Synthesis of 4,5-difluoroimidazole

Abstract 5-Fluoroimidazole-4-carboxylic acid ethyl ester was converted to the corresponding hydrazide. Oxidation of the hydrazide to the carbonyl azide and Curtius rearrangement in t -butyl alcohol produced 4- t -butyloxycarbonylamino-5-fluoroimidazole. Dissolution of the t -butyl carbamate in 50% HBF 4 , in situ diazotation of the resulting amine, and irradiation produced the target compound.