Laccase-Catalyzed Aniline Oxidation

Vinyl aniline (30 mg, 0.3 mmol) was dissolved in 1.5 mL of sodium acetate buffer (pH 5, 50 mM) and incubated with T. versicolor laccase (36 U mmol⁻¹_substrate) overnight at 27 °C and 180 rpm in an orbital thermoshaker. After attesting the formation of a more polar UV-visible spot in TLC analysis (petroleum ether–EtOAc = 1:1), an additional aliquot of enzyme was added doubling its concentration and the mixture was left reacting for 6 h. The reaction mixture was then extracted with EtOAc and the combined organic layers were dried over Na₂SO₄ and concentrated in vacuo affording a crude mixture. The more polar spot (compound 3a, R_f = 0.25 in petroleum ether–EtOAc = 7:3) was isolated by means of flash column chromatography on silica gel (petroleum ether–EtOAc = 7:3 → 4:6) and fully characterized (isolated yield = 40%). ¹H-NMR (400 MHz; CDCl₃, r.t.): δ 7.01 (AA’BB’ system, 2H), 6.61 (AA’BB’ system, 2H), 3.42–3.34 (m, 1H), 2.25–2.19 (m, 1H), 2.06–2.02 (m, 2H). ¹³C-NMR (101 MHz; CDCl₃, r.t.): δ 144.3, 135.1, 127.5, 119.5, 115.1, 47.9, 25.9. MS (ESI): calcd for [C₁₆H₁₀N₂]⁺ 239.15428, found 239.15410.