Synthesis and 1-oxide/3-oxide interconversion of 4-substituted benzodifuroxans: a thorough NMR and theoretical study of the structure of 4-fluoro- and 4-chloro-benzodifuroxan

The synthesis of the new 4-fluorobenzodifuroxan has been performed in one step from 2,4,6-trifluoro-1,3-dinitrobenzene implying a safe synthesis. Importantly, due to the 1-oxide/3-oxide interconversion, NMR spectra have shown that this compound exists as a mixture of four tautomers. The presence of the fluorine atom allows the determination of the 1H and 13C NMR parameters of the two main isomers. Interestingly, 4-fluorobenzodifuroxan has been partially and totally deoxygenated upon heating with one and two equivalents of triethylphosphite, respectively. Benzodifurazan analog has been obtained in moderate yield and reacts readily with ammonia leading for the first time to 4-aminobenzodifurazan. [Display omitted]