General procedure for the synthesis of 3-formyl-4-hydroxybenzonitrile from 5-cyano-2-methoxybenzaldehyde:
B. Synthesis of 2-hydroxy-5-cyano benzaldehyde
31.08 g of 5-cyano-2-methoxybenzaldehyde obtained in the previous step and 24.52 g of lithium chloride were added to 500 mL of N,N-dimethylformamide. The reaction mixture was heated to reflux for 2 h. The solvent was subsequently removed by rotary evaporator. The residue was dissolved in aqueous acidic potassium sulfate solution and extracted with ethyl acetate. The organic phase was washed sequentially with water and saturated sodium chloride solution. After the above treatment, 24.5 g of the target product 2-hydroxy-5-cyanobenzaldehyde was obtained in 86% yield.
