Cl[C:2]1[C:3](=[O:15])[NH:4][N:5]=[CH:6][C:7]=1[O:8][CH2:9][CH:10]1[CH2:14][CH2:13][CH2:12][CH2:11]1.[OH-].[Na+].[H][H]>[Pd].O>[CH:10]1([CH2:9][O:8][C:7]2[CH:6]=[N:5][NH:4][C:3](=[O:15])[CH:2]=2)[CH2:11][CH2:12][CH2:13][CH2:14]1
A pressure vial containing a mixture of 4-chloro-5-cyclopentylmethoxy-2H-pyridazin-3-one (Intermediate 60, 0.75 g, 3.27 mmol), water (12 mL), and a 2N aqueous sodium hydroxide solution (2.1 mL) was treated with 10% palladium on carbon (75.1 mg, 10% weight of 4-chloro-5-cyclopentylmethoxy-2H-pyridazin-3-one). The reaction was then pressurized with hydrogen (40 psi), where it shook overnight. The resulting reaction mixture was removed from the hydrogenator and then warmed with a heat gun and quickly filtered through filter paper. The filter cake was rinsed with warm water and methylene chloride. The filtrate was filtered through filter paper to remove some residual catalyst and washed with methylene chloride. The filtrate was concentrated in vacuo to remove organics. Upon concentrating the aqueous layer was acidified with a 1N aqueous hydrochloric acid solution. The resulting precipitate was collected by filtration, rinsed with water and then dried in vacuo to afford 5-cyclopentylmethoxy-2H-pyridazin-3-one (499.6 mg, 78%) as an off-white solid; ES+-HRMS m/e calcd for C10H14N2O2 [M+H+] 195.1128, found 195.1128. 1H NMR (400 MHz, DMSO-d6) δ ppm 1.23-1.38 (m, 2H), 1.46-1.67 (m, 4H), 1.68-1.82 (m, 2H), 2.23-2.34 (m, 1H), 3.87 (d, J=7.0 Hz, 2H), 6.17 (s, 1H), 7.65 (d, J=2.6 Hz, 1H), 12.61 (br s, 1H).
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