Example 1 Synthesis of [1H]-isoindolin-1-one-3-carboxylic acid: 10 g (0.0666 mol) of o-carboxybenzaldehyde was dissolved in 100 mL of methanol and cooled to 10°C-15°C. Ammonia was bubbled into this cooled solution for 10 min, followed by stirring for 1 h at room temperature. A solution of 3.26 g (0.0666 mol) of sodium cyanide dissolved in 100 mL of water was slowly added to the stirred reaction mixture over 15 minutes. After addition, stirring was continued for 1 hour at room temperature. Upon completion of the reaction, most of the methanol was removed under vacuum. To the resulting yellow solution 80 mL of 6 N hydrochloric acid was added drop by drop over a period of 10 minutes and a transient precipitate was observed to form and then dissolve. The reaction solution was heated to 100 °C and maintained for 1.5 h, during which a thick yellow precipitate was generated. After the reaction mixture was cooled to room temperature, the yellow solid was collected by filtration and washed sequentially with water and acetone. The crude product was purified by aqueous recrystallization to give 4.14 g of the target compound in 34% yield with a melting point of 205°C. The physical properties of the product were in complete agreement with those reported in the literature (Darapsky et al., J. Prakt. Chem., 146, 307 (1936)).
