Process development and research on the synthesis of p-fluoronitrobenzene by halogen exchange fluorination

Abstract P-fluoronitrobenzene (p-FNB) belongs to the aromatic fluorine containing intermediate, which is the main raw material for the production of biology, medicine, pesticides, and dyes.Over the years, the synthesis methods and technological development of p-fluoronitrobenzene have garnered widespread attention from the industrial and academic sectors, thanks to its high biological activity, low toxicity, outstanding performance, high added value, and low energy consumption. In this study, the halogen exchange fluorination method was employed to synthesize p-fluoronitrobenzene using p-chloronitrobenzene as the starting material. Through the action of phase transfer catalyst, the effects of process parameters such as reaction temperature, reaction time, type and amount of fluorinating agent, type and amount of catalyst, and solvent type were investigated and optimized. The main factors influencing the conversion rate of p-chloronitrobenzene and the yield of p-fluoronitrobenzene product were examined.Experimental results show that using highly active potassium fluoride as the fluorinating agent, with an equivalent ratio of 1.75 to p-chloronitrobenzene, and using tetramethylammonium chloride as the phase transfer catalyst, with a dosage of 4.5% relative to p-chloronitrobenzene, and using DMF as the solvent, the conversion rate and yield of the fluorination reaction can reach 97.86% and 91.58%, respectively, after a 15-hour reaction at 150°C. Under these process conditions, the fluorination reaction exhibits excellent performance and shows good reproducibility in scale-up experiments.