[Cl:1][C:2]1[N:3]=[N:4][C:5]([Cl:8])=[CH:6][CH:7]=1.OS(O)(=O)=O.[CH:14]1(C(O)=O)[CH2:17][CH2:16][CH2:15]1>O>[Cl:1][C:2]1[N:3]=[N:4][C:5]([Cl:8])=[CH:6][C:7]=1[CH:14]1[CH2:17][CH2:16][CH2:15]13,6-Dichloropyridazine (10 g) was suspended in water (200 ml), H2SO4 (19.7 g) and cyclobutane carboxylic acid (32.7 g) were added and the reaction degassed under N2 at 70° C. Silver nitrate (2.28 g) was added followed by dropwise addition of ammonium persulfate (45.9 g) in water (120 ml). After an additional 1 hour heating at 70° C., the reaction was poured onto ice, basified to pH 8-9 with aqueous ammonium hydroxide and extracted into ethyl acetate (3×500 ml), dried (MgSO4) and evaporated to dryness. Purified with hexane-ethyl acetate mixtures to obtain pure product (13.4 g). 1H NMR (360 MHz , CDCl3) δ 1.57 (2H, m), 1.82 (4H, m), 2.20 (1H, m), 3.30 (1H, m), 7.38 (1H, s); MS (ES+) m/e 217 [MH]+.
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