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Helvetica Chimica Acta Vol. 86 (2003)
8. 4-Bromo-5-chloro-2-nitroaniline (Scheme 2). Preparation of this compound has been reported previously
in unstated yield by hydrolysis of 4-bromo-5-chloro-2-nitroacetanilide with some conc. HCl in boiling EtOH
[19]. A soln. of 4-bromo-5-chloro-2-nitroacetanilide (100 mg, 0.341 mmol) in H2O (10 ml) and conc. H2SO4
(1.5 ml) was refluxed for 2.5 h, at which time TLC (silica gel; CH2Cl2) indicated that no starting material was
present. The soln. was cooled, made alkaline to litmus with KOH pellets, and extracted with CH2Cl2. The extract
was dried (MgSO4) and evaporated in a rotating evaporator to leave a dark yellow solid (80 mg, 0.318 mmol;
93%). M.p. 205 2068 ([19]: yellow, m.p. 202 2038). 1H-NMR (CDCl3): 8.38 (s, 1 H); 6.98 (s, 1 H); 6.08 (s, 2 H).
9. 5-Bromo-6-chlorobenzofurazan 1-Oxide (BrClBF; Scheme 2). Aq. 5% NaOCl was added dropwise to a
red soln. of 4-bromo-5-chloro-2-nitroaniline (200 mg, 0.795 mmol) in ethanolic KOH (60 ml), and a yellow
precipitate started to form, but addition was continued until precipitation stopped, and the solution turned
yellow. The mixture was extracted with CH2Cl2 (3 Â 100 ml), and the extracts were dried (MgSO4), filtered, and
evaporated in a rotating evaporator to leave a residue (180 mg) shown by TLC to contain a little starting
material. Chromatography (silica gel; hexanes/CH2Cl2 2:1) gave a better, but still slightly impure sample
(160 mg). Crystallization from EtOH gave a yellow solid (100 mg, 0.401 mmol; 50%) . M.p. 125 1268. 1H-NMR
(CDCl3): 7.91 (s, 1 H); 7.68 (s, 1 H).
We thank Prof. Frank B. Mallory for the sample of Br2BF. We thank the Wayland E. Noland Research
Fellowship Fund of the University of Minnesota Foundation for research support to M. J. P.
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Received January27, 2003