General procedure for the synthesis of 2-amino-4-chlorobenzaldehyde from (2-amino-4-chlorophenyl)methanol: In a 2L three-necked round-bottomed flask, (2-amino-4-chlorophenyl)methanol (32 g, 203.82 mmol) was dissolved in dichloromethane (765 mL), and manganese dioxide (150 g, 1.724 mol) was slowly added under stirring. The reaction mixture was stirred continuously for 40 hours at room temperature and under argon protection. Upon completion of the reaction, the reaction mixture was filtered through a diatomaceous earth pad and the solid residue was washed well with dichloromethane (1000 mL). The filtrates were combined and concentrated under reduced pressure to give 2-amino-4-chlorobenzaldehyde as an orange solid. Yield: 24 g (76.2% yield).
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