Selective fluorination by halogen exchange of chlorodiazines and chloropyridines promoted by the ‘proton sponge’—triethylamine tris(hydrogen fluoride) system
The ‘proton sponge’—triethylamine tris(hydrogen fluoride) mixtures provide a mild and efficient fluorinating reagent to introduce selectively fluorine atoms by halogenexchange into chlorodiazines and chloronitropyridine series.
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. (C) 2004 Elsevier B.V. All rights reserved.