Synthesis
General procedure for the synthesis of 4-chloro-2-nitrobenzaldehyde from 4-chloro-2-nitrotoluene: 4-chloro-1-methyl-2-nitrobenzene (8.5 g, 0.05 mol) was dissolved in dimethylformamide (10 mL). N,N-dimethylformamide dimethyl acetal (18 g, 0.15 mol) was then added and mixed with stirring. The reaction mixture was heated to 135 °C and maintained at this temperature for 48 hours. After completion of the reaction, the system was cooled to room temperature. A mixed solution of sodium periodate (32.1 g, 0.15 mol) in water (100 mL) and DMF (50 mL) was slowly added dropwise at a temperature below 20 °C. After the dropwise addition, stirring was continued for 3 h at room temperature to ensure complete reaction. The reaction mixture was filtrated by pumping and the resulting filter cake was washed twice with toluene. The organic phase in the filtrate was separated, washed with water and the solvent was removed by rotary evaporation. The crude product was purified by column chromatography with the eluents in the order of petroleum ether:ethyl acetate=10:1 and petroleum ether:ethyl acetate=5:1 to give 4-chloro-2-nitrobenzaldehyde (5.00 g, 54% yield).
References
[1] Organic and Biomolecular Chemistry, 2018, vol. 16, # 28, p. 5113 - 5118
[2] Journal of Organic Chemistry, 2007, vol. 72, # 26, p. 9857 - 9865
[3] Patent: CN108484497, 2018, A. Location in patent: Paragraph 0045; 0046; 0066; 0067
[4] Patent: DE128727,
[5] Bioorganic and Medicinal Chemistry, 2006, vol. 14, # 7, p. 2462 - 2467
