Step 1—Synthesis of N-methyl-4-morpholino-2-(4-nitrophenyl)-5,6-dihydropyrido[3,4-d]pyrimidine-7(8H)-carbothioamide (mn): To a solution of 4-(2-(4-nitrophenyl)-5,6,7,8-tetrahydropyrido[3,4-d]pyrimidin-4-yl)morpholine (lr) (486 mg, 1.4 mmol) in DMF (15 mL) was added dropwise a solution of isothiocyanatomethane (208 mg, 2.8 mmol) in DMF (3 mL) at rt. After 3.5 hrs, LCMS showed reaction proceeded slowly. Additional isothiocyanatomethane (104 mg) was added. It was stirred at rt for 48 hrs. It was diluted with H2O. The solid was filtered off, washed with H2O, dried to afford 443 mg (75%) desired compound mn as a light yellow solid. 1H NMR (500 MHz, DMSO) δ 8.58-8.53 (m, 2H), 8.38-8.33 (m, 2H), 7.93 (d, J=4.2, 1H), 4.91 (s, 2H), 4.04 (t, J=5.1, 2H), 3.77-3.72 (m, 4H), 3.59-3.54 (m, 4H), 2.96 (d, J=4.1, 3H), 2.76 (t, J=5.1, 2H). LC-MS: m/z=+415 (M+H)+.
