## 2 Materials and Methods
### Synthesis  
General Procedure for the MCR of Compounds **4a-q**  
The mixture of 6-aminopyrimidin-4-one **1** (1 mmol), naphthalene-1,2,4(3\(H\))-trione **2** (1 mmol) and aldehyde **3** (1 mmol), were irradiated for 5-9 min and 200 \({}^{\circ}\)C under solvent-free conditions. Upon completion, monitored by thin-layer chromatography (TLC), the reaction mixture was cooled to room temperature. The solid was further purified by recrystallization from EtOH (95%). _2-methylthio-5-phenyl-5,12-dihydrobenzzo[g]pyrimidinido[4,5-b]quinoline-4,6,11(3\(H\))-trione_ **(4a)**. 80%. m.p. \(>\) 300 \({}^{\circ}\)C. IR (KBr, \(\upsilon\) cm\({}^{-1}\)), 3398 (N-H st), 2689 (CH\({}_{3}\) st), 1652, 1630 (C=O st). \({}^{1}\)H NMR (400 MHz, DMSO-\(d_{6}\)) \(\delta\) (ppm): 2.55 (s, 3H, SCH\({}_{3}\)), 5.25 (s, 1H, CH), 7.11 (t, \(J\) = 6.78 Hz, 1H, Hp), 7.21 (t, \(J\) = 7.28 Hz, 2H, Hm), 7.30 (d, \(J\) = 7.78 Hz, 2H, Ho), 7.76-7.84 (m, 2H, H8, Hp), 7.90 (d, \(J\) = 7.28 Hz, 1H, H7), 8.03 (d, \(J\) = 7.03 Hz, 1H, H10), 9.60 (s, 1H, NH), 12.49 (s, 1H, NH). \({}^{13}\)C NMR \(\delta\) (ppm): 12.7 (SCH\({}_{3}\)), 54.3 (C5), 117.4 (C4a), 124.5 (Cp), 125.3 (Co), 125.6 (C10), 127.3 (C_m_), 127.9 (C7), 130.3, 131.8 (C10a), 133.2 (C8), 134.6 (C9), 139.3 (C5a), 145.0 (Ci), 179.1 (C=O), 181.6 (C=O). MS: (70 eV) \(m/z\) = 401 (16, M\({}^{+}\)), 325 (19), 324 (100), 276 (13). Anal. Calcd. for C\({}_{22}\)H\({}_{15}\)N\({}_{3}\)O\({}_{5}\)S C, 65.82; H, 3.77; N, 10.47; found C, 65.85; H, 3.80; N, 10.45. _2-methylthio-5-(4-methylphenyl)-5,12-dihydrobenzo[g]pyrimidine[4,5-b]quinoline-4,6,11(3\(H\))-trione_ **(4b)**. 80%. m.p. \(>\) 300 \({}^{\circ}\)C (dec). IR (KBr, \(\upsilon\) cm\({}^{-1}\)), 3395 (N-H st), 2929 (CH\({}_{3}\) st), 1651 (C=O st). \({}^{1}\)H NMR (400 MHz, DMSO-\(d_{6}\)) \(\delta\) (ppm): 2.18 (s, 3H, CH\({}_{3}\)), 2.55 (s, 3H, SCH\({}_{3}\)), 5.21 (s, 1H, CH), 7.00 (d, \(J\) = 8.03 Hz, 2H, Hm), 7.16 (d, \(J\) = 8.03 Hz, 2H, H0), 7.77-7.84 (m, 2H, H8, Hp), 7.90 (d, \(J\) = 7.53 Hz, 1H, H7), 8.02 (d, \(J\) = 7.03 Hz, 1H, H10), 9.58 (s, 1H, NH), 12.51 (s, 1H, NH). \({}^{13}\)C NMR \(\delta\) (ppm): 12.7 (\(p\)-CH\({}_{3}\)), 20.5 (SCH\({}_{3}\)), 34.1 (C5), 117.7 (C4a), 125.6 (C10), 125.9 (C7), 127.7 (Co), 128.7 (Cm), 130.3 (Ca), 131.9 (C10a), 133.3 (C8), 134.8 (C9), 135.6 (C2), 139.2 (C5a), 142.2 (Ci), 179.2 (C=O), 181.7 (C=O). MS: (70 eV) \(m/z\) (%) = 415 (30, M\({}^{+}\)), 324 (100), 276 (14). Anal. Calcd. for C\({}_{23}\)H\({}_{17}\)N\({}_{3}\)O\({}_{5}\)S C, 66.49; H, 4.12; N, 10.11; found C, 66.48; H, 4.13; N, 10.14. _5-(4-methoxyphenyl)-2-methylthio-5,12-dihydrobenzo[g]pyrimidine[4,5-b]quinoline-4,6,11(3\(H\))-trione_ **(4c)**. Yellow crystalline solid, 80%. m.p. \(>\) 300 \({}^{\circ}\)C (dec). IR (KBr, \(\upsilon\) cm\({}^{-1}\)), 3272 (N-H st), 2841 (CH\({}_{3}\) st), 1674, 1650 (C=O st). \({}^{1}\)H NMR (400 MHz, DMSO-\(d_{6}\)) \(\delta\) (ppm): 2.55 (s, 3H, SCH\({}_{3}\)), 3.65 (s, 3H, OCH\({}_{3}\)), 5.18 (s, 1H, H5), 6.76 (d, \(J\) = 8.79 Hz, 2H, H\(\omega\)), 7.18 (d, \(J\) = 8.79 Hz, 2H, H\(\omega\)), 7.77-7.85 (m, 2H, H8, Hp), 7.90 (d, \(J\) = 7.53 Hz,1H, H7), 8.02 (d, \(J\) =7.03 Hz, 1H, H10), 9.60 (s, 1H, H12), 12.52 (s, 1H, H3). \({}^{13}\)C NMR \(\delta\) (ppm): 12.7 (SCH\({}_{3}\)), 34.0 (OCH\({}_{3}\)), 55.0 (C5), 114.0 (Co), 129.0 (Cp), 158.0 (C=O). MS: (70 eV) \(m/z\) = 431 (61, M\({}^{+}\)), 325 (19), 324 (100), 276 (18), 248 (12). Anal. Calcd. for C\({}_{23}\)H\({}_{17}\)N\({}_{3}\)O\({}_{4}\)S C, 64.03; H, 3.97; N, 9.74; found C, 64.02; H, 4.01; N, 9.78. _2-methylthio-5-(3,4,5-trimethoxyphenyl)-5,12-dihydrobenzo[g]pyrimidine[4,5-b]quinoline-4,6,11(3\(H\))-trione_ **(4d)**. 80%. m.p. \(265\)\({}^{\circ}\)C. IR (KBr, \(\upsilon\) cm\({}^{-1}\)), 3264 (N-H st), 2933 (CH\({}_{3}\) st), 1656 (C=O st).