**3. Experimental section**

#### **3.1 The optimization of the reaction conditions**

The optimization of the reaction is done using different solvents and also solvent free condition was applied and the reaction carried out under ultrasound irradiation. When the reaction was performed without solvent the yield obtained was in trace amount. When different solvent like acetonitrile, toluene and ethanol it the yield was less and the time taken for completion of reaction was more. But using (CAN) (10 mol %) EtOH-H2O (2:2) (entry 9) at 50–60°C for 35 min. we got good yield in less time and thus the reaction was optimized. The results were summarized in (**Table 1)**.

**General Procedure for the synthesis 3-aminoindazole** (**3a-h**)**:-** A mixture of benzonitrile (**1a-h**) (1.0 mmol), hydrazine (**2a-h**) (1.2 mmol) and (CAN) (10 mol) in solvent EtOH-H2O (2:2) were taken in single neck round bottom flask and the flask containing reaction mixture was kept in the ultrasonic bath and was irradiated at 50-60°C for about 30–40 min. (the progress of reaction was monitored by TLC at different interval) separately as indicated in (**Table 2**). After the reaction was completed the reaction mass was poured on crushed ice. The obtained solid was


filtered, washed with water and dried. The crude compound was crystallized using

**Comp. R R' product m.p (°C) Yield (%) 3a** H Me 95–97 90

*Eco-Friendly, Green Approach for Synthesis of Bio-Active Novel 3-Aminoindazole Derivatives*

*DOI: http://dx.doi.org/10.5772/intechopen.95565*

**3b** H H 150–152 87

**3c** 5-Br Me 133–135 93

**3d** 5-Cl Me 130–132 89

**3e** 6-OMe H 116–120 90

**3f** 4-Br H 171–174 95

**3 g** 5-I H 177–179 93

**3 h** 5-F H 165–167 90

aliphatic), 2830 (C-H sym. Str., aliphatic), 3054 (C-H str., aromatic),1540 (C=N str., Indazolyl), 1342 (C-N str.), 1504,1465 (C=C str., aromatic), 1119, 1126 (C-H i.

**H NMR δ ppm (DMSO-***d6***):** δ 3.79 (s, 3H, -CH3), 5.36 (s, 2H, Amine), 7.2–7.8

**13C-NMR (100 MHz, DMSO):** δ 35.52, 110.06, 112.34, 118.15, 122.83, 128.64,

, 271[M + Na]<sup>+</sup>

**Elemental Analysis:** Calcd. For C8H9N3; calculated: C, 65.29; H, 6.16; N, 28.55

**)**: 3422 (N-H str., -Amine),2982,2942 (C-H asym. Str.

H NMR, physical data, mass, IR

, 249[M + Na + H]<sup>+</sup> .

DMF-Ethanol. Their structure was confirmed by <sup>1</sup>

*CAN catalyze synthesis of 3-aminoindazole under ultrasound irradiation (3a-3 h).*

p. def., aromatic), 867 (C-H o.o.p. def., aromatic). **<sup>1</sup>**

**1-methyl-1H-indazol-3-amine (3a):**

**LCMS (ESI+)** *m/z***:** 148[M + 1]<sup>+</sup>

Found: C, 64.54; H, 6.19; N, 27.95.

and elemental analysis.

(m,4H, Ar-H).

**79**

**Table 2.**

139.45, 147.50 ppm.

**IR (KBr, υmax in cm<sup>1</sup>**

#### **Table 1.**

*Optimizing of the reaction conditions for 5-bromo-1-methyl-1H-indazol-3-amine (3c).*


*Eco-Friendly, Green Approach for Synthesis of Bio-Active Novel 3-Aminoindazole Derivatives DOI: http://dx.doi.org/10.5772/intechopen.95565*

**Table 2.**

gel60F254 and visualizing the spot in UV Cabinet and iodine chamber. The melting points were note down in open capillary in paraffin bath and are uncorrected. <sup>1</sup>

chromatography on silica gel (60–120 mesh). Elemental (CHN) examination was done using Thermo Scientific (Flash-2000), the compounds were investigated for carbon, hydrogen and nitrogen and the results found are in good agreement with

The optimization of the reaction is done using different solvents and also solvent free condition was applied and the reaction carried out under ultrasound irradiation. When the reaction was performed without solvent the yield obtained was in trace amount. When different solvent like acetonitrile, toluene and ethanol it the yield was less and the time taken for completion of reaction was more. But using (CAN) (10 mol %) EtOH-H2O (2:2) (entry 9) at 50–60°C for 35 min. we got good yield in less time and thus the reaction was optimized. The results were summarized

**General Procedure for the synthesis 3-aminoindazole** (**3a-h**)**:-** A mixture of benzonitrile (**1a-h**) (1.0 mmol), hydrazine (**2a-h**) (1.2 mmol) and (CAN) (10 mol) in solvent EtOH-H2O (2:2) were taken in single neck round bottom flask and the flask containing reaction mixture was kept in the ultrasonic bath and was irradiated at 50-60°C for about 30–40 min. (the progress of reaction was monitored by TLC at different interval) separately as indicated in (**Table 2**). After the reaction was completed the reaction mass was poured on crushed ice. The obtained solid was

**Entry CAN mol (%) Solvent Time (min) Yield (%) 1** — — 80 5 5 MeCN 60 40 10 MeCN 60 58 5 Toluene 70 53 10 Toluene 70 60 5 EtOH 60 68 10 EtOH 60 76 5 EtOH-H2O (2:2) 35 80 10 EtOH-H2O (2:2) **35 93** 15 EtOH-H2O (2:2) 35 86

*Optimizing of the reaction conditions for 5-bromo-1-methyl-1H-indazol-3-amine (3c).*

). The compounds are purified by using column

NMR spectra are logged on a Bruker AM 400 instrument (400 MHz) using tetramethylsilane (TMS) as an internal reference and DMSO-d6 as solvent. Chemical Shifts are specified in parts per million (ppm). Positive-ion Electro Spray Ionization (ESI) mass spectra were acquired with a Waters Micromass Q–TOF Micro, Mass Spectrophotometer. IR spectra were recorded on a Shimadzu IR Spec-

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trophotometer (KBr, υmax in cm<sup>1</sup>

**3.1 The optimization of the reaction conditions**

the calculated values.

in (**Table 1)**.

**Table 1.**

**78**

**3. Experimental section**

H

*CAN catalyze synthesis of 3-aminoindazole under ultrasound irradiation (3a-3 h).*

filtered, washed with water and dried. The crude compound was crystallized using DMF-Ethanol. Their structure was confirmed by <sup>1</sup> H NMR, physical data, mass, IR and elemental analysis.

#### **1-methyl-1H-indazol-3-amine (3a):**

**IR (KBr, υmax in cm<sup>1</sup> )**: 3422 (N-H str., -Amine),2982,2942 (C-H asym. Str. aliphatic), 2830 (C-H sym. Str., aliphatic), 3054 (C-H str., aromatic),1540 (C=N str., Indazolyl), 1342 (C-N str.), 1504,1465 (C=C str., aromatic), 1119, 1126 (C-H i. p. def., aromatic), 867 (C-H o.o.p. def., aromatic). **<sup>1</sup>**

**H NMR δ ppm (DMSO-***d6***):** δ 3.79 (s, 3H, -CH3), 5.36 (s, 2H, Amine), 7.2–7.8 (m,4H, Ar-H).

**13C-NMR (100 MHz, DMSO):** δ 35.52, 110.06, 112.34, 118.15, 122.83, 128.64, 139.45, 147.50 ppm.

**LCMS (ESI+)** *m/z***:** 148[M + 1]<sup>+</sup> , 271[M + Na]<sup>+</sup> , 249[M + Na + H]<sup>+</sup> .

**Elemental Analysis:** Calcd. For C8H9N3; calculated: C, 65.29; H, 6.16; N, 28.55 Found: C, 64.54; H, 6.19; N, 27.95.

**General Reaction:- Synthesis of compounds Indazole (3a-3 h) Derivatives.**

str., Indazolyl), 1346 (C-N str.), 1506,1460 (C=C str., aromatic), 1113, 1120 (C-H i.

*Eco-Friendly, Green Approach for Synthesis of Bio-Active Novel 3-Aminoindazole Derivatives*

**H NMR δ ppm (DMSO-***d6***)**: δ 3.73 (s, 3H, -CH3), 5.43 (s, 2H, -NH2), 6.7 (d, 1H, Ar-H), 7.2 (d, 1H, Ar-H), 7.5 (d, 1H, Ar-H), 12.4 (s, 1H, -NH of ring). **13C-NMR δ ppm (DMSO-***d6***):** δ 55.09, 95.02, 105.8, 106.8, 127.04, 142.02,

, 187 [M + Na]<sup>+</sup>

**Elemental Anal**.Calcd. For C8H9N3O; calculated: C, 58.88; H, 5.56; N, 25.75

aliphatic), 2835 (C-H sym. Str., aliphatic), 3052 (C-H str., aromatic), 1541 (C=N str., Indazolyl), 1347 (C-N str.), 1504,1466 (C=C str., aromatic), 1117, 1125 (C-H i.

**H NMR δ ppm (DMSO-***d6***)**: 5.38 (s, 2H, -NH2), 7.4(d, 1H, Ar-H), 7.7(d, 1H,

**13C-NMR δ ppm (DMSO-***d6***)**: 107.04, 113.34, 120.05, 122.03, 124.22, 143.10,

**Elemental Anal**.Calcd. For C7H6BrN3; calculated: C, 39.65; H, 2.85; N, 19.82

aliphatic), 2836 (C-H sym. Str., aliphatic), 3055 (C-H str., aromatic), 1541 (C=N str., Indazolyl), 1343 (C-N str.), 1505,1467 (C=C str., aromatic), 1120, 1125 (C-H i.

**13C-NMR δ ppm (DMSO-***d6***):** 88.3, 110.18, 115.37, 129.15, 134.23, 128.62,

**Elemental Anal**.Calcd. For C7H6IN3; calculated: C, 32.46; H, 2.33; N, 16.22

aliphatic), 2835 (C-H sym. Str., aliphatic), 3056 (C-H str., aromatic), 1546 (C=N str., Indazolyl), 1347 (C-N str.), 1502,1465 (C=C str., aromatic), 1119, 1126 (C-H i.

**H NMR δ ppm (DMSO-***d6***):** 4.98 (s, 2H, -NH2),), 7.1(d, 1H, Ar-H), 7.6(d, 1H,

**13C-NMR δ ppm (DMSO-***d6***):** 107.12, 110, 112.17, 115.17, 134.23, 149.81, 153.32.

Benzonitrile (**1a-h**) is reacted with hydrazine (**2a-h**) in presence of catalyst ceric (IV) ammonium nitrate (CAN) in solvent EtOH-H2O by using ultrasonic irradiation which undergoes cyclocondensation reaction to give substituted 3-aminoindazole **(3a-h**). The physical constants like melting point and solubility were determined for all the intermediate and final products. At every stage the reaction is monitored with TLC. Newly synthesized compound have been characterized on the basis of

, 282[M + Na]<sup>+</sup>

**Elemental Anal**.Calcd. For C7H6FN3; calculated: C, 55.63; H, 4.00; N, 27.80

p. def., aromatic), 865 (C-H o.o.p. def., aromatic),556 (C-Br str., Ar-Br). **<sup>1</sup>**

**H NMR δ ppm (DMSO-***d6***):** 5.44 (s, 2H, -NH2),), 7.4(d, 1H, Ar-H), 7.7(d, 1H,

p. def., aromatic), 861 (C-H o.o.p. def., aromatic),556 (C-Br str., Ar-Br). **<sup>1</sup>**

, 235[M + Na]<sup>+</sup>

p. def., aromatic), 866 (C-H o.o.p. def., aromatic),553 (C-Br str., Ar-Br). **<sup>1</sup>**

, 188[M + Na + H]<sup>+</sup>

, 236[M + Na + H]<sup>+</sup> .

**)**: 3421 (N-H str., -Amine), 2984, 2944 (C-H asym. Str.

**)**: 3419 (N-H str., -Amine), 2984, 2945 (C-H asym. Str.

, 282[M + Na]<sup>+</sup>

**)**: 3425 (N-H str., -Amine), 2983, 2943 (C-H asym. Str.

, 283 [M + Na + H]<sup>+</sup> .

H NMR, 13CNMR and mass

.

, 283[M + Na + H]<sup>+</sup> .

p. def., aromatic), 865 (C-H o.o.p. def., aromatic),553 (C-Br str., Ar-Br). **<sup>1</sup>**

149.05, and 153.12.

**LCMS (ESI+)** *m/z*: 164[M + 1]<sup>+</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.95565*

149.32. LCMS (ESI+) *m/z*: 212[M + 1]<sup>+</sup>

Found: C, 39.62; H, 2.82; N, 19.78. **5-iodo-1H-indazol-3-amine (3 g):**

Found: C, 32.35; H, 2.36; N, 15.98.

**IR (KBr, υmax in cm<sup>1</sup>**

**IR (KBr, υmax in cm<sup>1</sup>**

**6-bromo-1H-indazol-3-amine (3f):**

Ar-H), 7.8 (s, 1H, Ar-H), 12.4 (s, 1H, ring-N-H).

Ar-H), 8.2 (s, 1H, Ar-H), 12.4 (s, 1H, ring -N-H).

Ar-H), 7.9 (s, 1H, Ar-H), 12.41 (s, 1H, ring -N-H).

spectral data and elemental analysis such as FT-IR, <sup>1</sup>

spectra and they also screened for antimicrobial activities.

140.31, 149.81 LCMS (ESI+) *m/z*: 259[M + 1]<sup>+</sup>

**5-fluoro-1H-indazol-3-amine (3 h):**

**LCMS (ESI+)** *m/z***:** 259[M + 1]<sup>+</sup>

**3.2 Physico-chemical characterization**

Found: C, 55.67; H, 3.98; N, 27.40.

**81**

Found: C, 58.30; H, 5.43; N, 25.70.

**IR (KBr, υmax in cm<sup>1</sup>**

**1-H-Indazol-3-amine (3b):**

**IR (KBr, υmax in cm<sup>1</sup> ):** 3420 (N-H str., -Amine), 2980, 2941 (C-Hasym. str. aliphatic), 2833 (C-H sym. Str., aliphatic), 3051 (C-H str., aromatic),1544 (C=N str., Indazolyl), 1343 (C-N str.), 1503,1464 (C=C str., aromatic), 1116, 1123 (C-H i. p. def., aromatic), 864 (C-H o.o.p. def., aromatic),554 (C-Br str., Ar-Br). **<sup>1</sup>**

**H NMR δ ppm (DMSO-***d6***):** 5.41 (s, 2H, -NH2), 12.4 (s, 1H, ring-N-H), 7.2–7.7 (m,4H, Ar-H).

**13C NMR δ ppm (DMSO-***d6***):** δ 41.55, 108.01, 113.34, 117.75, 126.88, 128.62, 141.59, **LCMS (ESI+)** *m/z***:** 134[M + 1]<sup>+</sup> ,157[M + Na]<sup>+</sup> , 158[M + Na + H]<sup>+</sup> .

**Elemental Analysis:** Calcd. For C7H7N3; calculated: C, 63.14; H, 5.30; N, 31.56Found: C, 63.17; H, 5.34; N, 31.34.

**5-bromo-1-methyl-1H-indazol-3-amine (3c):**

**IR (KBr, υmax in cm<sup>1</sup> )**: 3424 (N-H str., -Amine), 2983,2943 (C-H asym. Str. aliphatic), 2834 (C-H sym. Str., aliphatic), 3052 (C-H str., aromatic),1541 (C=N str., Indazolyl), 1344 (C-N str.), 1501,1464 (C=C str., aromatic), 1116, 1122 (C-H i.

p. def., aromatic), 861 (C-H o.o.p. def., aromatic),556 (C-Br str., Ar-Br). **<sup>1</sup> H NMR δ ppm (DMSO-***d6***):** 3.65 (s, 3H, -CH3), 5.47 (s, 2H, -NH2), 7.5–7.6 (d, 2H, Ar-H), 7.93 (s, 1H, Ar-H).

**13C NMR δ ppm (DMSO-***d6***):** 34.55, 109.01, 110.34, 115.75, 122.88, 128.62, 139.59, 147.69.

**LCMS (ESI+)** *m/z***:** 225[M + 1]<sup>+</sup> , 248[M + Na]<sup>+</sup> , 249[M + Na + H]<sup>+</sup> .

**Elemental Analysis:** Calcd. For C8H8BrN3; calculated: C, 42.50; H, 3.57; Br, 35.34; N, 18.59 Found: C, 42.45; H, 3.59; N, 18.62.

**5-chloro-1-methyl-1H-indazol-3-amine (3d):**

**IR (KBr, υmax in cm<sup>1</sup> )**: 3423 (N-H str., -Amine), 2976, 2943 (C-H asym. Str. aliphatic), 2834 (C-H sym. Str., aliphatic),3053 (C-H str., aromatic), 1541 (C=N str., Indazolyl), 1345 (C-N str.), 1501,1462 (C=C str., aromatic), 1114, 1122 (C-H i. p. def., aromatic), 863 (C-H o.o.p. def., aromatic),554 (C-Br str., Ar-Br). **<sup>1</sup>**

**H NMR δppm (DMSO-***d6***):** δ 3.81 (s, 3H, -CH3), 5.36 (s, 2H, -NH2),7.3–7.5(d, 2H, Ar-H), 7.85 (s, 1H, Ar-H).

**13CNMR δ ppm (DMSO-***d6***):** δ 35.41, 110.03, 114.34, 120.75, 125.88, 126.62, 136.59, 146.61.

**LCMS (ESI+)** *m/z***:** 182[M + 1]<sup>+</sup> , 205[M + Na]<sup>+</sup> , 206[M + Na + H]+ .

Elemental Anal.Calcd. For C8H8ClN3; calculated: C, 52.90; H, 4.44; N, 23.14 Found: C, 52.93; H, 4.40; N, 23.15.

**4-methoxy-1H-indazol-3-amine (3e):**

**IR (KBr, υmax in cm<sup>1</sup> ):** 3426 (N-H str., -Amine), 2983, 2943 (C-H asym. Str. aliphatic), 2834 (C-H sym. Str., aliphatic), 3053 (C-H str., aromatic), 1542 (C=N

*Eco-Friendly, Green Approach for Synthesis of Bio-Active Novel 3-Aminoindazole Derivatives DOI: http://dx.doi.org/10.5772/intechopen.95565*

str., Indazolyl), 1346 (C-N str.), 1506,1460 (C=C str., aromatic), 1113, 1120 (C-H i. p. def., aromatic), 865 (C-H o.o.p. def., aromatic),553 (C-Br str., Ar-Br). **<sup>1</sup>**

**H NMR δ ppm (DMSO-***d6***)**: δ 3.73 (s, 3H, -CH3), 5.43 (s, 2H, -NH2), 6.7 (d, 1H, Ar-H), 7.2 (d, 1H, Ar-H), 7.5 (d, 1H, Ar-H), 12.4 (s, 1H, -NH of ring).

**13C-NMR δ ppm (DMSO-***d6***):** δ 55.09, 95.02, 105.8, 106.8, 127.04, 142.02, 149.05, and 153.12.

**LCMS (ESI+)** *m/z*: 164[M + 1]<sup>+</sup> , 187 [M + Na]<sup>+</sup> , 188[M + Na + H]<sup>+</sup> .

**Elemental Anal**.Calcd. For C8H9N3O; calculated: C, 58.88; H, 5.56; N, 25.75 Found: C, 58.30; H, 5.43; N, 25.70.

**6-bromo-1H-indazol-3-amine (3f):**

**General Reaction:- Synthesis of compounds Indazole (3a-3 h) Derivatives.**

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aliphatic), 2833 (C-H sym. Str., aliphatic), 3051 (C-H str., aromatic),1544 (C=N str., Indazolyl), 1343 (C-N str.), 1503,1464 (C=C str., aromatic), 1116, 1123 (C-H i.

**H NMR δ ppm (DMSO-***d6***):** 5.41 (s, 2H, -NH2), 12.4 (s, 1H, ring-N-H), 7.2–7.7

**13C NMR δ ppm (DMSO-***d6***):** δ 41.55, 108.01, 113.34, 117.75, 126.88, 128.62, 141.59,

,157[M + Na]<sup>+</sup>

**Elemental Analysis:** Calcd. For C7H7N3; calculated: C, 63.14; H, 5.30; N,

aliphatic), 2834 (C-H sym. Str., aliphatic), 3052 (C-H str., aromatic),1541 (C=N str., Indazolyl), 1344 (C-N str.), 1501,1464 (C=C str., aromatic), 1116, 1122 (C-H i.

**H NMR δ ppm (DMSO-***d6***):** 3.65 (s, 3H, -CH3), 5.47 (s, 2H, -NH2), 7.5–7.6

**13C NMR δ ppm (DMSO-***d6***):** 34.55, 109.01, 110.34, 115.75, 122.88, 128.62,

**Elemental Analysis:** Calcd. For C8H8BrN3; calculated: C, 42.50; H, 3.57; Br,

aliphatic), 2834 (C-H sym. Str., aliphatic),3053 (C-H str., aromatic), 1541 (C=N str., Indazolyl), 1345 (C-N str.), 1501,1462 (C=C str., aromatic), 1114, 1122 (C-H i.

**H NMR δppm (DMSO-***d6***):** δ 3.81 (s, 3H, -CH3), 5.36 (s, 2H, -NH2),7.3–7.5(d,

**13CNMR δ ppm (DMSO-***d6***):** δ 35.41, 110.03, 114.34, 120.75, 125.88, 126.62,

Elemental Anal.Calcd. For C8H8ClN3; calculated: C, 52.90; H, 4.44; N, 23.14

aliphatic), 2834 (C-H sym. Str., aliphatic), 3053 (C-H str., aromatic), 1542 (C=N

, 205[M + Na]<sup>+</sup>

p. def., aromatic), 863 (C-H o.o.p. def., aromatic),554 (C-Br str., Ar-Br). **<sup>1</sup>**

, 248[M + Na]<sup>+</sup>

p. def., aromatic), 861 (C-H o.o.p. def., aromatic),556 (C-Br str., Ar-Br). **<sup>1</sup>**

p. def., aromatic), 864 (C-H o.o.p. def., aromatic),554 (C-Br str., Ar-Br). **<sup>1</sup>**

**):** 3420 (N-H str., -Amine), 2980, 2941 (C-Hasym. str.

**)**: 3424 (N-H str., -Amine), 2983,2943 (C-H asym. Str.

**)**: 3423 (N-H str., -Amine), 2976, 2943 (C-H asym. Str.

**):** 3426 (N-H str., -Amine), 2983, 2943 (C-H asym. Str.

, 158[M + Na + H]<sup>+</sup>

, 249[M + Na + H]<sup>+</sup>

, 206[M + Na + H]+

.

.

.

**1-H-Indazol-3-amine (3b): IR (KBr, υmax in cm<sup>1</sup>**

**LCMS (ESI+)** *m/z***:** 134[M + 1]<sup>+</sup>

31.56Found: C, 63.17; H, 5.34; N, 31.34.

**IR (KBr, υmax in cm<sup>1</sup>**

(d, 2H, Ar-H), 7.93 (s, 1H, Ar-H).

**IR (KBr, υmax in cm<sup>1</sup>**

2H, Ar-H), 7.85 (s, 1H, Ar-H).

**LCMS (ESI+)** *m/z***:** 182[M + 1]<sup>+</sup>

**4-methoxy-1H-indazol-3-amine (3e):**

Found: C, 52.93; H, 4.40; N, 23.15.

**IR (KBr, υmax in cm<sup>1</sup>**

**LCMS (ESI+)** *m/z***:** 225[M + 1]<sup>+</sup>

35.34; N, 18.59 Found: C, 42.45; H, 3.59; N, 18.62. **5-chloro-1-methyl-1H-indazol-3-amine (3d):**

**5-bromo-1-methyl-1H-indazol-3-amine (3c):**

(m,4H, Ar-H).

139.59, 147.69.

136.59, 146.61.

**80**

**IR (KBr, υmax in cm<sup>1</sup> )**: 3421 (N-H str., -Amine), 2984, 2944 (C-H asym. Str. aliphatic), 2835 (C-H sym. Str., aliphatic), 3052 (C-H str., aromatic), 1541 (C=N str., Indazolyl), 1347 (C-N str.), 1504,1466 (C=C str., aromatic), 1117, 1125 (C-H i. p. def., aromatic), 866 (C-H o.o.p. def., aromatic),553 (C-Br str., Ar-Br). **<sup>1</sup>**

**H NMR δ ppm (DMSO-***d6***)**: 5.38 (s, 2H, -NH2), 7.4(d, 1H, Ar-H), 7.7(d, 1H, Ar-H), 7.8 (s, 1H, Ar-H), 12.4 (s, 1H, ring-N-H).

**13C-NMR δ ppm (DMSO-***d6***)**: 107.04, 113.34, 120.05, 122.03, 124.22, 143.10, 149.32. LCMS (ESI+) *m/z*: 212[M + 1]<sup>+</sup> , 235[M + Na]<sup>+</sup> , 236[M + Na + H]<sup>+</sup> .

**Elemental Anal**.Calcd. For C7H6BrN3; calculated: C, 39.65; H, 2.85; N, 19.82 Found: C, 39.62; H, 2.82; N, 19.78.

**5-iodo-1H-indazol-3-amine (3 g):**

**IR (KBr, υmax in cm<sup>1</sup> )**: 3419 (N-H str., -Amine), 2984, 2945 (C-H asym. Str. aliphatic), 2836 (C-H sym. Str., aliphatic), 3055 (C-H str., aromatic), 1541 (C=N str., Indazolyl), 1343 (C-N str.), 1505,1467 (C=C str., aromatic), 1120, 1125 (C-H i. p. def., aromatic), 861 (C-H o.o.p. def., aromatic),556 (C-Br str., Ar-Br). **<sup>1</sup>**

**H NMR δ ppm (DMSO-***d6***):** 5.44 (s, 2H, -NH2),), 7.4(d, 1H, Ar-H), 7.7(d, 1H, Ar-H), 8.2 (s, 1H, Ar-H), 12.4 (s, 1H, ring -N-H).

**13C-NMR δ ppm (DMSO-***d6***):** 88.3, 110.18, 115.37, 129.15, 134.23, 128.62, 140.31, 149.81 LCMS (ESI+) *m/z*: 259[M + 1]<sup>+</sup> , 282[M + Na]<sup>+</sup> , 283[M + Na + H]<sup>+</sup> .

**Elemental Anal**.Calcd. For C7H6IN3; calculated: C, 32.46; H, 2.33; N, 16.22 Found: C, 32.35; H, 2.36; N, 15.98.

**5-fluoro-1H-indazol-3-amine (3 h):**

**IR (KBr, υmax in cm<sup>1</sup> )**: 3425 (N-H str., -Amine), 2983, 2943 (C-H asym. Str. aliphatic), 2835 (C-H sym. Str., aliphatic), 3056 (C-H str., aromatic), 1546 (C=N str., Indazolyl), 1347 (C-N str.), 1502,1465 (C=C str., aromatic), 1119, 1126 (C-H i. p. def., aromatic), 865 (C-H o.o.p. def., aromatic),556 (C-Br str., Ar-Br). **<sup>1</sup>**

**H NMR δ ppm (DMSO-***d6***):** 4.98 (s, 2H, -NH2),), 7.1(d, 1H, Ar-H), 7.6(d, 1H, Ar-H), 7.9 (s, 1H, Ar-H), 12.41 (s, 1H, ring -N-H).

**13C-NMR δ ppm (DMSO-***d6***):** 107.12, 110, 112.17, 115.17, 134.23, 149.81, 153.32. **LCMS (ESI+)** *m/z***:** 259[M + 1]<sup>+</sup> , 282[M + Na]<sup>+</sup> , 283 [M + Na + H]<sup>+</sup> .

**Elemental Anal**.Calcd. For C7H6FN3; calculated: C, 55.63; H, 4.00; N, 27.80 Found: C, 55.67; H, 3.98; N, 27.40.

#### **3.2 Physico-chemical characterization**

Benzonitrile (**1a-h**) is reacted with hydrazine (**2a-h**) in presence of catalyst ceric (IV) ammonium nitrate (CAN) in solvent EtOH-H2O by using ultrasonic irradiation which undergoes cyclocondensation reaction to give substituted 3-aminoindazole **(3a-h**). The physical constants like melting point and solubility were determined for all the intermediate and final products. At every stage the reaction is monitored with TLC. Newly synthesized compound have been characterized on the basis of spectral data and elemental analysis such as FT-IR, <sup>1</sup> H NMR, 13CNMR and mass spectra and they also screened for antimicrobial activities.

The IR spectrum of **3c** showed strong band absorption bands at 3424 cm<sup>1</sup> due to -NH- stretch in amine while bands at 1541 cm<sup>1</sup> is observed due to C=N stretch in Indazolyl and absorption band at 556 cm<sup>1</sup> showsC-Br aromatic stretching and stretch at 1344 cm<sup>1</sup> was observed for C-N str group confirms the cyclisation to form 5-bromo-1-methyl-1H-indazol-3-amine**3c**. 1 H NMR of **3c** revealed a singlet signal at 3.65 ppm, at aliphatic region owing to three protons of -CH3 group attached to aromatic ring, one more singlet at δ 5.47 ppm confirm protons of

–NH2- group, Remaining <sup>1</sup>

C8H8BrN3.

**Figure 4.**

**83**

molecular ion at *(m/z)* value at 225[M + 1]<sup>+</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.95565*

H NMR signal is present at aromatic region as expected.

, and further supported by elemental

C<sup>13</sup> NMR also supported data singlet signal at δ34.55, ppm revealed one aliphatic carbon, of -CH3 attached to indazole ring. ESI-MS Mass spectra also confirm the

*Eco-Friendly, Green Approach for Synthesis of Bio-Active Novel 3-Aminoindazole Derivatives*

**Potent antibacterial/inhibition profile of 3-amino indazole (at different concentration) by agar disc-diffusion method: -** The entire novel synthesized heterocyclic compounds **3a-h** was screened for their *in-vitro* antimicrobial activity using disc-diffusion method. Their activity was compared with well-known commercial antibiotic Chloramphenicol. Antibacterial activity was determined by using Mueller Hinton Agar obtained from Hi media Ltd., Mumbai. Petri plates were prepared by pouring 10 mL of Mueller Hinton Agar for bacteria containing microbial culture was allowed to solidify. Test solutions were prepared with known weight of compound in DMSO and half diluted suitably to give the resultant

analysis data found to be in good agreement with the molecular formula of

*Antimicrobial activity of compound 3a-h against Gram - bacteria* S. aureus *and* P. vulgaris*.*


#### **Table 3.**

*Antibacterial profile of 3-aminoindazole derivative (3a-h) .*


#### **Table 4.**

*Antibacterial profile of 3-aminoindazole derivative (3a-h).*

*Eco-Friendly, Green Approach for Synthesis of Bio-Active Novel 3-Aminoindazole Derivatives DOI: http://dx.doi.org/10.5772/intechopen.95565*

–NH2- group, Remaining <sup>1</sup> H NMR signal is present at aromatic region as expected. C<sup>13</sup> NMR also supported data singlet signal at δ34.55, ppm revealed one aliphatic carbon, of -CH3 attached to indazole ring. ESI-MS Mass spectra also confirm the molecular ion at *(m/z)* value at 225[M + 1]<sup>+</sup> , and further supported by elemental analysis data found to be in good agreement with the molecular formula of C8H8BrN3.

**Potent antibacterial/inhibition profile of 3-amino indazole (at different concentration) by agar disc-diffusion method: -** The entire novel synthesized heterocyclic compounds **3a-h** was screened for their *in-vitro* antimicrobial activity using disc-diffusion method. Their activity was compared with well-known commercial antibiotic Chloramphenicol. Antibacterial activity was determined by using Mueller Hinton Agar obtained from Hi media Ltd., Mumbai. Petri plates were prepared by pouring 10 mL of Mueller Hinton Agar for bacteria containing microbial culture was allowed to solidify. Test solutions were prepared with known weight of compound in DMSO and half diluted suitably to give the resultant

**Figure 4.** *Antimicrobial activity of compound 3a-h against Gram - bacteria* S. aureus *and* P. vulgaris*.*

The IR spectrum of **3c** showed strong band absorption bands at 3424 cm<sup>1</sup> due to -NH- stretch in amine while bands at 1541 cm<sup>1</sup> is observed due to C=N stretch in Indazolyl and absorption band at 556 cm<sup>1</sup> showsC-Br aromatic stretching and stretch at 1344 cm<sup>1</sup> was observed for C-N str group confirms the cyclisation to

signal at 3.65 ppm, at aliphatic region owing to three protons of -CH3 group attached to aromatic ring, one more singlet at δ 5.47 ppm confirm protons of

**Compd. Code Gram + ve Gram –ve**

**Zone of Inhibition (mm)**

**3a** 21 **22 21 20 17** 13 27 **24 21 18 17** 10 **3b** 23 21 **20** 18 16 **18** 25 22 19 16 14 09 **3c 25** 21 19 **20** 16 **15 28** 23 **21 17** 15 11 **3d** 23 22 **21 19 18** 15 27 24 **20 18 17** 12 **3e** 19 20 16 15 13 14 21 19 15 14 13 09 **3f** 24 **23 21 20 17 16** 25 23 **21 19** 15 08 **3 g** 23 20 18 17 16 13 23 22 21 16 14 10 **3 h** 20 18 16 15 13 11 26 21 17 15 12 09 **DMSO — — —— —— — — —— —— Std. Drug** Chloramphenicol **25 22 20 19 17 15 26 24 23 21 17 15**

**Zone of Inhibition (mm)**

**3a 26 24** 22 **21** 16 12 16 15 **12 11 10 09 3b** 24 21 19 18 17 **16** 16 14 10 09 06 07 **3c** 25 24 20 17 16 **15 17** 16 11 **10 09 08 3d 26** 23 21 20 **17** 11 14 10 08 08 07 **09 3e** 23 22 20 18 14 12 16 14 12 11 09 07 **3f** 25 **24** 22 20 **18 15** 17 **16** 11 10 **09 08 3 g** 21 20 17 16 14 11 15 13 11 10 08 07 **3 h** 22 21 20 18 16 13 14 12 10 08 06 05 **DMSO** — — —— —— — — —— —— **Std. Drug** Chloramphenicol **26 24 23 21 17 14 17 15 12 11 09 08**

*E. coli S.typhi* **Conc. (μg/mL) Conc. (μg/mL) 1000 500 250 125 63.5 31 1000 500 250 125 63.5 31**

1

*S. aureus P.vulgaris* **Conc. (μg/mL) Conc. (μg/mL) 1000 500 250 125 63.5 31 1000 500 250 125 63.5 31**

H NMR of **3c** revealed a singlet

form 5-bromo-1-methyl-1H-indazol-3-amine**3c**.

*Green Computing Technologies and Computing Industry in 2021*

*Antibacterial profile of 3-aminoindazole derivative (3a-h) .*

*Antibacterial profile of 3-aminoindazole derivative (3a-h).*

**Compd. Code Gram –ve**

**Table 3.**

**Table 4.**

**82**

concentration of 31-1000 μg/mL. Whatmann no.1 sterile filter paper discs (6 mm) were impregnated with solution and allowed to dry at room temperature. The discs were then applied and the plates were incubated at 37°C for 24 h (bacteria) and the inhibition zone (**Figure 6**) was measured as diameter in four directions and expressed as mean. The results of the antimicrobial screening are illustrated in the **Tables 3** and **4**. From the results it is clear that the compounds tested showed variable toxicity against different bacteria.

#### **3.3 Mechanism of inhibition/prohibition**

Gram-negative bacteria habitually owe low susceptibility as outer membrane of their cell wall not gets blocked/penetrated by drugs easily and factors like amount of peptidoglycan, receptors, and lipids availability, nature of crosslinking, autolytic enzymes activity greatly influence the bio-activity, permeation, and incorporation of the antibacterial drugs. There are three behaviors in which antibacterial drugs have thus far beenshown to exert their definite actions upon bacteria: 1) by interfering with the synthesis of the relatively rigid cell wall which

Maintains the structural integrity of the bacterial cell (2) by destructivethe elusive membrane, which encompasses the bacterial cytoplasm and assists as an essential osmotic barricade to the free diffusion of severalmetabolites and (3) by blocking cytoplasmic metabolic reactions which are involved in critical synthetic processes within the cell. Consequences of bioassay indicated that compound (**Figures 4** and **5**)

*Eco-Friendly, Green Approach for Synthesis of Bio-Active Novel 3-Aminoindazole Derivatives*

*DOI: http://dx.doi.org/10.5772/intechopen.95565*

*E.coli*. Remaining compounds exhibited reasonable activity against selected bacterial

In summary, in the present chapter we have described an efficient simple and reproducible method afforded various amino indazole derivatives (**3a-h)** in excellent yields, and without formation of undesirable side products. The synthetic protocol has been outlined in general reaction. At every stage the reaction was monitored with TLC. The physical constants like melting point and solubility were determined for all the intermediate and final products. Newly synthesized compound has been characterized on the basis of spectral data and elemental analysis

futuristic researchers, clinicians, and academicians involved in synthesizing and corresponding biological screening of innate activity of certain novel amino indazole heterocycleswe have described here novel series of Indazole **(3a-h)** derivative. The presented series of compounds were synthesized in decent yields. The structure and purity of newly synthesized compounds were established by spectroscopic investigation and chemical examination. Antibacterial screening of synthesized substituted indazole **(3a-h)** derivatives exhibited a potent bactericidal. Thus, it could be powerfully stimulates major advances in remarkable significant chemotherapeutics in medicine, biology and pharmacy. Overall these indazole disturb

HNMR, 13C NMR and mass spectra this chapter focused on helping

**3a, 3c, 3d, 3f** showed excellent activity against *S. aureus* and *P.vulgaris* and

strains.

**Figure 6.**

*Zone of inhibition in mm.*

**4. Conclusions**

such as FT-IR, <sup>1</sup>

**85**

**Figure 5.** *Antimicrobial activity of compound 3a-h against Gram - bacteria* E. coli *and* S. typhi*.*

*Eco-Friendly, Green Approach for Synthesis of Bio-Active Novel 3-Aminoindazole Derivatives DOI: http://dx.doi.org/10.5772/intechopen.95565*

**Figure 6.** *Zone of inhibition in mm.*

concentration of 31-1000 μg/mL. Whatmann no.1 sterile filter paper discs (6 mm) were impregnated with solution and allowed to dry at room temperature. The discs were then applied and the plates were incubated at 37°C for 24 h (bacteria) and the

Gram-negative bacteria habitually owe low susceptibility as outer membrane of their cell wall not gets blocked/penetrated by drugs easily and factors like amount of peptidoglycan, receptors, and lipids availability, nature of crosslinking, autolytic enzymes activity greatly influence the bio-activity, permeation, and incorporation of the antibacterial drugs. There are three behaviors in which antibacterial drugs have thus far beenshown to exert their definite actions upon bacteria: 1) by interfering with the synthesis of the relatively rigid cell wall which

inhibition zone (**Figure 6**) was measured as diameter in four directions and expressed as mean. The results of the antimicrobial screening are illustrated in the **Tables 3** and **4**. From the results it is clear that the compounds tested showed

variable toxicity against different bacteria.

*Green Computing Technologies and Computing Industry in 2021*

**3.3 Mechanism of inhibition/prohibition**

**Figure 5.**

**84**

*Antimicrobial activity of compound 3a-h against Gram - bacteria* E. coli *and* S. typhi*.*

Maintains the structural integrity of the bacterial cell (2) by destructivethe elusive membrane, which encompasses the bacterial cytoplasm and assists as an essential osmotic barricade to the free diffusion of severalmetabolites and (3) by blocking cytoplasmic metabolic reactions which are involved in critical synthetic processes within the cell. Consequences of bioassay indicated that compound (**Figures 4** and **5**) **3a, 3c, 3d, 3f** showed excellent activity against *S. aureus* and *P.vulgaris* and *E.coli*. Remaining compounds exhibited reasonable activity against selected bacterial strains.

## **4. Conclusions**

In summary, in the present chapter we have described an efficient simple and reproducible method afforded various amino indazole derivatives (**3a-h)** in excellent yields, and without formation of undesirable side products. The synthetic protocol has been outlined in general reaction. At every stage the reaction was monitored with TLC. The physical constants like melting point and solubility were determined for all the intermediate and final products. Newly synthesized compound has been characterized on the basis of spectral data and elemental analysis such as FT-IR, <sup>1</sup> HNMR, 13C NMR and mass spectra this chapter focused on helping futuristic researchers, clinicians, and academicians involved in synthesizing and corresponding biological screening of innate activity of certain novel amino indazole heterocycleswe have described here novel series of Indazole **(3a-h)** derivative. The presented series of compounds were synthesized in decent yields. The structure and purity of newly synthesized compounds were established by spectroscopic investigation and chemical examination. Antibacterial screening of synthesized substituted indazole **(3a-h)** derivatives exhibited a potent bactericidal. Thus, it could be powerfully stimulates major advances in remarkable significant chemotherapeutics in medicine, biology and pharmacy. Overall these indazole disturb

macromolecules like cytoplasmic membrane covering cytoplasm which acts selective barrier to control internal composition of cell. Amino indazole derivative particularly interrupted such functional roles of cytoplasmic membrane and ionic outflow that resulted cell destruction/death. Synthesized potent bioactive substituted indazole derivatives may open new possibilities in the successful treatment of several diseases due to promising antibacterial profile. So, ample scope exists in further research of this heterocycle especially innate selectivity of these compounds needs to carry out their chemotherapy as potent antibacterial aims to target cell membrane of range of Gram-negative bacteria as to derive novel drugs ofInventive era. Among the synthesized compounds most of the compounds exhibited good to moderate activity against selected strains *S. aureus, P. vulgaris* and *E. coli* while poor activity was evaluated for *S. typhi* (**Figure 5**). This variation in toxicity it may attribute due to union ofdifferent substituent attached to the core 3 aminoindazole which may enhances the biological activities of parent nucleus.

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