Continuous flow reactor for Balz–Schiemann reaction: a new procedure for the preparation of aromatic fluorides

A facile and highly efficient procedure for the preparation of aromatic fluorides by Balz–Schiemann reaction via two continuous flow reactors has been set up. The continuous diazotization reactor was run at about 25 °C with residence times of 10–20 s, and the continuous fluorodediazoniation reactor was performed with a residence time of 1 min in high yields. The reaction times can be greatly reduced by increasing temperature and thereby taking advantage of superior mass and heat transfer of a continuous flow system.