[(S)-1-(3-Bromo-imidazo[1,2-b]pyridazin-6-yl)-pyrrolidin-3-yl]-methyl-amine (951 mg, 3.2 mmol) was taken up in DCM, and ethyl chloroformate (459 uL, 4.8 mmol) and triethylamine (895 uL, 6.4 mmol) were added. The reaction was stirred at room temperature under nitrogen for 1 hour. The reaction mixture was then washed with water then 1N HCl. The DCM layer was dried over magnesium sulfate, filtered and reduced in vacuo to give crude product (1.1 g) that was used as is in part C. LRMS (ESI) m/z 382/384 [(M+H)]+, calc'd for C15H20BrN5O2: 382.26.
