Imidazo [1, 2-alpha] pyridine compound, preparation method and application in preparation of antibacterial drugs

Abstract

The invention discloses an imidazo [1, 2-alpha] pyridine compound, a preparation method thereof and application of the imidazo [1, 2-alpha] pyridine compound in preparation of antibacterial drugs, and belongs to the technical field of organic synthesis and application. The structural formula of the imidazo [1, 2-alpha] pyridine compound is shown in the specification. The method comprises the following steps: mixing an imidazo [1, 2-alpha] pyridine compound I, a benzotriazole compound II and g-C3N4 in a solvent, carrying out a reaction under the irradiation of a blue LED lamp under an air condition, filtering after the reaction is finished, desolventizing the filtrate, drying, and carrying out column chromatography separation to obtain the imidazo [1, 2-alpha] pyridine compound. The preparation method is simple, the raw material cost is low, the yield is high, and the prepared imidazo [1, 2-alpha] pyridine compound has bacteriostatic activity and can be applied to preparation of antibacterial drugs.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis and application, and particularly relates to an imidazo[1,2-a]pyridine compound, a preparation method and application thereof in preparation of antibacterial drugs. BACKGROUND

[0002] Imidazo[1,2-a]pyridine compounds are a kind of nitrogen-containing fused heterocyclic compounds mainly containing imidazole groups and pyridine groups, which have wide biological activity and chemical reactivity and have wide application value in the fields of medicine and chemistry. The imidazo[1,2-a]pyridine structure is also a good drug active fragment, and drugs designed based on the fragment often have the effects of anti-tumor, antibacterial and enzyme inhibition.

[0003] In 2013, Sun et al. realized the coupling reaction of imidazo[1,2-a]pyridine and sulfonamide under light conditions, but the reaction used an expensive metal catalyst, which significantly increased the experimental cost and was not environmentally friendly. In addition, the reaction system additionally used an oxidant NaClO, further increasing the experimental cost. In 2019, Yan et al. reported the reaction of imidazo[1,2-a]pyridine and alcohol compounds, and synthesized a series of hydroxyalkylated imidazo[1,2-a]pyridine compounds. The reaction needs to use an excess of an oxidant DTBP and an equivalent of hydrochloric acid as an additive. In 2016, Sun et al. reported the reaction of imidazo[1,2-a]pyridine and hydrazine formate compounds, but the reaction needs to use a metal Fe as a catalyst, an excess of (NH4)2S2O8 as an oxidant, and an organic solvent DMSO, which does not meet the requirements of green chemistry, and the range of substituents of the reaction substrate is limited.

[0004] Therefore, it is of great significance to develop a method for synthesizing imidazo[1,2-a]pyridine compounds with low cost and green environmental protection. SUMMARY

[0005] In view of the problems in the prior art, the application provides an imidazo[1,2-a]pyridine compound, a preparation method and application thereof in preparation of antibacterial drugs. The preparation method is simple in operation, low in raw material cost and high in yield, and the prepared imidazo[1,2-a]pyridine compound has antibacterial activity and can be applied to the preparation of antibacterial drugs.

[0006] The application is implemented through the following technical solutions. In a first aspect, the application provides an imidazo[1,2-a]pyridine compound, and the structure of the imidazo[1,2-a]pyridine compound is shown in the following formula III: ; R1 is one of H, alkyl, phenyl, methoxy, halogen; R 2 is one of H, alkyl, phenyl, methoxy, halogen; R 3 is one of H, alkyl, phenyl, methoxy, halogen, or forms a benzene ring with the benzene ring.

[0007] In the second aspect of the present application, a preparation method of the imidazo[1,2-a]pyridine compound is provided, characterized in that: imidazo[1,2-a]pyridine compound I, benzotriazole compound II and g-C3N4 are mixed in a solvent, and the reaction is carried out by irradiation under air condition using a blue LED lamp, after the reaction is completed, filtration is carried out, the filtrate is desolventized, dried, and column chromatography is carried out to obtain imidazo[1,2-a]pyridine compound III; the reaction formula is shown in the following formula: .

[0008] Further, the molar ratio of the imidazo[1,2-a]pyridine compound I and the benzotriazole compound II is 1:1.

[0009] Further, the molar ratio of the imidazo[1,2-a]pyridine compound I and g-C3N4 is 2:0.02-0.025.

[0010] Further, the solvent is a mixed solvent of acetone and water, or ethanol and water, and the volume ratio of acetone or ethanol to water is 1:6-8.

[0011] Further, the reaction progress is monitored by TLC until the raw material point disappears.

[0012] Further, the column chromatography separation method is silica gel column chromatography separation.

[0013] In the third aspect of the present application, the imidazo[1,2-a]pyridine compound is applied to preparation of an antibacterial preparation.

[0014] Compared with the prior art, the present application has the following beneficial effects: (1) The preparation method of the imidazo[1,2-a]pyridine compound disclosed in the present application is simple in operation, low in raw material cost, high in yield, green and environmentally friendly, and is conducive to further promotion. (2) The imidazo[1,2-a]pyridine compound prepared in the present application has significant bacteriostatic activity and has the prospect of being developed into an antibacterial drug. DETAILED DESCRIPTION

[0015] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. The experimental methods in the following examples, if not otherwise specified, are generally carried out according to the conventional conditions or according to the conditions suggested by the manufacturers.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The reagents or materials used in the present application can be purchased by conventional routes, and if no special description, the reagents or materials used in the present application are used according to the conventional manner in the art or according to the product instructions.

[0017] Example 1 100 mL three-necked flask was added imidazo[1,2-a]pyridine compound (2 mmol) as shown below, benzotriazole (2 mmol) compound, then added g-C3N4 (0.01 mol), 10 mL acetone / water (1:6), air condition blue LED light irradiation, stirring at room temperature, TLC monitoring raw material, until the raw material point disappeared to stop the reaction, the reaction liquid was filtered, the filtrate was desolventized, dried, and separated by silica gel column chromatography to obtain the target imidazo[1,2-a]pyridine compound A1 636.1 mg, yield 90%. 1 H NMR (500 MHz, CDCl3) δ: 7.96 (s, 1H), 7.55~7.47 (m, 3H), 7.29 (d, J=6.9 Hz, 1H), 7.25~7.20 (m, 3H), 6.90 (s, 1H), 6.65 (d, J=6.9 Hz, 1H), 2.45(s, 3H), 2.44 (s, 3H), 2.28 (s, 3H); 13 C NMR (126 MHz, CDCl3) δ: 145.0, 144.4,141.1, 139.9, 137.7, 134.9, 133.2, 131.8, 128.6, 127.0, 121.6, 119.7, 116.4,116.1, 112.0, 109.1, 21.4, 20.8, 20.4. HRMS (ESI) calcd for C 22 H 20 N5[M+H] ＋ 354.1711, found 354.1713; the reaction formula is as shown below: .

[0018] Example 2 100 mL three-necked flask was added imidazo[1,2-a]pyridine (2 mmol) compound, benzotriazole (2 mmol) compound as shown below, then g-C3N4 (0.02 mol) was added, 10 mL ethanol / water (1:6) was added, and the reaction was carried out under the irradiation of a blue LED lamp in air at room temperature. TLC was used to monitor the raw material until the raw material point disappeared. The reaction was stopped, the reaction solution was filtered, the filtrate was desolved, dried, and separated by silica gel column chromatography to obtain the target product imidazo[1,2-a]pyridine compound A2 598.5 mg, yield 92%. 1 H NMR (500 MHz, CDCl3) δ: 8.24 (d, J=1.7 Hz, 1H), 7.54 (s, 1H), 7.48 (d,J=2.1 Hz, 4H), 7.37 (d, J=3.3 Hz, 1H), 7.23 (s, 3H), 7.13 (s, 1H), 6.68 (s,1H), 2.45 (s, 3H); 13 C NMR (126 MHz,CDCl3) δ: 145.8, 144.5, 141.1, 138.0,134.1, 131.7, 129.2, 128.7, 127.0, 125.0, 121.6, 120.6, 116.3, 111.7, 109.8,21.4. HRMS (ESI) calcd for C 20 H 16 N5[M+H] ＋ 326.1398, found 326.1400;reaction formula as shown below: .

[0019] Example 3 100 mL three-necked flask was added imidazo[1,2-a]pyridine (2 mmol) compound, benzotriazole (2 mmol) compound as shown below, then g-C3N4 (0.021 mol) was added, 10 mL ethanol / water (1:8) was added, and the reaction was carried out under the irradiation of a blue LED lamp in air at room temperature. TLC was used to monitor the raw material until the raw material point disappeared. The reaction was stopped, the reaction solution was filtered, the filtrate was desolved, dried, and separated by silica gel column chromatography to obtain the target product imidazo[1,2-a]pyridine compound A3 624.5 mg, yield 96%. 1H NMR (500 MHz, CDCl3) δ: 8.23 ​​(d, J=6.3 Hz, 1H), 7.53 (s, 2H), 7.49~7.39 (m, 2H), 7.33 (d, J=5.3 Hz, 1H), 7.28~7.19 (m, 3H), 7.17~7.07 (m,2H), 6.79~6.67 (m, 1H), 2.76 (s, 3H); 13 C NMR (126 MHz, CDCl3) δ: 145.8,144.4, 140.9, 134.1, 131.8, 129.2, 128.7, 128.7, 128.1, 127.2, 125.3, 125.1,120.6, 120.4, 113.6, 112.5, 109.8, 16.7. HRMS (ESI) calcd for C 20 H 16 N5[M+H] ＋ 326.1398, found 326.1400; The reaction formula is shown below: .

[0020] Example 4 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolventized, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A4, 636.0 mg, with a yield of 92%. 1 H NMR (500 MHz, CDCl3) δ: 8.24 (d, J=7.3 Hz, 1H), 7.78 (s, 1H), 7.46 (d, J=7.3 Hz, 5H), 7.23 (d, J=7.2 Hz, 3H), 7.12 (d, J=7.5 Hz, 1H), 6.84 (d, J=7.1 Hz, 1H); 13C NMR (126 MHz, CDCl3) δ: 145.8, 143.8, 142.0, 133.9, 133.4,131.1, 130.2, 129.7, 129.5, 128.9, 127.1, 125.2, 122.9, 120.7, 116.9,C 19 H 13 N5Cl[M+H] ＋ 115.3, 112.5, 109.7. HRMS (ESI) calcd for 346.0851, found 346.0854; the reaction formula is shown below: .

[0021] Example 5 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolventized, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A5, 725.1 mg, with a yield of 97%. 1 H NMR (500 MHz, CDCl3) δ: 7.97 (s, 1H), 7.78 (d, J=1.1 Hz, 1H), 7.49 (dd, J=7.4, 1.8 Hz, 2H), 7.37 (d, J=7.2 Hz, 1H), 7.26 (d, J=11.4 Hz, 3H), 6.89 (s, 1H), 6.82 (dd, J= 7.2, 1.8 Hz, 1H), 2.44 (s, 3H), 2.29 (s, 3H); 13 CNMR (126 MHz, CDCl3) δ: 145.0, 143.7, 142.1, 140.2, 135.1, 133.3, 133.0,131.2, 129.0, 128.7, 127.1, 122.8, 119.8, 116.9, 115.2, 112.8, 109.0, 20.9,20.4. HRMS (ESI) calcd for C 21 H 17 N5Cl [M+H] ＋374.1165, found 374.1167; The reaction formula is shown below: .

[0022] Example 6 Add the following compounds to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Add 10 mL of acetone / water (1:6), irradiate with a blue LED lamp under air, stir at room temperature, monitor the starting material by TLC, and stop the reaction when the starting material spot disappears. Filter the reaction solution, remove solvent from the filtrate, dry, and separate by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A6, 638.8 mg, with a yield of 97%. 1 H NMR (500 MHz, CDCl3) δ: 8.32~8.19 (m, 1H), 7.78 (d, J=9.1 Hz, 1H), 7.57~7.44 (m, 5H), 7.38 (ddd, J=9.1, 6.8, 1.2 Hz, 1H), 7.19~7.09 (m, 1H), 6.99~6.89 (m, 2H), 6.86 (td, J=6.8, 1.0 Hz, 1H); 13 C NMR (126 MHz, CDCl3) δ:164.0, 162.0, 145.8, 144.0, 140.6, 133.9, 129.4, 128.9, 127.7, 126.8, 125.1,122.5, 120.7, 118.0, 115.9, 115.7, 113.7, 111.9, 109.6. HRMS (ESI) calcd forC 19 H 13 N5F [M+H] ＋ 330.1149, found 330.1149; The reaction formula is shown below: .

[0023] Example 7 Add the following compounds to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Add 10 mL of acetone / water (1:6), irradiate with a blue LED lamp under air, stir at room temperature, monitor the starting material by TLC, and stop the reaction when the starting material spot disappears. Filter the reaction solution, remove solvent from the filtrate, dry, and separate by silica gel column chromatography to obtain the target product imidazo[1,2-α]pyridine compound A7 677.5 mg, with a yield of 98%. 1 H NMR (500 MHz, CDCl3) δ: 8.26 (d, J=7.5 Hz, 1H), 7.79 (d, J=9.1 Hz, 1H), 7.50 (d, J=7.3 Hz, 3H), 7.46~7.38 (m, 3H), 7.21 (d, J=7.9 Hz, 2H), 7.13 (d, J=5.4 Hz, 1H), 6.90~ 6.84 (m, 1H); 13 C NMR (126 MHz, CDCl3) δ:145.8, 144.1, 140.3, 134.8, 133.9, 130.6, 130.0, 130.0, 129.2, 128.4, 126.9,125.2, 122.5, 120.8, 118.1, 113.8, 109.6. HRMS (ESI) calcd for C 19 H 13 N5Cl [M+H] ＋ 346.0852, found 346.0854; The reaction formula is shown below: .

[0024] Example 8 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolvated, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A8, 671.1 mg, with a yield of 86%. 1H NMR (500 MHz, CDCl3) δ: 8.26 (d, J=8.3 Hz, 1H), 7.79 (d, J=9.1 Hz, 1H), 7.60~7.47 (m, 4H), 7.43~7.33 (m, 4H), 7.13 (d, J=4.9 Hz, 1H), 6.92~6.83 (m, 1H); 13 C NMR (126 MHz, CDCl3) δ: 145.8, 144.1, 137.9, 133.9, 131.9,129.5, 128.6, 127.0, 125.2, 123.2, 122.5, 120.8, 118.1, 113.8, 109.6. HRMS(ESI) calcd for C 19 H 13 N5Br [M+H] ＋ 390.0346, found 390.0348; The reaction formula is shown below: .

[0025] Example 9 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolvated, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A9, 733.5 mg, with a yield of 94%. 1 H NMR (500 MHz, CDCl3) δ: 8.31~8.20 (m, 1H), 7.93 (s, 1H), 7.79 (d, J=9.1 Hz, 1H), 7.58~7.46 (m, 3H), 7.39 (dd, J=16.6, 8.3 Hz, 2H), 7.13 (d, J=7.2 Hz, 2H), 7.02 (t, J=7.9 Hz, 1H), 6.87 (t, J=6.7 Hz, 1H); 13C NMR (126MHz, CDCl3) δ: 145.8, 144.1, 139.8, 133.9, 133.7, 131.7, 130.2, 129.5, 127.0,125.2, 123.1, 122.7, 120.8, 118.1, 113.9, 112.5, 109.6. HRMS (ESI) calcd forC 19 H 13 N5Br [M+H] ＋ 390.0346, found 390.0348; The reaction formula is shown below: .

[0026] Example 10 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolvated, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A10, 617.7 mg, with a yield of 91%. 1 H NMR (500 MHz, CDCl3) δ: 8.24 (d, J=7.2 Hz, 1H), 7.57~7.44 (m, 3H), 7.36 (d, J=6.8 Hz, 3H), 7.13 (d, J=7.5 Hz, 1H), 7.03 (d, J=7.5 Hz, 2H), 6.66 (d, J=6.7 Hz, 1H), 2.45 (s, 3H), 2.27 (s, 3H); 13 C NMR (126 MHz, CDCl3)δ: 145.8, 144.5, 138.6, 137.8, 134.1, 130.0, 129.8, 129.20, 126.9, 125.0,121.6, 120.6, 117.3, 116.6, 116.2, 109.8, 21.5, 21.2. HRMS (ESI) calcd forC 21 H 18 N5[M+H] ＋ 340.1555, found 340.1556; The reaction formula is shown below: .

[0027] Example 11 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolventized, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A11, 640.4 mg, with a yield of 89%. 1 H NMR (500 MHz, CDCl3) δ: 8.25 (dd, J=5.5, 3.7 Hz, 1H), 7.50 (dd, J=13.0, 9.2 Hz, 3H), 7.39 (dd, J=17.0, 7.8 Hz, 3H), 7.20 (d, J=8.5 Hz, 2H), 7.12 (dd, J=5.1, 3.4 Hz, 1H), 6.69 (d, J=6.9 Hz, 1H), 2.47 (s, 3H); 13 C NMR(126 MHz, CDCl3) δ: 145.8, 144.5, 140.0, 138.2, 134.7, 134.0, 130.2, 129.4,129.0, 128.2, 125.1, 121.6, 120.7, 116.4, 111.8, 109.6, 21.5. HRMS (ESI)calcd for C 20 H 15 N5Cl [M+H] ＋ 360.1008, found 360.1010; The reaction formula is shown below: .

[0028] Example 12 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolvated, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A12, 792.2 mg, with a yield of 98%. 1 H NMR (500 MHz, CDCl3) δ: 8.41~8.20 (m, 1H), 7.69~7.46 (m, 4H), 7.46~7.31 (m, 4H), 7.22~7.09 (m, 1H), 6.69 (d, J= 6.1 Hz, 1H), 2.46 (s, 3H); 13 CNMR (126 MHz, CDCl3) δ: 145.8, 144.5, 140.0, 138.3, 137.8, 134.0, 131.9,130.7, 129.4, 128.5, 125.1, 123.0, 121.6, 120.7, 116.4, 111.8, 109.6, 21.5.HRMS (ESI) calcd for C 20 H 15 N5Br [M+H] ＋ 404.0499, found 404.0505; The reaction formula is shown below: .

[0029] Example 13 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolvated, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A13, 638.0 mg, with a yield of 94%. 1H NMR (500 MHz, CDCl3) δ: 8.21 (d, J=8.1 Hz, 1H), 7.69 (d, J=9.0 Hz, 1H), 7.48 (dt, J=14.9, 7.2 Hz, 2H), 7.28 (d, J=12.6 Hz, 3H), 7.20 (d, J=7.9 Hz, 1H), 6.99 (d, J=7.7 Hz, 2H), 6.57 (d, J=6.8 Hz, 1H), 2.24 (s, 3H), 1.74 (s, 3H); 13 C NMR (126 MHz, CDCl3) δ: 145.7, 145.2, 143.5, 138.7, 137.3,135.4, 129.5, 129.4, 128.8, 126.8, 124.9, 120.6, 116.1, 114.6, 111.8, 110.0,21.2, 17.1. HRMS (ESI) calcd for C 21 H 18 N5[M+H] ＋ 340.1554, found 340.1556; The reaction formula is shown below: .

[0030] Example 14 The following compounds were added to a 100 mL three-necked flask: imidazo[1,2-α]pyridine (2 mmol) and benzotriazole (2 mmol), followed by g-C3N4 (0.021 mol). Then, 10 mL of acetone / water (1:6) was added. The mixture was irradiated with a blue LED lamp under air conditions and stirred at room temperature. The reaction mixture was monitored by TLC until the starting material spot disappeared. The reaction mixture was then filtered, the filtrate was desolvated, dried, and separated by silica gel column chromatography to obtain the target product, imidazo[1,2-α]pyridine compound A14, 743.8 mg, with a yield of 96%. 1 H NMR (500 MHz, CDCl3) δ: 8.31~8.22 (m, 1H), 7.81 (d, J=9.1 Hz, 1H), 7.52 (ddd, J=18.7, 13.9, 8.5 Hz, 9H), 7.39 (t, J=7.5 Hz, 3H), 7.31 (t, J=7.2 Hz, 1H), 7.22~7.15 (m, 1H), 6.86 (t, J=6.8 Hz, 1H); 13C NMR (126 MHz, CDCl3) δ: 145.9, 141.9, 141.4, 141.3, 140.2, 134.0, 130.4, 129.4, 128.7, 128.1, 127.3, 127.3, 127.1, 126.8, 125.1, 122.4, 120.7, 118.1, 113.6, 109.8.HRMS (ESI) calcd for C 25 H 18 N5[M+H] ＋ 388.1556, found 388.1556; The reaction formula is shown below: .

[0031] Example 15 Add the following to a 100 mL three-necked flask: imidazo[1,2-α]pyridine compound (2 mmol) and benzotriazole compound (2 mmol), followed by g-C3N4 (0.021 mol). Add 10 mL of acetone / water (1:6), irradiate with a blue LED lamp under air, stir at room temperature, monitor the starting material by TLC, and stop the reaction when the starting material spot disappears. Filter the reaction solution, remove solvent from the filtrate, dry, and separate by silica gel column chromatography to obtain the target product imidazo[1,2-α]pyridine compound A15 617.7 mg, with a yield of 91%. 1 H NMR (500 MHz, CDCl3) δ: 8.18 (d, J=6.9 Hz, 1H), 7.63 (d, J=9.1 Hz, 1H), 7.49~7.37 (m, 2H), 7.32 (dd, J=13.1, 10.3 Hz, 2H), 7.18 (d, J=6.8 Hz, 1H), 7.14 (d, J=9.2 Hz, 1H), 7.11~7.04 (m, 1H), 6.95 (d, J=7.9 Hz, 2H), 2.18 (d, J=11.8 Hz, 6H); 13 C NMR (126 MHz, CDCl3) δ: 145.8, 143.1, 141.3,138.7, 134.1, 129.9, 129.4, 128.7, 126.8, 125.0, 123.7, 120.6, 120.0, 117.2,111.5, 109.9, 21.2, 18.2. HRMS (ESI) calcd for C 21 H 18N5[M+H] ＋ 340.1554, found 340.1556; The reaction formula is shown below: .

[0032] Application examples The antibacterial activity was determined using the mycelial growth rate method: First, the prepared potato dextrose agar medium was placed in an autoclave and autoclaved at 120 ℃ for 30 min. 20.0 mg of the target compound synthesized in the above examples was weighed and dissolved in 2.0 mL of acetone to obtain a product solution with a concentration of 10000 mg / L. Then, 0.25 mL of the product solution was added to 1.0 mL of acetone to dilute it to a product solution with a concentration of 1000 mg / L. The sterile operating table and tools were sterilized under UV light for 30 min before use. The culture dishes were labeled in advance. While still hot, the product solution was added to PDA medium, mixed well, and quickly poured into sterile culture dishes. After cooling and solidification, acetone was added as a control. Holes were punched in the mycelial cake using a punch, and the inoculation needle was used to transfer the mycelial cake to the center of the culture dish. After inoculation, the culture dishes were sealed with sealing film and placed in a constant temperature incubator for regular observation. Each treatment was repeated three times. When the mycelia in the control group reached 80% coverage in the culture dish, the colony diameter was measured using the cross-sectional method. The formula for the inhibition rate of antibacterial activity is as follows: Mycelial growth inhibition rate = (Control colony diameter - Treated colony diameter) / Control colony diameter × 100% The antifungal activities (inhibition rate %) of the imidazo[1,2-α]pyridine compounds (A1~A15) prepared in Examples 1~15 against *A. chinensis*, *A. anthracnose*, *A. gray mold*, *A. take-all*, and *A. wilt* of cucumber are shown in Table 1 below: Table 1. Antibacterial activity (inhibition rate %) of imidazo[1,2-α]pyridine compounds As shown in Table 1, the imidazo[1,2-α]pyridine compounds prepared in this invention have significant antibacterial activity and are promising for development into antibacterial drugs.

Claims

1. An imidazo[1,2-α]pyridine compound, characterized in that, The structural formula of the imidazo[1,2-α]pyridine compound is shown in Formula III below: Ⅲ R 1 It is one of H, alkyl, phenyl, methoxy, or halogen; R 2 It is one of H, alkyl, phenyl, methoxy, or halogen; R 3 It is one of H, alkyl, phenyl, methoxy, halogen, or forms a benzo[a] ring with a benzene ring.

2. A method for preparing the imidazo[1,2-α]pyridine compound according to claim 1, characterized in that, Imidazolo[1,2-α]pyridine compound I, benzotriazole compound II, and g-C3N4 were mixed in a solvent and reacted under air irradiation with a blue LED lamp. After the reaction was completed, the mixture was filtered, and the filtrate was desolvated, dried, and separated by column chromatography to obtain imidazo[1,2-α]pyridine compound III. The reaction formula is shown below: 。 3. The method for preparing imidazo[1,2-α]pyridine compounds according to claim 2, characterized in that, The molar ratio of the imidazo[1,2-α]pyridine compound I and the triazole compound II is 1:1 to 1.

3.

4. The method for preparing imidazo[1,2-α]pyridine compounds according to claim 2, characterized in that, The molar ratio of the imidazo[1,2-α]pyridine compound I to g-C3N4 is 2:0.02~0.

025.

5. The method for preparing imidazo[1,2-α]pyridine compounds according to claim 2, characterized in that, The solvent is a mixture of acetone and water, or ethanol and water, with a volume ratio of acetone or ethanol and water of 1:6 to 8.

6. The method for preparing imidazo[1,2-α]pyridine compounds according to claim 2, characterized in that, The reaction process was monitored by TLC until the starting material point disappeared.

7. The method for preparing imidazo[1,2-α]pyridine compounds according to claim 2, characterized in that, The column chromatography separation method described is silica gel column chromatography separation.

8. The use of an imidazo[1,2-α]pyridine compound as described in claim 1 or an imidazo[1,2-α]pyridine compound prepared by any one of claims 2 to 7 in the preparation of antibacterial agents.

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