General information
All commercially available starting materials were used without further purification. Melting points (mp) were determined by a Buchi B-545 apparatus and were uncorrected. 1H NMR and 13C NMR spectra were recorded using a Mercury-Plus 400 spectrometer in CDCl3 or DMSO-d6 solution and chemical shifts (δ) were expressed as parts per million (ppm) using tetramethylsilane as an internal reference. High-resolution mass spectra (HRMS) were carried out with an Agilent QTOF 6540 mass spectrometer. N-substituted acetoacetamides were synthesized according to the procedures reported by Armaghan [27].
Procedure for the preparation of 2-amino-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide derivatives 5a–v
To a mixture of appropriate aldehyde (0.3 mmol), 1H-1,2,4-triazole-3,5-diamine (0.3 mmol), N-substituted acetoacetamides (0.3 mmol) in DMF (5 mL) was added to p-toluenesulfonic acid (0.015 mmol), and the resulting solution was stirred for 16 h at 90°C. After cooling, the reaction mixtures was treated with saturated sodium bicarbonate solution (30 mL), extracted with EtOAc (3 × 20 mL), dried over anhydrous MgSO4, and evaporated in vacuo to give a precipitate, which was purified by silica gel column chromatography to provide the target compounds 5a–v in yields of 43–66%.
2-amino-5-methyl-N-(p-tolyl)-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5a). Yield, 58%; mp: 293.5-295.1°C; 1H NMR (400 MHz, DMSO-d6)d: 2.24 (s, 3H, CH3), 2.56 (s, 3H, CH3), 3.68 (s, 3H, CH3O), 3.69 (s, 6H, 2×CH3O), 6.44 (s, 2H, NH2), 7.05 (s, 2H, ArH), 7.10 (d, J = 8.0 Hz, 2H, ArH), 7.36 (d, J = 8.4 Hz, 2H, ArH), 10.39 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 172.84, 168.25, 163.54, 159.55, 157.64, 147.22, 144.11, 141.06, 138.37, 134.37, 129.54, 124.49, 124.01, 112.30, 65.23, 61.18, 27.79, 25.61. HRMS (ESI) m/z: calcd for C23H24N6O4 (M+H+) 449.1932 found 449.1931.
2-amino-N-(3-methoxyphenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5b),Yield: 49%; mp: 226.1-227.5°C; 1H NMR (400 MHz, DMSO-d6) d: 2.69 (s,3H, CH3), 3.67 (s, 3H, CH3O), 3.71 (s, 6H, 2×CH3O), 3.72 (s, 3H, CH3O), 6.60 (s, 2H, NH2), 6.70 (dd, J1 = 1.6 Hz, J2 = 8.0 Hz, 1H, ArH), 7.10 (s, 3H, ArH), 7.24 (s, 2H, ArH), 10.60 (s, 1H, NH).13C NMR (100 MHz, DMSO-d6) δ: 168.13, 163.78, 159.92, 158.75, 154.82, 152.91, 142.51, 139.93, 139.37, 130.11, 124.75, 119.18, 112.02, 109.92, 107.54, 105.59, 60.47, 56.41, 55.41, 23.05. HRMS (ESI) m/z: calcd for C23H24N6O5 (M+H+) 465.1881 found 465.1879.
2-amino-N-(4-methoxyphenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5c). Yield, 50%; mp: 290.5-291.3°C; 1H NMR (400 MHz, DMSO-d6)d: 2.69 (s, 3H, CH3), 3.69 (s, 3H,CH3O), 3.71 (s, 6H, 2×CH3O), 3.73 (s, 3H, CH3O), 6.59 (s, 2H, NH2), 6.91 (d, J = 8.8 Hz, 2H, ArH), 7.12 (s, 2H, ArH), 7.47 (d, J = 8.8 Hz, 2H, ArH),10.47 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 13C NMR (101 MHz, DMSO) δ 168.45, 163.82, 156.44, 156.27, 154.13, 152.97, 143.62, 139.12, 133.62, 132.06, 121.27, 118.41, 114.41, 106.27, 60.50, 56.18, 55.62, 15.50. HRMS (ESI) m/z: calcd for C23H24N6O5 (M+H+) 465.1881 found 465.1877.
2-amino-N-(3,4-dimethylphenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5d). Yield, 55%; mp: 308.1-309.2°C; 1H NMR (400 MHz, DMSO-d6) d: 2.16 (s, 6H, 2×CH3), 2.55 (s, 3H, CH3), 3.68 (s, 3H, CH3O),3.70 (s, 6H, 2×CH3O), 6.43 (s, 2H, NH2), 7.06 (s, 3H, ArH), 7.17 (d, J = 6.4 Hz, 1H, ArH), 7.27 (s, 1H, ArH), 10.40 (s,1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.04, 163.48, 158.80, 154.78, 152.88, 142.43, 139.31, 136.89, 136.57, 132.42, 130.03, 124.84, 120.97, 119.37, 117.35, 107.56, 60.47, 56.42, 23.02, 19.96, 19.21. HRMS (ESI) m/z: calcd for C24H26N6O4 (M+H+) 463.2089 found 463.2086.
2-amino-N-(3,4-dimethoxyphenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5e). Yield, 61%; mp: 281.0-282.3°C; 1H NMR (400 MHz, DMSO-d6) d: 2.57 (s, 3H, CH3), 3.68 (s, 6H, 2×CH3O), 3.71 (s, 9H, 3×CH3O), 6.45 (s, 2H, NH2), 6.88 (d, J = 8.4 Hz, 1H, ArH), 6.97 (dd, J1 = 2.0 Hz, J2 = 8.4 Hz, 1H, ArH), 7.06 (s, 2H, ArH), 7.10 (d, J = 2.0 Hz, 1H, ArH), 10.31 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.09, 163.32, 158.84, 154.80, 152.90, 148.98, 145.97, 142.49, 139.35, 132.28, 124.82, 119.27, 112.48, 111.97, 107.57, 104.84, 60.49, 56.43, 56.14, 55.73, 23.07. HRMS (ESI) m/z: calcd for C24H26N6O6 (M+H+) 495.1987 found 495.1984.
2-amino-N-mesityl-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5f). Yield, 52%; mp: 303.1-304.5°C; 1H NMR (400 MHz, DMSO-d6)d: 1.81 (s, 6H, 2×CH3), 2.19 (s, 3H, CH3), 2.79 (s, 3H, CH3), 3.73 (s, 3H, CH3O), 3.75 (s, 6H, 2×CH3O), 6.57 (s, 2H, NH2), 6.82 (s, 2H, ArH), 7.04 (s, 2H, ArH), 9.59 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.36, 164.09, 157.43, 154.01, 153.08, 143.56, 139.29, 136.18, 134.92, 134.21, 131.66, 128.93, 118.82, 107.17, 60.48, 56.39, 20.77, 18.11, 15.61. HRMS (ESI) m/z: calcd for C25H28N6O4 (M+H+) 477.2245 found 477.2240.
2-amino-N-(4-chlorophenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5g). Yield, 57%; mp: 289.3-291.5°C; 1H NMR (400 MHz, DMSO-d6) d: 2.57 (s, 3H, CH3), 3.67 (s, 3H, CH3O),3.69 (s, 6H, 2×CH3O), 6.47 (s, 2H, NH2), 7.04 (s, 2H, ArH), 7.37 (d, J =8.8 Hz, 2H, ArH), 7.51 (d, J = 8.8 Hz, 2H, ArH), 10.61 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.17, 163.88, 158.71, 154.84, 152.92, 142.59, 139.40, 137.73, 129.24, 128.17, 124.69, 121.18, 118.90, 107.50, 60.48, 56.44, 23.06. HRMS (ESI) m/z: calcd for C22H21ClN6O4 (M+H+) 469.1386 found 469.1377.
2-amino-5-methyl-N-(3-nitrophenyl)-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5h). Yield: 45%; mp: 329.5–330.9°C; 1H NMR (400 MHz, DMSO-d6) d: 2.72 (s, 3H, CH3), 3.65 (s, 3H, CH3O), 3.70 (s, 6H, 2×CH3O), 6.64 (s, 2H, NH2), 7.07 (s, 2H, ArH), 7.64 (t, J = 7.6 Hz, 1H, ArH), 7.83 (d, J = 7.2 Hz, 1H, ArH), 7.98 (d, J = 7.2 Hz, 1H, ArH), 8.59 (s, 1H, ArH), 11.07 (s, 1H,NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.56, 165.11, 156.61, 154.23, 153.03, 148.36, 143.92, 139.90, 139.18, 133.49, 130.91, 125.72, 119.23, 117.66, 113.79, 106.24, 60.48, 56.20, 15.53. HRMS (ESI) m/z: calcd for C22H21N7O6 (M+H+) 480.1626 found 480.1623.
2-amino-N-(4-fluorophenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5i).Yield, 57%; mp: 311.2-312.9°C; 1H NMR (400 MHz,DMSO-d6) δ: 2.57 (s, 3H, CH3), 3.68 (s, 3H, CH3O), 3.69 (s, 6H, 2×CH3O), 6.46 (s, 2H, NH2), 7.05 (s, 2H, ArH), 7.15 (t, J = 8.8 Hz, 2H, ArH), 7.48 (d, J = 4.8 Hz, 1H, ArH), 7.50 (d, J = 5.2Hz, 1H, ArH), 10.52 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.14, 163.67, 158.76, 154.83, 152.91, 142.55, 139.39, 135.19, 124.74, 121.56, 118.99, 116.05, 115.82, 107.53, 60.49, 56.44, 23.06. HRMS (ESI) m/z: calcd for C22H21FN6O4 (M+H+) 453.1681 found 453.1677.
2-amino-5-methyl-N-(4-nitrophenyl)-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5j). Yield, 43%;mp: 319.9-320.8°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.71 (s, 3H, CH3), 3.65 (s, 3H, CH3O), 3.70 (s, 6H, 2×CH3O), 6.64 (s, 2H, NH2), 7.05 (s, 2H, ArH), 7.81 (d, J= 9.2 Hz,2H, ArH), 8.25 (d, J= 9.2 Hz,2H, ArH), 11.18 (s, 1H, NH).13C NMR (100 MHz, DMSO-d6) δ: 168.57, 165.26, 156.62, 154.23, 153.03, 144.82, 143.92, 143.35, 139.16, 133.44, 125.53, 119.52, 117.63, 106.19, 60.49, 56.23, 15.54. HRMS (ESI) m/z: calcd for C22H21N7O6 (M+H+) 480.1626 found 480.1618.
2-amino-N-(4-bromophenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5k).Yield, 54%; mp: 280.1-284.3°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.69 (s, 3H, CH3), 3.67 (s, 3H, CH3O), 3.70 (s, 6H, 2×CH3O), 6.62 (s, 2H, NH2), 7.08 (s, 2H, ArH), 7.53 (s, 4H, ArH), 10.74 (s, 1H, NH).13C NMR (100 MHz, DMSO-d6) δ: 168.51, 164.50, 156.47, 154.17, 153.00, 143.73, 139.15, 138.26, 133.51, 132.18, 121.60, 118.05, 116.31, 106.22, 60.50, 56.20, 15.51. HRMS (ESI) m/z: calcd for C22H21BrN6O4 (M+H+) 513.0881 found 513.0870.
2-amino-N-(3-hydroxy-4-methoxyphenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5l).Yield, 56%; mp: 249.7-250.3°C;1H NMR (400 MHz, DMSO-d6) δ: 2.68 (s, 3H, CH3), 3.69 (s, 3H, CH3O), 3.72 (s, 9H, 3×CH3O), 6.58 (s, 2H, NH2), 6.85 (d, J = 8.4 Hz, 1H, ArH), 6.92 (d, J = 8.0 Hz, 1H, ArH), 7.12 (s, 2H, ArH), 7.15 (s, 1H,ArH), 9.12 (s, 1H, OH), 10.36 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.43, 163.69, 156.38, 154.11, 152.97, 146.90, 144.88, 143.55, 139.13, 133.60, 132.50, 118.54, 112.89, 110.52, 108.15, 106.26, 60.50, 56.28, 56.19, 15.48. HRMS (ESI) m/z: calcd for C23H24N6O6 (M+H+) 481.1830 found 481.1823.
2-amino-N-(4-methoxy-3-nitrophenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5m). Yield, 47%; mp: 286.1-288.2°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.51 (s, 3H, CH3), 3.67 (s, 3H, CH3O), 3.72 (s,6H,2×CH3O),3.90 (s, 3H, CH3O), 6.63 (s, 2H, NH2), 7.07 (s, 2H, ArH), 7.37 (d, J = 8.8 Hz, 1H, ArH), 7.67 (d, J = 7.6 Hz, 1H, ArH), 8.22 (s, 1H, ArH), 10.82 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.52, 164.56, 156.55, 154.20, 153.02, 149.12, 143.86, 139.17, 138.79, 133.52, 131.64, 125.89, 117.75, 116.01, 115.52, 106.23, 60.50, 57.23, 56.21, 15.52. HRMS (ESI) m/z: calcd for C23H23N7O7 (M+H+) 510.1732 found 510.1724.
2-amino-N-(3-amino-4-methoxyphenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5n).Yield, 53%; mp: 240.1-241.1°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.67 (s, 3H, CH3), 3.69 (s, 3H, CH3O),3.72 (s, 9H, 3×CH3O), 4.81 (s,2H, NH2), 6.56 (s, 2H, NH2), 6.71 (s, 2H, ArH), 6.97 (s, 1H, ArH), 7.13 (s, 2H, ArH), 10.25 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.40, 163.50, 156.31, 154.09, 152.96, 143.60, 143.45, 139.11, 138.18, 133.63, 132.56, 118.74, 110.90, 107.54, 106.26, 106.02, 60.50, 56.21, 55.89, 15.46. HRMS (ESI) m/z: calcd for C23H25N7O5 (M+H+) 480.1990 found 480.1986.
2-amino-N-(3-aminophenyl)-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5o). Yield, 63%; mp: 272.1-273.8°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.56 (s, 3H, CH3), 3.70 (s, 3H, CH3O),3.71 (s, 6H, 2×CH3O), 5.11 (s, 2H, NH2), 6.28 (d, J = 7.6 Hz, 1H, ArH), 6.42 (s, 2H, NH2), 6.53 (d, J = 7.6 Hz, 1H, ArH), 6.88 (s, 1H, ArH), 6.91 (d, J = 8.0 Hz, 1H, ArH),7.06 (s, 2H, ArH),10.19 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.02, 163.35, 158.75, 154.77, 152.89, 149.55, 142.32, 139.44, 139.35, 129.41, 124.80, 119.54, 110.46, 107.56, 107.43, 105.28, 60.49, 56.43, 23.00. HRMS (ESI) m/z: calcd for C22H23N7O4 (M+H+) 450.1885 found 450.1886.
2-amino-5-methyl-N-phenyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5p). Yield, 51%; mp: 305.1-306.5°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.58 (s, 3H, CH3), 3.67 (s, 3H, CH3O), 3.69 (s, 6H, 2×CH3O), 6.45 (s, 2H, NH2), 7.06 (s, 2H, ArH), 7.10 (d, J = 7.2 Hz, 1H, ArH), 7.30 (t, J = 8.0 Hz, 2H, ArH), 7.48 (d, J = 7.6 Hz, 2H, ArH), 10.47 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.12, 163.74, 158.77, 154.82, 152.90, 142.51, 139.37, 138.79, 129.27, 124.77, 124.56, 119.71, 119.18, 107.55, 60.47, 56.42, 23.05. HRMS (ESI) m/z: calcd for C22H22N6O4 (M+H+) 435.1776 found 435.1784.
2-amino-N-benzyl-5-methyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5q).Yield, 66%; mp: 230.1-231.5°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.60 (s, 3H, CH3), 3.74 (s, 6H, 2×CH3O),3.75 (s, 3H, CH3O), 4.36 (d, J = 5.6 Hz, 2H, CH2), 6.53 (s, 2H, NH2), 7.04 (t,J = 3.6 Hz, 2H, ArH), 7.07 (s, 2H, ArH), 7.22 (d, J = 2.4 Hz, 2H, ArH), 7.23 (s, 1H, NH), 8.96 (t, J = 5.6 Hz, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.31, 165.92, 156.64, 154.07, 153.01, 143.45, 139.22, 138.70, 133.76, 128.62, 127.59, 127.34, 118.26, 106.49, 60.57, 56.25, 43.18, 15.32. HRMS (ESI) m/z: calcd for C23H24N6O4 (M+H+) 449.1932 found 449.1930.
2-amino-5-methyl-N-phenethyl-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5r). Yield, 52%; mp: 252.1-253.5°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.47 (s, 3H, CH3), 2.61 (t, J = 7.2 Hz, 2H, CH2), 3.39 (d, J = 6.0 Hz, 2H, CH2), 3.71 (s, 3H, CH3O), 3.83 (s, 6H, 2×CH3O), 6.51 (s, 2H, NH2), 7.05 (d, J = 7.2 Hz, 2H, ArH), 7.11 (s, 2H, ArH), 7.20 (s, 1H, NH), 7.24 (t, J = 7.2 Hz, 2H, ArH), 8.52 (t, J = 5.6 Hz, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.28, 165.86, 156.44, 154.05, 152.99, 143.40, 139.43, 139.22, 133.77, 128.95, 128.68, 126.56, 118.43, 106.50, 60.51, 56.34, 40.96, 34.99, 15.19. HRMS (ESI) m/z: calcd for C24H26N6O4 (M+H+) 463.2089 found 463.2084.
2-amino-5-methyl-N-(thiazol-2-yl)-7-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5s). Yield, 47%; mp: 289.1-291.2°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.51 (s, 3H, CH3), 3.67 (s, 3H, CH3O), 3.69 (s, 6H, 2×CH3O), 6.51 (s,2H, NH2), 7.01 (s, 2H, ArH), 7.29 (d, J = 3.6 Hz, 1H, ArH), 7.48 (d, J= 3.6 Hz, 1H, ArH), 12.62 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.22, 164.01, 158.61, 157.67, 155.02, 152.85, 142.83, 139.52, 138.34, 124.42, 117.11, 114.70, 107.56, 60.53, 56.37, 23.10. HRMS (ESI) m/z: calcd for C19H19N7O4S (M+H+) 442.1292 found 442.1283.
2-amino-5-methyl-7-phenyl-N-(3,4,5-trimethoxyphenyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5t). Yield, 48%; mp: 293.2-295.1°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.70 (s, 3H, CH3), 3.67 (s, 3H, CH3O), 3.72 (s, 6H, 2×CH3O), 6.61 (s, 2H, NH2), 6.83 (s, 2H, ArH), 7.46 (s, 2H, ArH), 7.48 (s, 1H, ArH),7.78 (d, J = 5.6 Hz, 2H, ArH), 10.42 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.50, 163.93, 157.09, 154.28, 153.19, 143.75, 138.41, 134.85, 134.62, 130.03, 128.75, 118.41, 97.91, 60.49, 56.16, 15.58. HRMS (ESI) m/z: calcd for C22H22N6O4 (M+H+) 435.1776 found 435.1751.
2-amino-N-(4-fluorophenyl)-5-methyl-7-phenyl-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5u). Yield, 46%; mp: 285.9-287.1°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.71 (s, 3H, CH3), 6.62 (s, 2H, NH2), 7.15 (t, J = 8.8 Hz, 2H, ArH), 7.44-7.50 (m, 5H, ArH), 7.76 (d, J = 4.0 Hz, 2H, ArH), 10.53 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.51, 164.03, 160.17, 157.77, 157.15, 154.30, 143.80, 138.38, 135.08, 130.01, 128.71, 121.99, 118.21, 115.99, 15.52. HRMS (ESI) m/z: calcd for C19H15FN6O (M+H+) 363.1364 found 363.1363.
2-amino-5-methyl-7-phenyl-N-(p-tolyl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide (5v).Yield, 60%; mp: 266.1-267.8°C; 1H NMR (400 MHz, DMSO-d6) δ: 2.24 (s, 3H, CH3), 2.69 (s, 3H, CH3), 6.60 (s, 2H, NH2), 7.11 (s, 2H, ArH), 7.35 (s, 2H, ArH), 7.43 (s, 3H, ArH), 7.76 (s, 2H, ArH), 10.38 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6) δ: 168.46, 163.87, 157.13, 154.27, 143.72, 138.41, 136.23, 133.71, 129.97, 129.58, 128.67, 120.11, 118.47, 20.86, 15.49. HRMS (ESI) m/z: calcd for C20H18N6O (M+H+) 359.1615 found 359.1615.
Antiproliferative activity
The cancer cell growth inhibition activity of compounds 5a–v were evaluated in vitro toward a panel of three different human cancer cell lines, including T47D, A549, and Panc-1 using the standard MTT assay. T47D and A549 cells were cultured in RPMI-1640, and Panc-1 was cultured with DMEM medium supplemented with 10% FBS. Tested samples were dissolved in dimethyl sulfoxide (DMSO) at 100 mM and compound 5l was diluted into a series of concentrations with the medium. Exponentially growing cells were then seeded into 96-well plates (2×103 cells/well) and incubated at 37 °C for 48 h. The medium was changed, and cells grew with the tested samples, including 0.1% DMSO as a negative control. Subsequently, 10 μL of MTT solution (5 mg/mL) was added into each well, and the plates were incubated for 4 h at 37°C. Finally, absorbance at 570 nm (Abs) of the suspension was obtained with a microplate reader, and inhibition percentage was measured using the following formula: % inhibition = (Abscontrol-Abscompound)/Abscontrol×100%. IC50 values of compound 5l was calculated through the prism statistical package (GraphPad Software, San Diego, CA, U.S.A.).