Visible Light Photoredox-Catalyzed Synthesis of Quinazolinone Derivatives and their cytotoxicity

Received: 21-Oct-2019 Accepted Date: Jul 08, 2020 ; Published: 28-Aug-2020

Introduction

Quinazolinone derivatives are important bioactive nitrogen-containing heterocycles and are present in several natural products such as vitamins, alkaloids, etc. Due to their diverse pharmacological and biological activities [1] quinazolinone scaffolds are very important in the synthesis of various biologically active compounds. Recently, these compounds are reported to exhibit as gene associated peptide and vasopressin receptor antagonists [2,3]. Febrifugine (I), a quinazolinone alkaloid was first isolated from the Chinese herb Dichoria febrifuges. It has important biological properties such as antimalarial [4], anticancer [5]and anti-inflammatory [6,7]. DPC-961 (II) and SM-15811 (III) (Figure 1) are compounds having quinazolinone ring and are known to exhibit 2nd generation anti-HIV activity, ion exchanger properties and also used to treat heart diseases and luotonine A showed excellent cytotoxicity towards the murine leukemia and rutaecarpine used extensively as a remedy for headache, cholera, and dysentery. Considering the significance of quinazolinones from an application perspective, although a number of methods have been made to construct the quinazolinones [8], these routes mainly rely on using anthranilic acid or its derivatives as starting materials. Generally, metal catalysed reductive cyclization of anthranilamide with ketones, aldehydes and isatins by the alternative approaches used for the synthesis of substituted quinazolinones [9].

Figure 1: Biologically important quinazolinones

However, these methods have some eco-friendly aspects but these methods are associated with several drawbacks such as usage of hazardous organic solvents, reagents, metal catalysts, harsh reaction conditions and low yields. So, there is a need for the development of green, sustainable, efficient and safety and alternative method for the synthesis of quinazolinones via visible light promoted metal free photocatalyst in environmental aspect was highly desirable.

In the present scenario, visible light photo redox catalysis has fascinated the chemists in the forefront of the organic synthesis due to its attractive features like mild reaction conditions, safe, cheap, abundant and renewable energy source [10]. It is a dominant tool to complete novel organic chemical transformations through single-electron-transfer pathway. Continuing our efforts towards the synthesis of heterocyclic scaffolds [11] herein, we developed a visible light driven environmentally benign process for the synthesis of quinazolinones from readily available 2-aminobenzamide and isatins at room temperature under air by using organic dye such as Rose Bengal as a recyclable photocatalyst.

Materials and Methods

All chemicals, reagents were purchased from the commercial sources and were used without further purification. Reactions were monitored by TLC on silica gel glass plate containing 60 GF-254, and visualization was done by UV light and iodine vapour. 1H and ¹³C NMR spectra were recorded on Bruker UXNMR/XWIN-NMR (300 MHz) or Innova Varian-VXR-unity (400 MHz, 500 MHz) instruments. Chemical shifts were expressed in parts per million (in ppm) downfield from TMS expressed as internal standard and coupling constants are expressed in Hz. ¹H NMR spectral data were reported in the following order: multiplicity (s: singlet; brs: broad singlet; d: doublet; dd: doublet of doublets; t: triplet; m: multiplet), coupling constants in Hz, and number of protons. ESI mass spectra were recorded on a Micromass Quattro LC using ESI+ software with capillary voltage 3.98 kV and an ESI mode positive ion trap detector. High resolution mass spectra were recorded on a QSTAR XL Hybrid MS-MS mass spectrometer. Melting points were determined with an electro thermal digital melting point apparatus IA9100 and are uncorrected.

General reaction procedure for the preparation of compounds (3a-3t)

All the reactions were performed using the following procedure.

To the solution of 2-aminobenzamide (1) (1 mmol) in ethanol add substituted isatin (2) (1 mmol) and Rose Bengal (2 mol%), under the visible light (15 W) setup at room temperature for 2 h, appearance of precipitate indicates the product formation and which was also monitored by the TLC. The solvent was removed by the rota vacuum then purified by the column chromatography to offered quinazolinones in good to excellent yields.

1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3a)

Dirty white solid; 87% yield; mp 290°C-295°C; ¹H NMR (300 MHz, DMSO-d₆): δ 9.76 (s, 1H), 7.80 (d, J=7.9 Hz, 1H), 7.52 (d, J=7.4 Hz, 1H), 7.29-7.21 (m, 2H), 7.03 (t, J=7.4 Hz, 2H), 6.85 (d, J=8.2 Hz, 1H), 6.76 (t, J=7.6 Hz, 1H), 6.67 (d, J=8.1 Hz, 1H), 6.15 (bs, 1H); ¹³C NMR (75 MHz, DMSO-d₆): δ 175.79, 164.14, 146.53, 141.88, 132.98, 130.38, 129.18, 126.73, 124.94, 121.93117.05, 114.07, 113.77, 109.96, 70.84; IR (KBr pellets) υ: 3363, 3339, 3179, 3050, 1730, 1706, 1663, 1620, 1509, 1483, 1470, 1359, 1324, 1185, 748 cm^-1; ESI-MS : m/z=266 (M+H) +; HRMS (ESI) m/z for C₁₅H₁₂O₂N₃ calculated m/z: 266.0924, found m/z: 266.0922 (M+H) +.
5-chloro-1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3b)

White solid; 80% yield; mp 289°C-294°C; ¹H NMR (300 MHz, DMSO-d₆): δ 9.98 (s, 1H), 7.76 (t, J=7.6 Hz, 2H), 7.23 (s, 2H), 6.96 (t, J=7.2 Hz, 1H), 6.82-6.58 (m, 4H) ; ¹³C NMR (75 MHz, DMSO-d₆): ¹³C NMR (75 MHz, DMSO-d₆): δ 175.80, 164.10, 145.72, 141.31, 139.09, 133.55, 133.28, 130.99, 127.05, 117.82, 113.84, 112.42, 83.96, 70.76; IR (KBr pellets) υ: 3252, 1731, 1660, 1651, 1613, 1514, 1504, 1483, 1440, 1359, 1268, 1190, 753, 694 cm^-1; ESI-MS: m/z=300 (M+H)+; HRMS (ESI) m/z for C₁₅H₁₁O₂N₃Cl calculated m/z: 300.0534, found m/z: 300.0534 (M+H)+.

5-bromo-1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3c)

Light red solid; 77% yield; mp 280°C-285°C; ¹H NMR (300 MHz, DMSO-d₆): δ 10.02 (s, 1H), 7.79 (d, J=7.55 Hz, 1H), 7.61 (d, J=1.70 Hz, 1H), 7.48-7.51 (m, 1H), 7.40 (dd, J=1.88 & 8.30 Hz, 1H), 7.24 (dt, J=1.51 & 8.30 Hz, 1H), 6.74-6.78 (m, 2H), 6.68 (d, J=7.93 Hz, 1H), 6.43 (s, 1H); ¹³C NMR (75 MHz, DMSO-d₆): δ 175.28, 163.92, 146.04, 140.91, 133.01, 132.89, 131.17, 127.81, 126.74, 117.32, 113.88, 113.74, 111.67, 70.83; IR (KBr pellets) υ:1731, 1660, 1614, 1513, 1482, 1434, 1358, 1302, 1268, 1189, 1145, 1122, 817, 752, 628, 566, 538 cm^-1; ESI-MS: m/z=343 (M)+; HRMS (ESI) m/z for C₁₅H₁₁O₂N₃ Br calculated m/z: 343.0029, found m/z: 343.0030 (M)+.

5-flouoro-1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3d)

White solid; 79% yield; mp 285-287°C; ¹H NMR (300 MHz, DMSO-d₆): δ 9.98 (s, 1H), 7.78 (m, 2H), 7.23 (bs, 2H), 7.01 (t, J =7.36 Hz, 1H), 6.81-6.66 (m, 3H), 6.58 (s, 1H); ¹³C NMR (75 MHz, DMSO-d₆): δ 175.80, 164.10, 146.14, 137.63, 133.09, 130.43, 126.80, 117.40, 116.80, 113.94, 113.83, 112.67, 110.70, 71.12; IR (KBr pellets) υ: 3282, 1741, 1661, 1632, 1613, 1520, 1185, 1146, 1124, 1042, 817, 758, 710, 693, 636, 616 cm^-1; ESI-MS: m/z=284 (M+H)+; HRMS (ESI) m/z for C₁₅H₁₁O₂N₃F calculated m/z: 284.0829, found m/z: 284.0831 (M+H)+.

5-iodo-1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3e)

White solid; 80%yield; mp 240-245°C; 1HNMR(300MHz, DMSO-d₆): 10.04 (s, 1H), 7.77 (d, J=8.6 Hz, 3H), 7.58 (d, J=7.9 Hz, 1H), 7.25 (t, J=7.55 Hz, 1H), 6.76-6.64 (m, 4H); ¹³C NMR (75 MHz, DMSO-d₆): δ 175.02, 164.18, 145.72, 141.31, 139.09, 133.55, 133.28, 130.99, 127.05, 117.82, 113.84, 112.42, 83.96, 70.76; IR (KBr pellets) υ: 3282, 1741, 1661, 1613, 1520, 1484, 1425, 1371, 1335, 1299, 1265, 1185, 1146, 1124, 1042, 817, 758, 636, 616 cm^-1; ESI-MS: m/z=390 (M)+; HRMS (ESI) m/z for C₁₅H₁₁O₂N₃I calculated m/z: 391.9890, found m/z: 391.9892 (M)+.

5-methyl-1H-spiro[indoline-3,2-quinazoline]-2,4’(3’H)-dione (3f)

White solid; 85% yield; mp 150-155°C; ¹H NMR (300 MHz, DMSO-d₆): δ 9.81 (s, 1H), 7.75 (d, J=7.17 Hz, 1H), 7.40 (brs, 1H), 7.34 (s, 1H), 7.22 (t, J=8.30 Hz, 1H), 7.07 (d, J=7.55 Hz, 1H), 6.65-6.80 (m, 3H), 6.49 (s, 1H), 2.30 (s, 3H); ¹³C NMR (75 MHz, DMSO-d₆ ): δ 175.77, 164.19, 146.40, 139.20, 132.94, 131.16, 130.62, 129.00, 126.75, 125.49, 117.06, 113.97, 113.72, 109.73, 70.92, 20.48; IR (KBr pellets) υ: 3314, 2922, 2853, 1706, 1655, 1613, 1513, 1489, 1357, 1329, 1270, 1207, 1154, 811, 751, 698 cm^-1; ESI-MS: m/z=280 (M+H); HRMS (ESI) m/z for C₁₆H₁₄O₂N₃ calculated m/z: 280.1080, found m/z: 280.1081 (M+H) +.

5-nitro-1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3g)

White solid; 84% yield; mp 230-235°C; ¹H NMR (300 MHz, DMSO-d₆): δ 10.85 (s, 1H), 8.19-8.40 (m, 3H), 7.71 (d, J=7.17 Hz, 1H), 7.14 (s, 1H), 7.24 (t, J=8.49 Hz, 1H), 7.00 (d, J=8.68 Hz, 1H), 6.75 (t, J=7.55 Hz, 1H), 6.67 (d, J=7.93 Hz, 1H); ¹³C NMR (75 MHz, DMSO-d₆): δ 176.04, 163.82, 148.22, 145.90, 142.41, 133.19, 130.02, 127.10, 126.81, 120.62, 117.62, 113.90, 109.99, 70.56; IR (KBr pellets) υ: 3342, 3021, 2860, 1727, 1649, 1616, 1522, 1482, 1405, 1339, 1296, 1252, 1229, 1189, 1143, 1121, 1085, 837, 746, 733, 690, 635, 550 cm^-1; ESI-MS: m/z=311 (M+H)+; HRMS (ESI) m/z for C₁₅H₁₁O₄N₄ calculated m/z: 311.0774, found m/z: 311.0775 (M+H)+.

1-benzyl-5-chloro-1-H-spiro[indoline-3,2-quinazoline]-2,4(3H)-dione (3h)

White solid; 79% yield; mp 150°C-155°C; ¹H NMR (DMSO-d₆, 300 MHz) δ: 8.1 (s, 1H), 7.8 (d, J=7.9 Hz, 1H), 7.6 (s, 1H), 7.55 (t, J=8.1 Hz, 2H), 6.9 (s, 1H ), 6.77-6.68 (m, 4H), 6.5 (bs, 1H), 6.0 (bs, 1H), 4.9 (s, 1H), 4.8 (s, 2H, ), 3.8 (d, 1H); ¹³C NMR (75 MHz, DMSO-d₆): δ 145.16, 141.26, 133.8, 133.4, 130.75, 129.4, 126.09, 123.8, 121.6, 116.4, 115.41, 113.70, 107.65, 69.27, 41.89; IR (KBr pellets, υ: 3758, 3713, 3707, 3685, 3644, 3625, 3583, 3270, 2923, 2357, 1737, 1731, 1715, 1666, 1660, 1650, 1644, 1633, 1613, 1514, 1504, 1494, 1485 1434, 1336 cm^-1; ESI-MS m/z: 389 (M+); HRMS (ESI) m/z for C₂₂H₁₇C_lN₃O₂ calculated m/z: 390.1003, found m/z: 390.1004 (M+H)+.

5-methoxy-1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3i)

White solid; 85% yield; mp 270°C-275°C; ¹H NMR (300 MHz, DMSO-d₆): δ 9.74 (s, 1H), 7.79 (d, J=7.8 Hz, 1H), 7.5 (s, 1H), 7.45 (bs, 1H), 7.1 (s, 1H ), 6.81-6.45 (m, 4H ), 6.45 (s, 1H), 3.75 (s, 3H); ¹³C NMR (75 MHz, DMSO-d₆): δ 175.8, 163.94, 155.10, 154.46, 146.58, 134.95, 132.87, 130.34, 128.28, 127.81, 126.64, 123.55, 116.93, 116.58, 115.37, 144.08, 113.69, 111.36, 110.39, 108.35, 71.18, 55.29; IR (KBr pellets) υ: 3314, 3215, 2924, 1719, 1648, 1609, 1513, 1485, 1440, 1357, 1296, 1270, 1234, 1162, 1043, 1024, 824, 794, 756, 715, 698, 672, 621, 578 cm^-1; ESI-MS : m/z=296 (M+H) +; HRMS (ESI) m/z for C₁₆H₁₄O₃N₃ calculated m/z : 296.1029, found m/z: 296.1030 (M+H) +.

5,6-dimethyl-1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3j)

White solid; 87% yield; mp 320°C-325°C; ¹H NMR (300 MHz, DMSO-d₆): δ 9.81 (s, 1H), 7.75 (d, J=7.2 Hz, 1H), 7.40 (bs, 1H), 7.34 (s, 1H), 7.22 (t, J=8.30 1H), 7.07 (d, J=7.55 Hz, 1H), 6.80-6.65 (m, 2H), 6.49 (s, 1H), 2.39 (s, 6H); ¹³C NMR (75 MHz, DMSO-d₆ ): δ 175.78, 164.20, 146.41, 139.20, 132.94, 131.16, 130.62, 129.00, 126.75, 125.49, 117.06, 113.97, 113.72, 109.73, 70.92, 20.48; IR (KBr pellets) υ: 3311, 3301, 2902, 2833, 1706, 1685, 1623, 1513, 1489, 1357, 1329, 1270, 1207, 1154, 811, 751, 698 cm^-1; ESI-MS : m/z=293 (M+H) +; HRMS (ESI) m/z for C₁₇H₁₆O₂N₃ calculated m/z: 294.1237, found m/z: 294.1239 (M+H) +.

1-benzyl-1'H-spiro[indoline-3,2'-quinazoline]-2,4'(3'H)-dione (3k)

White solid; 82% yield; mp 240°C-245°C; ¹H NMR (300 MHz, DMSO-d₆): δ 8.04 (s, 1H), 7.79 (d, J=7.4 Hz, 1H), 7.68 (s, 1H), 7.59 (d, J=8.2 Hz, 1H), 7.12 (t, J=7.2 Hz, 1H), 6.93-6.84 (m, 3H ), 6.77-6.68 (m, 5H), 5.94 (s, 2H ), 4.72 (s, 2H); ¹³C NMR (75 MHz, DMSO-d₆ ): δ 174.05, 171.39.164.31, 149.33, 146.18, 142.32, 134.91, 131.78, 130.43, 128.21, 127.11, 126.86, 124.83, 120.30, 117.44, 114.89, 113.88, 109.01, 107.78, 100.53, 70.65, 42.92; IR (KBr pellets) υ: 3329, 3179, 3054, 2918, 1705, 1667, 1615, 1511, 1489, 1466, 1454, 1362, 1314, 1264, 1175, 1142, 993, 749, 696, 678, 630 cm^-1; ESI-MS : m/z=356 (M+H) +; HRMS (ESI) m/z for C₂₂H₁₈O₂N₃ calculated m/z: 356.1393, found m/z: 356.1395 (M+H) +.

1-(benzo[d][1,3]dioxol-5-ylmethyl)-1H-spiro[indoline-3,2-quinazoline]2,4(3H)-dione (3l)

White solid; 84% yield; mp 260°C-265°C; ¹H NMR (300 MHz, DMSO-d₆): δ 8.01 (s, 1H), 7.79 (d, J=7.6 Hz, 1H), 7.66 (s, 2H ), 7.57 (d, J=7.2 Hz, 1H), 7.48 (d, J=7.3 Hz, 1H), 7.31-6.68 (m, 7H), 5.94 (s, 2H), 4.72 (s, 2H); ¹³C NMR (75 MHz, DMSO-d₆): δ 174.05, 164.22, 147.44, 146.47, 146.28, 142.27, 133.03, 130.38, 128.64, 126.79, 124.75, 122.64, 120.31, 117.31, 114.05, 113.84, 109.16, 107.80, 107.41, 100.57, 70.67, 42.67; IR (KBr pellets) υ: 3193, 3059, 1658, 1670, 1615, 1487, 1467, 1444, 1356, 1272, 1244, 1190, 1174, 1143, 1100, 1036, 743, 695 cm^-1; ESI-MS: m/z=400 (M+H)+; HRMS (ESI) m/z for C₂₃H₁₈O₄N₃ calculated m/z: 400.1291, found m/z: 400.1293 (M+H)+.

1-(benzo[d][1,3]dioxol-5-ylmethyl)-5-chloro-1H-spiro[indoline-3,2-quinazoline]2,4(3H)-dione (3m)

White solid; 79% yield; mp 195°C-200°C; ¹H NMR (300 MHz, DMSO-d₆): δ 8.11 (d, J=7.17 Hz, 1H), 7.68 ( d, J=9.63 Hz, 1H ), 7.52 (t, J=7.93 Hz, 1H ), 7.41-7.25 ( m, 3H ), 6.99 (t, J=6.42 Hz, 2H), 6.85-674 (m, 4H), 6.50 (s, 1H), 5.92 (d, J=7.36, 2H), 4.81 (s, 1H); ¹³C NMR (75 MHz, DMSO-d₆): δ 174.57, 166.34, 145.08, 136.68, 133.49, 131.48, 131.20, 130.37, 127.83, 125.66, 124.99, 123.36, 120.15, 116.69, 116.12, 114.68, 111.76, 111.06, 107.59, 107.05, 100.35, 42.59; IR (KBr pellets) υ: 3272, 1670, 1659, 1651, 1647, 1632, 1614, 1573, 1562, 1551, 1536, 1532, 1513, 1492, 1483, 1470, 1453, 1432, 1415, 1391, 1370, 1335, 1171, 1252, 1123, 1080, 1028, 817, 753 cm^-1; ESI-MS: m/z=434 (M+H)+; HRMS (ESI) m/z for C₂₃H₁₇O₄N₃Cl calculated m/z: 434.0903, found m/z: 434.0905 (M+H)+.

1-(benzo[d][1,3]dioxol-5-ylmethyl)-5-bromo-1H-spiro[indoline-3,2-quinazoline]2,4 (3H)-dione (3n)

White solid; 76% yield; mp 160°C-165°C; ¹H NMR (DMSO-d₆, 300 MHz, ppm) δ: 7.53, (t, J=8.3 Hz, 3H), 7.3 (bs, 1H), 7.20 (t, J=8.3 Hz, 3H), 6.7 ( d, J=7.9 Hz, 3H), 6.62 ( t, J=7.7 Hz, 2H), 5.9 (bs, 4H); ¹³C NMR (75 MHz, DMSO-d₆): δ 171.47, 164.31, 149.33, 146.18, 142.32, 134.91, 133.07, 131.78, 128.26, 127.11, 126.86, 124.83, 122.67, 120.30, 117.44, 116.44, 114.89, 113.88, 133.64, 109.01, 70.65, 42.92; IR (KBr pellets) υ: 3411, 2923, 2853, 1731, 1650, 1585, 1546, 1487, 1452, 1402, 1315, 1257, 1151, 743 cm^-1; ESI-MS m/z: 433 (M+). HRMS (ESI) m/z for C₂₂H₁₇BrO₂N₃ calculated m/z: 434.0498, found m/z: 434.0499 (M+H)+.

7-fluoro-1H-spiro[indoline-3,2’-quinazoline]-2,4’(3’H)-dione (3o)

light white solid; 79% yield; mp 310°C-315°C; ¹H NMR (300 MHz, DMSO-d₆): δ 9.96 (s,1H), 7.78 (d, J=7.5 Hz, 2H), 7.70 (s, 1H), 7.23 (s, 1H) 7.09, 6.99 (t, J=7.36 Hz, 1H), 6.81-6.78 (m, 2H), 6.68 (s, J=7.9 Hz, 1H) 6.58 (s, 1H); ¹³C NMR (75 MHz, DMSO-d₆): δ 175.80, 164.10, 146.14, 137.63, 133.09, 130.43, 126.80, 117.40, 116.80, 113.94, 113.83, 112.67, 110.70, 71.12; IR (KBr pellets) υ: 3326, 3177, 1732, 1614, 1588, 1516, 1486, 1370, 1358, 1314, 1272, 1254, 1203, 1152, 1083, 1033, 902, 736, 686, 661, 603, 578, 527 cm^-1; ESI-MS: m/z=284 (M+H)+; HRMS (ESI) m/z for C₁₅H₁₁O₂N₃F calculated m/z: 284.0829, found m/z: 284.0831 (M+H)+.

1’H-spiro[cyclohexane-1,2’-quinazoline]-4’(3’H)-one (3p)

White solid; 86% yield; mp 235°C-239°C; ¹H NMR (300 MHz, DMSO-d₆) δ 7.80 (s, 1H), 7.25, (s, 1H), 6.85 (d, J=7.93 Hz, 2H ), 5.24 (s, 1H), 2.77 (bs, 1H), 2.17 (s, 2H), 1.82-1.45 (m, 8H); ¹³C NMR (75 MHz, DMSO-d₆): δ 163.69, 145.95, 132.90, 127.12, 116.85, 114.25, 67.67, 36.95, 24.17, 21.00; IR(KBr pellets) υ: 3365, 3169, 3023, 2926, 2852, 1647, 1504, 1482, 1416, 1381, 1323, 1268, 1143, 756 cm^-1; ESI-MS: m/z=217 (M+H)+; HRMS (ESI) m/z for C₁₃H₁₇ON₂ calculated m/z: 217.1335, found m/z: 217.1336 (M+H)+.

6-chloro-1'H-spiro[indoline-3,2'-quinazoline]-2,4'(3'H)-dione (3q)

White solid; 81% yield; mp 284°C-289°C; ¹H NMR (300 MHz, DMSO-d₆): δ 8.79 (s, 1H), 6.51 (d, J=7.82 Hz, 3H), 6.33 (d, J=7.93 Hz, 1H), 5.97 (t, J=8.23 Hz, 1H), 5.51-5.39 (m, 4H); ¹³C NMR (75 MHz, DMSO-d₆): δ 174.46, 163.62, 145.16, 140.78, 138.53, 132.72, 130.42, 126.49, 117.26, 111.86, 83.40, 70.20, 59.20, 19.43, 13.11; IR (KBr pellets) υ: 3256, 1734, 1661, 1651, 1612, 1516, 1505, 1483, 1442, 1358, 1267, 1191, 754, 695 cm^-1; ESI-MS: m/z=300 (M+H)+; HRMS (ESI) m/z for C₁₅H₁₁O₂N₃Cl calculated m/z: 300.0532, found m/z: 300.0534 (M+H)+.

6-bromo-1'H-spiro[indoline-3,2'-quinazoline]-2,4'(3'H)-dione (3r)

Brown solid; 73% yield; mp 275°C-280°C; ¹H NMR (300 MHz, DMSO-d₆): δ 8.77 (s, 1H), 6.47 (t, J=8.68 Hz, 3H), 6.30 (t, J=7.93 Hz, 1H), 5.95 (t, J=7.55 Hz, 1H), 5.49-5.37 (m, 4H); ¹³C NMR (75 MHz, DMSO-d₆): δ 175.85, 165.02, 146.56, 142.15, 139.92, 134.38, 131.82, 127.88, 118.68, 114.67, 113.25, 84.79, 71.59, 60.59, 14.50; IR (KBr pellets) υ: 1735, 1661, 1617, 1514, 1483, 1435, 1358, 1301, 1267, 1187, 1146, 1121, 816, 754, 628, 564, 539 cm^-1; ESI-MS: m/z=343 (M)+; HRMS (ESI) m/z for C₁₅H₁₁O₂N₃Br calculated m/z: 344.0029, found m/z: 343.0031 (M)+.

4-methyl-1'H-spiro[indoline-3,2'-quinazoline]-2,4'(3'H)-dione (3s)

White solid; 76% yield; mp 152-154°C; ¹H NMR (300 MHz, DMSO-d₆): δ 9.98 (s, 2H), 7.57 (t, J=7.55 Hz, 5H), 7.56 (s, 1H), 6.99 (s, 2H), 2.03 (d, J=7.36 Hz, 3H); ¹³C NMR (75 MHz, DMSO-d₆ ): δ 175.24, 163.54, 155.97, 145.59, 137.08, 132.54, 126.25, 116.85, 116.25, 115.94, 113.39, 112.11, 111.79, 110.15, 70.57; IR (KBr pellets) υ: 3317, 2921, 2851, 1708, 1653, 1613, 1514, 1486, 1357, 1328, 1270, 1205, 1151, 817, 755, 698 cm^-1; ESI-MS: m/z=280 (M+H); HRMS (ESI) m/z for C₁₆H₁₄O₂N₃ calculated m/z: 280.1081, found m/z: 280.1083 (M+H) +.

1-(benzo[d][1,3]dioxol-5-ylmethyl)-6-chloro-1'H-spiro[indoline-3,2'-quinazoline]-2,4'(3'H)-dione (3t)

White solid; 79% yield; mp 195°C-200°C; ¹H NMR (300 MHz, DMSO-d₆): δ 8.18 (d, J=7.18 Hz, 1H), 7.78 (s, 1H), 7.61(s, 1H), 7.50-7.35 (m, 3H), 7.11-7.06 (m, 1H), 76.93-6.83 (m, 4H), 6.60 (s, 1H), 6.02 (d, J=7.17 Hz, 2H), 4.96 (s, 2H); ¹³C NMR (75 MHz, DMSO-d₆): δ 166.06, 152.48, 147.05, 144.80, 136.40, 133.22, 130.09, 127.55, 124.72, 119.87, 116.41, 114.40, 110.78, 106.77, 100.07, 42.65; IR (KBr pellets) υ: 3272, 1670, 1659, 1651, 1647, 1632, 1614, 1573, 1562, 1551, 1536, 1532, 1513, 1492, 1483, 1470, 1453, 1432, 1415, 1391, 1370, 1335, 1171, 1252, 1123, 1080, 1028, 817, 753 cm^-1; ESI-MS: m/z=434 (M+H)+; HRMS (ESI) m/z for C₂₃H₁₇O₄N₃Cl calculated m/z: 434.0903, found m/z: 434.0905 (M+H)+.

MTT Assay

The cytotoxicity of these compounds was determined using MTT assay.13 Cancer cells (DU-145, MCF-7, HeLa and A549) were used in this assay. 1×104 cells/well were seeded in 200 μl Dulbecco’s modified Eagle’s medium (DMEM), supplemented with 10% FBS in each well of 96-well micro culture plates and incubated for 24 h at 37°C in a CO₂ incubator. All the derivatives diluted to the desired concentrations (500 nM, 1 μM, 5 μM, 10 μM, 25 μM, 50 μM, 75 μM, 100 μM and 150 μM) in culture medium, were added to the wells with respective vehicle control. Doxorubicin treated cells, in the same concentration range were used as standards. After 48 h of incubation, 10 μl MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) (5 mg/ml) was added to each well and the plates were further incubated for 4 h. Then the supernatant from each well was carefully removed, Formosan crystals were dissolved in 100 μl of DMSO and absorbance at 570 nm wavelength was recorded at a wavelength of 540 nm using an ELx800 micro plate reader (BioTek, USA) [12,13].

Conclusion

In conclusion, a simple, efficient and environmentally benign visible light mediated method for the synthesis of quinazolinone derivatives has been developed by employing Rose Bengal as a recyclable metal free photocatalyst in ethanol. The advantages of this method include its simplicity in operation, use of renewable visible light as an energy source, eco-friendly reactions, higher yields and absence of side products. Using this protocol, a series of twenty compounds has been synthesized and this is a practical and economical method for the development of functionalized quinazolinones. The synthesized compounds were evaluated for their cytotoxic potential on selected human cancer cell lines. Some of these compounds showed IC50 values ranging between 1.13 μM to 1.77 μM against DU-145 cell line.

Acknowledgements

J.K thanks to Vardhaman College of Engineering for providing support.

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