In a similar manner to Step 2 of Example 16, 3-chloro-4-fluoro-N-(1-methyl-1-phenylethyl)benzamide (3.00 g, 10.3 mmol) was dissolved in THF (120 mL), and the solution was treated with TMEDA (5.00 mL, 32.9 mmol), sec-butyl lithium-hexane solution (1.01 mol/L, 32.6 mL, 32.9 mmol) and DMF (1.80 mL, 22.6 mmol), followed by purification by flash column chromatography (chloroform) and by slurry (chloroform) to obtain 4-chloro-3-hydroxy-5-fluoro-2-(1-methyl-1-phenylethyl)isoindolinone (1.50 g, yield 46%).
