Synthesis
The general procedure for the synthesis of 4-isopropyl-2-nitroaniline from 2,2,2-trifluoro-N-(2-nitro-4-isopropylphenyl)acetamide was as follows: to a stirring solution of 2,2,2-trifluoro-N-(4-isopropyl-2-nitrophenyl)acetamide (2.1 g, 7.6 mmol) in methanol (40 mL) was added sequentially water (20 mL) and potassium carbonate ( 0.5 g, 4 mmol). The reaction mixture was stirred at room temperature for 18 h, followed by partition extraction with ethyl acetate (50 mL) and saturated saline (50 mL). After separation of the organic layer, the aqueous layer was then extracted with ethyl acetate (3 x 25 mL). All organic layers were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (silica gel 230-400 mesh, 150 g, eluting sequentially with 20% and 30% ethyl acetate/hexane solvent mixture) to afford 4-isopropyl-2-nitroaniline 1.18 g (61% yield) as an orange oil. Its NMR hydrogen spectrum (CDCl3) data were as follows: δ 1.23 (6H, d), 2.85 (1H, m), 6.77 (1H, d), 7.28 (1H, dd), 7.96 (1H, d). Mass spectrometry (ESI+) showed the molecular ion peak m/z 181.2 ([M+H]+). The HPLC (Method D) retention time was 3.97 min.
