Oxazolidine Formation, or Loss of Acid, from Attempted Fluorination of Amide Side-Chain in 2-Nitroimidazoles

Reaction of Etanidazole (a 2-nitroimidazole derivative with an amide side-chain containing a hydroxyethyl group) with triflic anhydride gives, depending on conditions, a trifluoromethyl(sulfonyl)oxazolidine via a cyclization reaction, or a fluorine-free formate derivative; reaction with tosyl chloride gives only a chloroethyl derivative. An attempt to replace a Br-atom in a related propyl-containing amide side-chain by a F-atom forms instead a propylene derivative via loss of HBr. The studies stem from interest in use of 2-nitroimidazoles with fluorine-containing amide side-chains as hypoxia markers.