*3.2.4 7-Chloro-2-(2-nitrophenyl)-3,4-dihydroimidazo[4,5-b]indole (4d)*

Brownsolid, **IR (KBr) υ:** 3399, 3229, 2916, 2885, 1645, 1600, 1539, 1457, 1329, 1253, 1162, 1027, 885, 703, 647, 553 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 7.66–8.36 (m, 7H, aromatic protons), 8.96 (s, 1H, NH), 9.50 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 123.4, 123.8, 124.8, 127.1, 128.0, 128.6, 129.4, 133.9, 134.1, 134.4, 139.7, 148.7, 150.4, 160.6 ppm. Anal. Calcd for C15H9ClN4O2: C, 57.60; H, 2.91; N, 17.91 Found C, 57.51; H, 3.0; N, 17.94.

## *3.2.5 2-(3-Nitrophenyl)-3,4-dihydroimidazo[4,5-b]indole (4e)*

Brownsolid, **IR (KBr) υ:** 3315, 3194, 3066, 2978, 1662, 1623, 1572, 1482, 1353, 1286, 1135, 1025, 832, 797, 661, 542 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, DMSO) δ:** 7.58–8.55 (m, 8H, aromatic protons), 8.97 (s, 1H, NH), 9.67 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 122.3, 123.6, 125.2, 127.9, 128.4, 129.7, 130.4, 134.4, 134.5, 135.2, 139.0, 147.6, 161.7 ppm. Anal. Calcd for C15H10N4O2: C, 64.70; H, 3.63; N, 20.16 Found C, 64.51; H, 3.72; N, 20.23.

#### *3.2.6 7-Chloro-2-(3-nitrophenyl)-3,4-dihydroimidazo[4,5-b]indole (4f)*

Brownsolid, **IR (KBr) υ:** 3385, 3211, 3003, 2959, 1646, 1603, 1538, 1458, 1367, 1248, 1122, 1022, 831, 741, 635, 564 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, DMSO) δ:** 7.77–8.83 (m, 7H, aromatic protons), 9.13 (s, 1H, NH), 9.62 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 124.0, 126.6, 127.5, 127.6, 130.2, 130.7, 132.0, 133.6, 135.4, 139.1, 148.2, 160.8, 160.9 ppm. Anal. Calcd for C15H9ClN4O2: C, 57.61; H, 2.90; N, 17.92 Found C, 57.67; H, 2.90; N, 17.90.

#### *3.2.7 2-(3-Chlorophenyl)-3,4-dihydroimidazo[4,5-b]indole (4g)*

Brownsolid, **IR (KBr) υ:** 3405, 3217, 2948, 2909, 1671, 1617, 1568, 1454, 1371, 1283, 1134, 1018, 892, 754, 641, 577 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, DMSO) δ:** 7.60–8.56 (m, 9H, aromatic protons and 1H, NH), 9.69 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 123.8, 126.6, 128.8, 128.7, 130.1, 131.0, 131.6, 135.2, 137.0, 148.4, 160.6 ppm. Anal. Calcd for C15H10ClN3: C, 67.30; H, 3.77; N, 15.70 Found C, 67.29; H, 3.75; N, 15.70.

#### *3.2.8 7-Chloro-2-(3-chlorophenyl)-3,4-dihydroimidazo[4,5-b]indole (4h)*

Brownsolid, **IR (KBr) υ:** 3398, 3227, 2977, 2893, 1664, 1605, 1551, 1477, 1358, 1242, 1163, 1011, 844, 743, 650, 567 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 7.62–8.31 (m, 7H, aromatic protons), 8.90 (s, 1H, NH), 9.42 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 124.1, 125.8, 126.6, 128.6, 129.8, 130.3, 130.7, 133.2, 134.8, 135.2, 139.3, 149.0, 160.5 ppm. Anal. Calcd for C15H9Cl2N3: C, 59.62; H, 3.00; N, 13.91 Found C, 59.52; H, 3.05; N, 13.89.

**65**

*Eco-Friendly and Facile Synthesis of Substituted Imidazoles via Nano Zirconia Catalyzed…*

Brownsolid, **IR (KBr) υ:** 3362, 3255, 3015, 2882, 1669, 1620, 1565, 1482, 1375,

7.48–8.58 (m, 8H, aromatic protons), 9.45 (s, 1H, NH), 10.16 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 123.3, 127.8, 127.9, 128.7, 129.7, 134.9, 135.6, 136.2, 149.7, 161.3 ppm. Anal. Calcd for C15H10ClN3: C, 67.30; H, 3.77; N, 15.70 Found C,

Brownsolid, **IR (KBr) υ:** 3386, 3233, 3047, 2960, 1657, 1612, 1558, 1435, 1348,

Brownsolid, **IR (KBr) υ:** 3351, 3138, 3001, 2944, 2881, 1667, 1619, 1575, 1450,

(m, 7H, aromatic protons), 8.99 (s, 1H, NH), 9.35 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ**: 123.9, 125.8, 128.8, 129.8, 130.3, 133.0, 135.2, 136.0, 137.1, 149.1, 159.5 ppm. Anal. Calcd for C15H9Cl2N3: C, 59.62; H, 3.00; N, 13.91 Found C,

4.00 (s, 3H, CH3), 7.26–8.69 (m, 9H, aromatic protons and 1H, NH), 9.72 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 56.9, 122.2, 123.2, 125.9, 127.7, 127.4, 127.9, 128.7, 129.0, 129.6, 130.7, 131.2, 131.4, 131.5, 138.5, 139.7, 140.1, 143.9, 145.8, 154.6 ppm. Anal. Calcd for C16H13N3O: C, 72.99; H, 4.98; N, 15.96

*3.2.12 7-Chloro-2-(4-methoxyphenyl)-3,4-dihydroimidazo[4,5-b]indole (4l)*

C16H12ClN3O: C, 64.54; H, 4.06; N, 14.11 Found C, 64.70; H, 4.00; N, 14.10.

*3.2.13 1-(2-(3-Nitrophenyl)imidazo[4,5-b]indol-4(3H)-yl)ethanone (4m)*

*3.2.14 1-(2-(3-Chlorophenyl)imidazo[4,5-b]indol-4(3H)-yl)ethanone (4n)*

Brownsolid, **IR (KBr) υ:** 3370, 3259, 2991, 2911, 1675, 1614, 1558, 1480, 1436

Brownsolid, **IR (KBr) υ:** 3389, 3266, 2978, 2935, 1694, 1645, 1616, 1571, 1467,

1.91 (s, 3H, CH3), 7.22–8.51 (m, 8H, aromatic protons), 9.40 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 23.7, 122.1, 122.4, 123.2, 123.5, 124.8, 127.2, 127.4, 127.6, 128.2, 129.7, 130.1, 130.9, 133.0, 134.1, 134.4, 135.6, 138.0, 141.0, 148.7, 150.4, 160.3, 172.2 ppm. Anal. Calcd for C17H12N4O3: C, 63.75; H, 3.78; N, 17.49

Brownsolid, **IR (KBr) υ:** 3367, 3215, 2947, 2923, 1692, 1662 1607, 1580, 1477,

1.25 (s, 3H, CH3), 7.34–8.11 (m, 8H, aromatic protons), 9.36 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 23.6, 122.5, 124.1, 125.3, 126.6, 130.1, 130.4, 130.7,

3.61 (s, 3H, CH3), 7.44–8.47 (m, 8H, aromatic protons), 8.58 (s, 1H, NH), 9.36 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 61.8, 122.16, 122.29, 124.0, 125.3, 126.6, 130.1, 130.4, 132.3, 133.9, 135.5, 138.5, 148.1, 148.2, 157.8 ppm. Anal. Calcd for

*3.2.10 7-Chloro-2-(4-chlorophenyl)-3,4-dihydroimidazo[4,5-b]indole (4j)*

*3.2.11 2-(4-Methoxyphenyl)-3,4-dihydroimidazo[4,5-b]indole (4k)*

. **1H NMR (300 MHz, CDCl3) δ:**

. **1H NMR (300 MHz, CDCl3) δ:** 7.46–8.54

. **1H NMR (300 MHz, DMSO) δ:**

. **1H NMR (300 MHz, CDCl3) δ:**

. **1H NMR (300 MHz, CDCl3) δ:**

. **1H NMR (300 MHz, CDCl3) δ:**

*3.2.9 2-(4-Chlorophenyl)-3,4-dihydroimidazo[4,5-b]indole (4i)*

*DOI: http://dx.doi.org/10.5772/intechopen.82720*

1235, 1140, 1026, 890, 777, 663, 526 cm<sup>−</sup><sup>1</sup>

1282, 1153, 1019, 871, 742, 654, 552 cm<sup>−</sup><sup>1</sup>

1371, 1284, 1157, 1021, 863, 743, 654, 534 cm<sup>−</sup><sup>1</sup>

1377, 1291, 1186, 1049, 869, 745, 651, 522 cm<sup>−</sup><sup>1</sup>

1346, 1224, 1133, 1021, 823, 744, 641, 572 cm<sup>−</sup><sup>1</sup>

1359, 1272, 1144, 1042, 807, 735, 653, 546 cm<sup>−</sup><sup>1</sup>

Found C, 63.68; H, 3.88; N, 17.52.

Found C, 72.91; H, 5.04; N, 15.95.

67.31; H, 3.75; N, 15.73.

59.55; H, 3.10; N, 13.90.

*Eco-Friendly and Facile Synthesis of Substituted Imidazoles via Nano Zirconia Catalyzed… DOI: http://dx.doi.org/10.5772/intechopen.82720*

*3.2.9 2-(4-Chlorophenyl)-3,4-dihydroimidazo[4,5-b]indole (4i)*

*Nanocatalysts*

*3.2.3 2-(2-Nitrophenyl)-3,4-dihydroimidazo[4,5-b]indole (4c)*

1280, 1176, 1068, 864, 708, 667, 544 cm<sup>−</sup><sup>1</sup>

1253, 1162, 1027, 885, 703, 647, 553 cm<sup>−</sup><sup>1</sup>

N, 17.91 Found C, 57.51; H, 3.0; N, 17.94.

1286, 1135, 1025, 832, 797, 661, 542 cm<sup>−</sup><sup>1</sup>

20.16 Found C, 64.51; H, 3.72; N, 20.23.

1248, 1122, 1022, 831, 741, 635, 564 cm<sup>−</sup><sup>1</sup>

17.92 Found C, 57.67; H, 2.90; N, 17.90.

Found C, 67.29; H, 3.75; N, 15.70.

1242, 1163, 1011, 844, 743, 650, 567 cm<sup>−</sup><sup>1</sup>

N, 13.91 Found C, 59.52; H, 3.05; N, 13.89.

1371, 1283, 1134, 1018, 892, 754, 641, 577 cm<sup>−</sup><sup>1</sup>

64.69; H, 3.65; N, 20.14.

Brownsolid, **IR (KBr) υ:** 3332, 3201, 2995, 2917, 1658, 1623, 1549, 1485, 1348,

8.69 (m, 8H, aromatic protons), 9.67 (s, 1H, NH), 9.94 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 123.8, 126.7, 128.8, 129.8, 130.1, 131.8, 135.4, 135.8, 135.9, 148.3, 160.7 ppm. Anal. Calcd for C15H10N4O2: C, 64.74; H, 3.62; N, 20.13 Found C,

Brownsolid, **IR (KBr) υ:** 3399, 3229, 2916, 2885, 1645, 1600, 1539, 1457, 1329,

Brownsolid, **IR (KBr) υ:** 3315, 3194, 3066, 2978, 1662, 1623, 1572, 1482, 1353,

Brownsolid, **IR (KBr) υ:** 3385, 3211, 3003, 2959, 1646, 1603, 1538, 1458, 1367,

(m, 7H, aromatic protons), 9.13 (s, 1H, NH), 9.62 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 124.0, 126.6, 127.5, 127.6, 130.2, 130.7, 132.0, 133.6, 135.4, 139.1, 148.2, 160.8, 160.9 ppm. Anal. Calcd for C15H9ClN4O2: C, 57.61; H, 2.90; N,

Brownsolid, **IR (KBr) υ:** 3405, 3217, 2948, 2909, 1671, 1617, 1568, 1454,

**δ:** 7.60–8.56 (m, 9H, aromatic protons and 1H, NH), 9.69 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 123.8, 126.6, 128.8, 128.7, 130.1, 131.0, 131.6, 135.2, 137.0, 148.4, 160.6 ppm. Anal. Calcd for C15H10ClN3: C, 67.30; H, 3.77; N, 15.70

Brownsolid, **IR (KBr) υ:** 3398, 3227, 2977, 2893, 1664, 1605, 1551, 1477, 1358,

7.62–8.31 (m, 7H, aromatic protons), 8.90 (s, 1H, NH), 9.42 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 124.1, 125.8, 126.6, 128.6, 129.8, 130.3, 130.7, 133.2, 134.8, 135.2, 139.3, 149.0, 160.5 ppm. Anal. Calcd for C15H9Cl2N3: C, 59.62; H, 3.00;

*3.2.8 7-Chloro-2-(3-chlorophenyl)-3,4-dihydroimidazo[4,5-b]indole (4h)*

(m, 8H, aromatic protons), 8.97 (s, 1H, NH), 9.67 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 122.3, 123.6, 125.2, 127.9, 128.4, 129.7, 130.4, 134.4, 134.5, 135.2, 139.0, 147.6, 161.7 ppm. Anal. Calcd for C15H10N4O2: C, 64.70; H, 3.63; N,

*3.2.6 7-Chloro-2-(3-nitrophenyl)-3,4-dihydroimidazo[4,5-b]indole (4f)*

*3.2.7 2-(3-Chlorophenyl)-3,4-dihydroimidazo[4,5-b]indole (4g)*

(m, 7H, aromatic protons), 8.96 (s, 1H, NH), 9.50 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 123.4, 123.8, 124.8, 127.1, 128.0, 128.6, 129.4, 133.9, 134.1, 134.4, 139.7, 148.7, 150.4, 160.6 ppm. Anal. Calcd for C15H9ClN4O2: C, 57.60; H, 2.91;

*3.2.4 7-Chloro-2-(2-nitrophenyl)-3,4-dihydroimidazo[4,5-b]indole (4d)*

*3.2.5 2-(3-Nitrophenyl)-3,4-dihydroimidazo[4,5-b]indole (4e)*

. **1H NMR (300 MHz, DMSO) δ:** 7.61–

. **1H NMR (300 MHz, CDCl3) δ:** 7.66–8.36

. **1H NMR (300 MHz, DMSO) δ:** 7.58–8.55

. **1H NMR (300 MHz, DMSO) δ:** 7.77–8.83

. **1H NMR (300 MHz, DMSO)** 

. **1H NMR (300 MHz, CDCl3) δ:**

**64**

Brownsolid, **IR (KBr) υ:** 3362, 3255, 3015, 2882, 1669, 1620, 1565, 1482, 1375, 1235, 1140, 1026, 890, 777, 663, 526 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 7.48–8.58 (m, 8H, aromatic protons), 9.45 (s, 1H, NH), 10.16 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 123.3, 127.8, 127.9, 128.7, 129.7, 134.9, 135.6, 136.2, 149.7, 161.3 ppm. Anal. Calcd for C15H10ClN3: C, 67.30; H, 3.77; N, 15.70 Found C, 67.31; H, 3.75; N, 15.73.

#### *3.2.10 7-Chloro-2-(4-chlorophenyl)-3,4-dihydroimidazo[4,5-b]indole (4j)*

Brownsolid, **IR (KBr) υ:** 3386, 3233, 3047, 2960, 1657, 1612, 1558, 1435, 1348, 1282, 1153, 1019, 871, 742, 654, 552 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 7.46–8.54 (m, 7H, aromatic protons), 8.99 (s, 1H, NH), 9.35 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ**: 123.9, 125.8, 128.8, 129.8, 130.3, 133.0, 135.2, 136.0, 137.1, 149.1, 159.5 ppm. Anal. Calcd for C15H9Cl2N3: C, 59.62; H, 3.00; N, 13.91 Found C, 59.55; H, 3.10; N, 13.90.

#### *3.2.11 2-(4-Methoxyphenyl)-3,4-dihydroimidazo[4,5-b]indole (4k)*

Brownsolid, **IR (KBr) υ:** 3351, 3138, 3001, 2944, 2881, 1667, 1619, 1575, 1450, 1371, 1284, 1157, 1021, 863, 743, 654, 534 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, DMSO) δ:** 4.00 (s, 3H, CH3), 7.26–8.69 (m, 9H, aromatic protons and 1H, NH), 9.72 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 56.9, 122.2, 123.2, 125.9, 127.7, 127.4, 127.9, 128.7, 129.0, 129.6, 130.7, 131.2, 131.4, 131.5, 138.5, 139.7, 140.1, 143.9, 145.8, 154.6 ppm. Anal. Calcd for C16H13N3O: C, 72.99; H, 4.98; N, 15.96 Found C, 72.91; H, 5.04; N, 15.95.

#### *3.2.12 7-Chloro-2-(4-methoxyphenyl)-3,4-dihydroimidazo[4,5-b]indole (4l)*

Brownsolid, **IR (KBr) υ:** 3370, 3259, 2991, 2911, 1675, 1614, 1558, 1480, 1436 1377, 1291, 1186, 1049, 869, 745, 651, 522 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 3.61 (s, 3H, CH3), 7.44–8.47 (m, 8H, aromatic protons), 8.58 (s, 1H, NH), 9.36 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 61.8, 122.16, 122.29, 124.0, 125.3, 126.6, 130.1, 130.4, 132.3, 133.9, 135.5, 138.5, 148.1, 148.2, 157.8 ppm. Anal. Calcd for C16H12ClN3O: C, 64.54; H, 4.06; N, 14.11 Found C, 64.70; H, 4.00; N, 14.10.

#### *3.2.13 1-(2-(3-Nitrophenyl)imidazo[4,5-b]indol-4(3H)-yl)ethanone (4m)*

Brownsolid, **IR (KBr) υ:** 3389, 3266, 2978, 2935, 1694, 1645, 1616, 1571, 1467, 1346, 1224, 1133, 1021, 823, 744, 641, 572 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 1.91 (s, 3H, CH3), 7.22–8.51 (m, 8H, aromatic protons), 9.40 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 23.7, 122.1, 122.4, 123.2, 123.5, 124.8, 127.2, 127.4, 127.6, 128.2, 129.7, 130.1, 130.9, 133.0, 134.1, 134.4, 135.6, 138.0, 141.0, 148.7, 150.4, 160.3, 172.2 ppm. Anal. Calcd for C17H12N4O3: C, 63.75; H, 3.78; N, 17.49 Found C, 63.68; H, 3.88; N, 17.52.

#### *3.2.14 1-(2-(3-Chlorophenyl)imidazo[4,5-b]indol-4(3H)-yl)ethanone (4n)*

Brownsolid, **IR (KBr) υ:** 3367, 3215, 2947, 2923, 1692, 1662 1607, 1580, 1477, 1359, 1272, 1144, 1042, 807, 735, 653, 546 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 1.25 (s, 3H, CH3), 7.34–8.11 (m, 8H, aromatic protons), 9.36 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 23.6, 122.5, 124.1, 125.3, 126.6, 130.1, 130.4, 130.7,

132.3, 133.9, 134.6, 135.5, 138.5, 148.1, 148.2, 157.8, 160.9, 166.2 ppm. Anal. Calcd for C17H12ClN3O: C, 65.92; H, 3.90; N, 13.57 Found C, 66.01; H, 3.95; N, 13.47.

### *3.2.15 1-(2-(4-Chlorophenyl)imidazo[4,5-b]indol-4(3H)-yl)ethanone (4o)*

Brownsolid, **IR (KBr) υ:** 3350, 3285, 3011, 2935, 1685, 1654 1611, 1572, 1485, 1455, 1343, 1284, 1132, 1062, 899, 783, 659, 531 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 1.66 (s, 3H, CH3), 7.35–8.12 (m, 8H, aromatic protons), 9.37 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 23.5, 123.3, 125.6, 127.2, 128.1, 128.4, 128.7, 129.0, 129.2, 129.5, 133.1, 134.3, 134.6, 134.7, 136.4, 137.0, 142.0, 150.5, 160.2, 160.9 ppm. Anal. Calcd for C17H12ClN3O: C, 65.92; H, 3.90; N, 13.57 Found C, 65.99; H, 3.93; N, 13.54.

#### *3.2.16 4-Ethyl-2-(2-nitrophenyl)-3,4-dihydroimidazo[4,5-b]indole (4p)*

Brownsolid, **IR (KBr) υ:** 3416, 3199, 3012, 2999, 2942, 2872, 1654, 1607, 1561, 1441, 1453 1351, 1283, 1192, 1021, 861, 741, 657, 526 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, DMSO) δ:** 1.41–1.45 (t, *J* = 6.6, 3H, CH3), 4.38–4.45 (q, *J* = 6.9, 2H, CH2), 7.53–8.63 (m, 8H, aromatic protons), 9.63 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 12.5, 24.9, 122.1, 122.8, 123.1, 124.6, 127.5, 127.8, 130.2, 130.4, 130.7, 133.5, 134.4, 137.7, 135.4, 136.4, 137.5, 140.7, 148.3, 149.7, 159.9 ppm. Anal. Calcd for C17H14N4O2: C, 66.66; H, 4.61; N, 18.29 Found C, 66.74; H, 4.65; N, 18.20.

#### *3.2.17 2-(3-Nitrophenyl)-4-propyl-3,4-dihydroimidazo[4,5-b]indole (4q)*

Brownsolid, **IR (KBr) υ:** 3400, 3301, 3221, 3135, 3009, 2951, 2912, 2865, 1664, 1616, 1571, 1478, 1422, 1371, 1271, 1181, 1037, 873, 739, 649, 536 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, CDCl3) δ:** 1.05–1.10 (t, *J* = 6.9, 3H, CH3), 1.70–1.82 (m, 2H, CH2), 3.19–3.24 (t, *J* = 6.6, 2H, CH2), 7.47–8.41 (m, 8H, aromatic protons), 8.94 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, CDCl3) δ:** 10.1, 21.3, 44.0, 121.5, 124.2, 125.2, 125.5, 125.6, 129.3, 136.1, 136.7, 140.5, 150.9, 159.3 ppm. Anal. Calcd for C18H16N4O2 C, 67.49; H, 5.03; N, 17.49 Found C, 67.44; H, 5.10; N, 17.52.

#### *3.2.18 Ethyl 2-(2-(2-nitrophenyl)imidazo[4,5-b]indol-4(3H)-yl)acetate (4r)*

Brownsolid, **IR (KBr) υ:** 3389, 3255, 3129, 3116, 3027, 2969, 2913, 2847, 1735, 1657, 1618, 1569, 1435, 1353, 1264, 1158, 1049, 854, 751, 651, 546 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, DMSO) δ:** 1.22–1.27 (t, *J* = 7.2, 3H, CH3), 4.19–4.26 (q, *J* = 6.9, 2H, CH2), 5.32 (s, 2H, CH2), 7.37–8.28 (m, 8H, aromatic protons), 9.63 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 15.0, 52.6, 65.1, 122.3, 123.6, 125.2, 127.9, 128.4, 130.5, 134.0, 135.2, 139.0, 148.3, 149.6, 161.7, 171.0 ppm. Anal. Calcd for C19H16N4O4: C, 62.63; H, 4.43; N, 15.38 Found C, 62.71; H, 4.51; N, 15.30.

#### *3.2.19 7-Methyl-2-phenyl-3,4-dihydroimidazo[4,5-b]indole (4 s)*

Brownish whitesolid, **IR (KBr) υ:** 3398, 3242, 2963, 2931, 1648, 1607, 1559, 1451, 1311, 1232, 1142, 1027, 813, 741, 655, 534 cm<sup>−</sup><sup>1</sup> . **1H NMR (300 MHz, DMSO) δ:** 2.22 (s, 3H, CH3), 7.55–8.57 (m, 8H, aromatic protons), 9.69 (s, 1H, NH), 10.10 (s, 1H, NH) ppm. **13C NMR (75.45 MHz, DMSO) δ:** 23.9, 122.9, 123.1, 127.7, 128.5, 129.6, 130.2, 130.7, 131.3, 133.3, 136.8, 146.3, 154.1, 161.2 ppm. Anal. Calcd for C16H13N3: C, 77.71; H, 5.30; N, 16.99 Found C, 77.64; H, 5.34; N, 17.02.

**67**

*Eco-Friendly and Facile Synthesis of Substituted Imidazoles via Nano Zirconia Catalyzed…*

ZrO2 nanoparticles have been synthesized and a novel synthetic route has been developed for the multicomponent reaction of isatin derivatives with ammonium acetate and substituted aromatic aldehydes using ZrO2 nanoparticles under solventfree conditions. The yields of the products obtained were up to 93% at 110°C. The advantage of the proposed method is its facile reaction conditions; the product can be isolated very easily without the use of column chromatography and the catalyst can be recycled. The simplicity of the presented protocol makes it an interesting alternative to other approaches. The obtained catalyst is expected to contribute to the development of environmentally benign methods and forms a part of nanomaterial chemistry.

*DOI: http://dx.doi.org/10.5772/intechopen.82720*

NMR spectra of compound **4a**

**4. Conclusion**

**A. Appendix**

*Eco-Friendly and Facile Synthesis of Substituted Imidazoles via Nano Zirconia Catalyzed… DOI: http://dx.doi.org/10.5772/intechopen.82720*
