34036-07-2

75-29-6

348-61-8

68-12-2

34036-07-2

General procedure: a 5L four-necked flask is equipped with a mechanical stirring device and protected by nitrogen gas. Magnesium strips and 400 g of iodine granules were added sequentially in tetrahydrofuran. 41.7g of 2-chloropropane was slowly added at room temperature, and the addition time was controlled within 10 minutes, and then the reaction was warmed up to 40℃. The reaction was cooled to room temperature upon completion. A tetrahydrofuran solution of 3,4-difluorobromobenzene (654 g of 3,4-difluorobromobenzene dissolved in 700 g of tetrahydrofuran) was added dropwise at 0 to 10 °C, with the dropwise addition time controlled within 50 min. After the dropwise addition, the reaction mixture was kept at room temperature. After completion of the reaction it was again cooled to 0-10°C and a tetrahydrofuran solution of N,N-dimethylformamide (DMF) was added dropwise (291.3 g of DMF dissolved in 300 g of tetrahydrofuran) over a period of 40 min, keeping the temperature below 10°C. Subsequently 700 g of water was added dropwise and the pH was adjusted to about 4 with concentrated hydrochloric acid (about 840 g of hydrochloric acid was required). Phase separation was carried out and the aqueous phase was extracted twice with 500 g of toluene to combine the organic layers. The organic layer was sequentially washed once with 500 g of saturated saline and once more with 500 g of water. Finally, the crude product was concentrated under vacuum at 65 °C to no solvent. The crude product was purified by vacuum distillation to obtain 3,4-difluorobenzaldehyde with a purity greater than 99.5% and a yield of 86%.