To a solution of tert-butyl 2-isopropyl-3-oxopiperazine-1-carboxylate (200 mg, 0.83 mmol) in NMP (3 mL) were added 2-bromo-4-(methylsulfonyl)aniline (207 mg, 0.83 mmol), (1R,2S)—N1,N2-dimethylcyclohexane-1,2-diamine (12.0 mg, 0.08 mmol), K3PO4.3H2O (660 mg, 2.48 mmol) and Cul (16 mg, 0.08 mmol). The mixture was stirred at 150° C. for 1 h in a microwave oven. The mixture was diluted with water (10 mL) and extracted with EtOAc (3×10 mL). The combined organic layers were washed with brine (10 mL), dried over anhydrous Na2SO4, filtered, concentrated and purified by preparative TLC with CH2Cl2/MeOH 35/1 to afford tert-butyl 1-isopropyl-7-(methylsulfonyl)-3,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrazine-2(1H)-carboxylate (110 mg, 34% yield) as a white solid. LC-MS m/z 394.1 [M+H]+. 1H NMR (CDCl3 400 MHz): δ 7.94 (s, 1H), 7.83-7.76 (m, 2H), 5.35-5.17 (m, 1H), 4.73-4.42 (m, 1H), 4.22-4.12 (m, 1H), 4.11-3.99 (m, 1H), 3.53-3.37 (m, 1H), 3.03 (s, 3H), 2.38-2.27 (m, 1H), 1.42 (s, 9H), 1.19 (d, J=6.8 Hz, 3H), 0.97 (d, J=6.8 Hz, 3H).
