Synthesis of 4,5-difluoroimidazole

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% HBF4, in situ diazotation of the resulting amine, and irradiation produced the target compound.