c) 4-Amino-6-methyl-N 1 -phenyl-1H-pyrazolo[3,4-d]pyrimidine 4c Yield 70 %; mp 160 °C; IR (cm−1); ν NH2 3090, 3320; ν C=N 1597, 1638, 1663; RMN 1H (δ ppm,

DMSO): 2.65 (3H, s, CH3), 4.28 (2H, s, NH2), 7.28 (1H, t, J = 7.3 Hz, ArH4), 7.56 (2H, t, J = 7.3 Hz, ArH3 and ArH5), 8.19 (2H, d, J = 7.3 Hz, ArH2 and ArH6), 8.29 (1H, s, H6); RMN13C (δ ppm, DMSO): 14.44 (CH3), 100.24 (C-3a), Carom 120.24 (C-2′ and C-6′), 124.67 (C-4′), 129.16 (C-3′ and C-5′), 138.8 (C-3), 142.79 HDAC inhibitors cancer (C-1′); C3 154.14 (C-7a), 156.51 (C-4),158.58 (C-6); HRMS Calcd. for C12H11N5 : https://www.selleckchem.com/products/DAPT-GSI-IX.html 225.1014, found: 225.1016.   7-Imino-N 1-phenyl-1,7-dihydropyrazolo[3′,4′:4,5]pyrimido[1,6-a]pyrimidine 5a–e A mixture of compound 4 (1.0 mmol), ketene ethoxymethylene compounds 1 or

ethyl-2-cyano-3-ethoxyalkyl-2-enoate (1.0 mmol) and a catalytic amount of acetic acid was refluxed for 2 h in 10 ml ethanol. The formed precipitate was filtered, washed by diethyl ether, dried and recrystallized from ethanol to give compound 5 in good yield. a) 6-Cyano-7-imino-3-methyl-N 1 -phenyl-1,7-dihydropyrazolo[3′,4′:4,5]pyrimido[1,6-a]pyrimidine 5a Yield 68 %; mp 290 °C; IR (cm−1); ν NH 3356; ν C≡N 2212;

ν C=N 1534, Reverse transcriptase 1554, 1587; RMN 1H (δ ppm, DMSO): 2.51 (3H, s, CH3); 7.38 (1H, t, J = 7.3 Hz, ArH4); 7.53 (2H, t, J = 7.3 Hz, ArH3 and ArH5); 7.71 (2H, d, J = 7.3 Hz, ArH2 and ArH6); 8.02 (1H, s, H5); 8.38 (1H, s, H9); 8.66 (1H, s, NH); RMN13C (δ ppm, DMSO): 14.64 (CH3); 91.81 (C-6); 105.88 (C-3a); 116.24 (CN); Carom 120.46 (C-2′ and C-6′), 124.17 (C-4′), 129.27 (C-3′ and C-5′), 137.89 (C-1′),143.42 (C-10a), 149.71 (C-3),159.61 (C-5),161.88 (C-9), 162.15 (C-4a); 163.43 (C-7); HRMS Calcd. for C16H11N7 :301.1076, found: 301.1051.   b) 6-Cyano-7-imino-3,5-dimethyl-N 1 -phenyl-1, 7-dihydropyrazolo[3′, 4′:4, 5]pyrimido[1, 6-a]pyrimidine 5b Yield 54 %; mp 182 °C; IR (cm−1): ν NH 3324; ν C≡N 2230; ν C=N 1509, 1562, 1586; RMN 1H (δ ppm, DMSO): 2.50 (3H, s, CH3), 2.64 (3H, s, CH3); 7.26 (1H, t, J = 7.3 Hz, ArH4); 7.51 (2H, t, J = 7.3 Hz, ArH3 and ArH5); 7.54 (2H, d, J = 7.3 Hz, ArH2 and ArH6); 8.19 (1H, s, H9); 8.27 (1H, s, NH); RMN13C (δ ppm, DMSO): 14.42 (CH3); 21.00 (CH3); 87.23 (C-6); 100.25 (C-3a); 109.00 (CN); 120.22 (C-2′ and C-6′), 125.51 (C-4′), 128.98 (C-3′ and C-5′), 138.89 (C-1′); 142.79 (C-10a); 154.17 (C-3), 156.49 (C-5), 164.59 (C-9), 165.71 (C-4a), 167.94 (C-7); HRMS Calcd. for C17H13N7 : 315.1232, found: 315.1214.