.3, 123.7, 125.2, 127.4, 127.7, 128.6, 129.1, 129.9, 130.7, 131.5, 143.1, 147.6, 156.6, 159.5. 168.2. Elemental analysis. Found. %: C 77.76; H 5.02; N 9.021. C23H18N2O2, Calculated, %: C 77.95; H 5.12; N 9.03.
General procedure for the synthesis of compounds 12-20
A mixture of imine 9-11 (1 mmol) and ammonia or primary amine (1 mmol) in ethanol or 1,4-dioxane (15 mL) was refluxed for the indicated time (
Table 1). After completion of the reaction, the solid material was separated and recrystallized from ethanol to give compounds 12-20.
4-Imino-8,8-dimethyl-5-phenyl-5,7,8,9-tetrahydro-3H-chromeno[2,3-d]pyrimidin- 6(4H)-one (12): IR (KBr): 3308-3464, 1691 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 0.90-1.10 (6H, s, 2CH3), 2.14 (2H, s, CH2), 2.35 (2H, s, CH2), 5.58 (1H, s, Hpyran), 6.90-7.31 (6H, m, Haromatic), 7.81 (1H, s, NH), 8.07 (1H, s, HIimine), 11.61 (1H, s, NH). 13C N.M.R. (DMSO-d6) (ppm): 26.9, 28.5, 43.6, 50.5, 56.5, 127.0, 127.9, 128.5, 140.9, 143.5, 147.7, 156.7, 163.1, 164.4, 165.1, 193.8. Elemental analysis. Found. %: C 71.27; H 5.70; N 13.28. C19H19N3O2, Calculated, %: C 71.01; H 5.96; N 13.08.
4-Imino-8,8-dimethyl-3-(3-nitrophenyl)-5-phenyl-5,7,8,9-tetrahydro-3H-chromeno[2,3-d]pyrimidin-6(4H)-one (13): IR (KBr): 3421, 1684, 1645 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 1.00 (3H, s, CH3), 1.08 (3H, s, CH3), 2.13 (2H, s, CH2), 2.64 (2H, s, CH2), 4.40 (1H, s, Hpyran), 7.21-9.00 (11H, m, Haromatic, Himine, NH). 13C N.M.R. (DMSO-d6) (ppm): 25.1, 25.4, 27.3, 29.8, 31.2, 52.6, 101.2, 123.7, 124.9, 126.1, 128.7, 129.9, 131.2, 133.7, 135.1, 139.5, 142.1, 143.9, 145.1, 148.7, 153.2, 159.9, 173.4. Elemental analysis. Found. %: C 67.62; H 4.91; N 12.50. C25H22N4O4, Calculated, %: C 67.86; H 5.01; N 12.66.
4-Imino-5-phenyl-4,5-dihydro-3H-chromeno[2,3-d]pyrimidin-8-ol (14): IR (KBr): 3462, 3310, 3094 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 5.15 (1H, s, Hpyran), 6.51-7.25 (10H, m, Haromatic, NH), 8.09 (1H, s, Himine), 9.65 (1H, s, OH). 13C N.M.R. (DMSO-d6) (ppm): 37.9, 96.6, 103.5, 112.8, 115.9, 127.1, 127.7, 129.0, 130.2, 145.4, 150.5, 156.9, 157.7, 162.9, 163.1. Elemental analysis. Found, %: C 70.23; H 4.63; N 14.59. C17H13N3O2, Calculated, %: C 70.09; H 4.50; N 14.42.
3-(2-Chlorophenyl)-4-imino-5-phenyl-4,5-dihydro-3H-chromeno[2,3-d]pyrimidin-8-ol (15): IR (KBr): 3393, 3157, 1635 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 5.48 (1H, s, Hpyran), 6.56-8.26 (14H, m, Haromatic, NH, Himine), 9.79 (1H, s, OH). 13C N.M.R. (DMSO-d6) (ppm): 37.7, 98.9, 103.5, 113.1, 115.3, 126.8, 127.5, 127.9, 128.6, 129.3, 129.9, 130.4, 136.2, 144.8, 150.1, 156.7, 157.8, 159.82, 159.83, 163.3. Elemental analysis. Found, %: C 68.89; H 4.21; Cl 8.61; N 10.29. C23H16ClN3O2, Calculated, %: C 68.74; H 4.01; Cl 8.82; N 10.46.
4-Imino-3-(3-nitrophenyl)-5-phenyl-4,5-dihydro-3H-chromeno[2,3-d]pyrimidin-8-ol (16): IR (KBr): 3402, 3142, 1612 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 5.74 (1H, s, Hpyran), 6.60-8.05 (12H, m, Haromatic), 8.60 (1H, s, Himine), 8.95 (1H, s, NH), 9.76 (1H, s, OH). 13C N.M.R. (DMSO-d6) (ppm): 37.2, 100.4, 103.7, 107.6, 113.3, 115.3, 117.6, 120.4, 127.3, 127.5, 129.3, 130.1, 130.2, 141.2, 145.3, 148.3, 150.3, 156.5, 158.0, 159.0, 163.6. Elemental analysis. Found, %: C 66.76; H 3.84; N 13.35. C23H16N4O4, Calculated, %: C 66.99; H 3.91; N 13.59.
4-Imino-5-phenyl-3-p-tolyl-4,5-dihydro-3H-chromeno[2,3-d]pyrimidin-8-ol (17): IR (KBr): 3427, 3092, 1635 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 2.24 (3H, s, CH3), 5.63 (1H, s, Hpyran), 6.56-7.41 (12H, m, Haromatic), 8.29 (1H, s, Himine), 8.31 (1H, s, NH), 9.71 (1H, s, OH). 13C N.M.R. (DMSO-d6) (ppm): 20.9, 37.2, 99.0, 103.5, 113.1, 115.5, 122.1, 127.3, 127.6, 129.2, 129.3, 130.2, 132.7, 137.2, 145.4, 150.3, 156.6, 157.8, 159.4, 163.1. Elemental analysis. Found. %: C 75.69; H 4.91; N 11.26. C24H19N3O2, Calculated, %: C 75.57; H 5.02; N 11.02.
3-(4-Ethylphenyl)-4-imino-5-phenyl-4,5-dihydro-3H-chromeno[2,3-d]pyrimidin-8-ol (18): IR (KBr): 3421, 3109, 1635 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 1.13 (3H, t, J=7.0, CH3), 2.49 (2H, q, J=7.0, CH2), 5.63 (1H, s, Hpyran), 6.03-7.42 (12H, m, Haromatic), 8.29 (1H, s, Himine), 8.35 (1H, s, NH), 9.76 (1H, s, OH). 13C N.M.R. (DMSO-d6) (ppm): 16.2, 28.0, 37.1, 99.0, 103.5, 113.1, 115.5, 122.1, 127.3, 127.5, 128.1, 129.2, 130.3, 137.3, 139.3, 145.4, 150.3, 156.6, 157.8, 159.4, 163.1. Elemental analysis. Found. %: C 75.79; H 5.41; N 10.51. C25H21N3O2, Calculated, %: C 75.93; H 5.35; N 10.63.
3-Benzyl-4-imino-5-phenyl-4,5-dihydro-3H-chromeno[2,3-d]pyrimidin-8-ol (19): IR (KBr): 3340, 3115 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 4.36 (1H, s, Hbenzyl), 4.78 (1H, s, Hpyran), 6.54-7.47 (13H, m, Haromatic), 7.79 (1H, s, NH), 8.51 (1H, s, Himine), 9.32 (1H, s, OH). 13C N.M.R. (DMSO-d6) (ppm): 42.9, 64.4, 121.2, 122.8, 123.7, 134.1, 136.5, 138.2, 140.5, 142.1, 144.3, 145.7, 148.3, 150.6, 152.1, 154.7, 156.7, 158.2, 159.6, 160.4. Elemental analysis. Found, %: C 75.48; H 5.28; N 10.90. C24H19N3O2, Calculated, %: C 75.57; H 5.02; N 11.02.
12-Phenyl-10H-benzo[f]chromeno[2,3-d]pyrimidine-11(12H)-imine (20): IR (KBr): 3437, 3317, 1647 cm-1. 1H N.M.R. (DMSO-d6) (ppm) (J, Hz): 6.06 (1H, s, Hpyran), 7.08-8.24 (14H, m, Haromatic, Himine, NH). 13C N.M.R. (DMSO-d6) (ppm): 34.7, 97.6, 118.1, 123.6, 125.3, 127.1, 127.5, 128.1, 128.9, 129.1, 129.8, 131.3, 144.2, 148.3, 156.8, 162.9. Elemental analysis. Found, %: C 77.64; H 4.50; N 12.99. C21H15N3O, Calculated, %: C 77.52; H 4.65; N 12.91.
Antibacterial activities
We used the agar disk diffusion method for this purpose. Each chemically synthesized materials (5 mg) was solved in DMSO as a solvent and 100 μL of known concentration of the test compounds was introduced onto the disks (7 mm) and then allowed to dry. Then the disk was introduced onto the upper layer of the medium with the bacteria. 100 μL of solvent (DMSO) was added to another disk and implanted as a negative control on each plate along with the standard drugs. The plates were incubated overnight at 37 °C. The inhibition zones were measured and compared with the standard drugs. The results are given in
Table 2. The inhibition zone numbers are the average of three times of dependent experiments.