To a rapidly stirred, 0° C., N2 blanketed, suspension of 3-bromo-6-piperazin-1-yl-imidazo[1,2-b]pyridazine dihydrochloride (934.9 mg, 2.6 mmol) and Hunig's base [7087-68-5] (1.8 mL, 10.6 mmol) in dichloromethane (26 mL) was added 2-isocyanato-2-methylpropane [1609-86-5] (340 μL, 2.9 mmol). The suspension was permitted to stir and warm to ambient temperature over 17 h and was then partitioned between brine and ethyl acetate. The organic phase was reduced in volume to precipitate product as 442.1 mg of yellow solid. A 129.3 mg aliquot was purified by preparative RP-HPLC to yield 61.8 mg of 4-(3-bromoimidazo[1,2-b]pyridazin-6-yl)-N-(tert-butyl)piperazine-1-carboxamide as a white powder, mp. 199-200° C. 1H NMR (400 MHz, DMSO-d6) δ ppm 1.28 (s, 8H) 2.51 (s, 1H) 3.30 (s, 1H) 3.39-3.46 (m, 4H) 3.48-3.54 (m, 4H) 7.26 (d, J=10.11 Hz, 1H) 7.61 (s, 1H) 7.88 (d, J=10.11 Hz, 1H). 13C NMR (100 MHz, DMSO-d6) δ ppm 29.15, 43.05, 45.27, 49.94, 99.27, 110.77, 126.00, 131.50, 136.54, 155.16, 156.93. LRMS (ESI) m/z 381.1/383.1 [(M+H)]+, calc'd for C15H21BrN6O: 381.28.
