Acetic Acid → 6-(tert-butyl)phthalazin-1(2H)-one

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In a 250 mL round-bottomed flask, 2,5-di-tert-butyl-3-hydroxyisoindolin-1-one (4.9 g, 18.7 mmol, Eq: 1.00) was combined with acetic acid (60 ml) to give a colorless solution. The reaction was heated to 90° C. Hydrazine monohydrate (1.61 g, 1.57 ml, 20.6 mmol, Eq: 1.1) was added dropwise. The reaction was stirred at 90° C. for 1 h. The reaction mixture was diluted with 24 mL H2O and slowly cooled to 25° C. over 3 h. The reaction mixture was concentrated but not quite to dryness. The reaction mixture was taken up in dichloromethane. The reaction mixture was poured into 75 mL sat NaHCO3 and extracted with dichloromethane (3×50 mL). The organic layers were dried over Na2SO4 and concentrated in vacuo. to give pure product as a white solid, which was purified by flash chromatography (silica gel, 80 g, 1% to 4% MeOH in DCM) to afford the desired product (3.7 g) as a white solid. (M+H)+=203 m/e. 1H NMR (300 MHz, CHLOROFORM-d) δ ppm 0.32 (s, 9 H) 6.58 (d, J=1.89 Hz, 1 H) 6.76 (dd, J=8.31, 1.89 Hz, 1 H) 7.06 (s, 1 H) 7.26 (d, J=8.31 Hz, 1 H) 9.19 (br. s., 1 H).

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