[N:1]1[N:5]2[CH:6]=[N:7][C:8](=[O:10])[CH2:9][C:4]2=[CH:3][CH:2]=1.[I:11]N1C(=O)CCC1=O>CN(C=O)C>[I:11][C:3]1[CH:2]=[N:1][N:5]2[C:4]=1[CH2:9][C:8](=[O:10])[N:7]=[CH:6]2Pyrazolo[1,5-c]pyrimidin-5(4H)-one (1.0 g, 7.4 mM, 1.0 equiv) and N-iodosuccinimide (1.67 g, 7.4 mM, 1.0 equiv) were combined with 20 mL of DMF and warmed slightly. Within minutes a heavy precipitate formed. The reaction mixture was stirred an additional 1 h at ambient temperature then cooled on an icewater bath and filtered. The collected solid was washed with 20 mL of dichloromethane and air dried to give 1.66 g (86%) of 3-iodopyrazolo[1,5-c]pyrimidin-5(4H)-one. LCMS (ESI) m+H=262.2; 1H NMR (400 MHz, DMSO-d6) δ: 12.1 (s, 1H), 8.5 (d, 1H, J=7.6), 7.84 (s, 1H), 6.01 (d, 1H, J=7.1).
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