FT-IR spectra were registered on a Bruker IFS 55 Equinox FTIR spectrophotometer as KBr discs. 1H-NMR (600 MHz) and 13C-NMR (125 MHz) spectra were obtained at room temperature with Bruker-600 equipment using TMS as internal standard and CDCl3 as solvent. Analytical grade chemicals (Sigma-Aldrich Corporation) were used throughout the project. Deionized water was used for the preparation of all aqueous solutions.
General procedure for the nitration of Eugenol
In general, eugenol (1 mmol) and bismuth nitrate pentahydrate (1 eqv.) were mixed and the mixture was studied under different conditions varying the method, solid support and/or solvent as mentioned in Table 1. A representative experimental procedure (entry 2) is as follows: Eugenol (1 mmol) and silica gel (500 mg) was added to a suspension of bismuth nitrate pentahydrate (1 eqv.) in dry benzene (20 mL). The mixture was refluxed using Dean-Stark water separator for 2 h. The progress of the reaction was monitored by TLC. The reaction mixture was then repeatedly extracted (3 × 10 mL) with dichloromethane, washed with saturated solution of sodium bicarbonate, brine and water successively. The organic layer was dried over anhydrous sodium sulfate and concentrated to afford the crude product which was purified by column chromatography (silica gel, hexane/ethyl acetate).
sticky mass; IR (KBr disc, cm-1): 2369, 1522, 1457, 1243, 1136, 1061, 941, 810 and 712; 1H NMR (CDCl3, 600 MHz) δ: 10.67 (s, 1 H), 7.45 (s, 1 H), 6.84 (s, 1 H), 5.89 (m, 1 H), 5.05 (m, 2 H), 3.83 (s, 3 H), 3.27 (d, 2 H, J = 1.1 Hz). 13C NMR (CDCl3, 125 MHz) δ: 149.86, 144.88, 135.94, 133.64, 132.46, 128.63, 127.43, 125.07, 56.70, 36.74.