Selective and efficient fluorination of chlorodiazines under solvent-free phase transfer catalysis

3-Chloro-6-phenylpyridazine, 2,3-dichloroquinoxaline and 1,4-dichlorophthalazine were reacted with KF under solvent-free conditions in the presence of a phase transfer agent, with or without microwave irradiation. The chlorine–fluorine exchanges were obtained with enhanced yields and selectivities when compared with previous methods.