Improved Regioselective Di-nitration of Biphenyl over Reusable HBEA-500 Zeolite

Experimental

General Procedure of Nitration. All reactions were carried out in a 50 mL one-necked round bottomed flask equipped with a water condenser and a magnetic stirrer. In a typical experiment, a mixture of zeolite HBEA-500 (0.30 g) which was calcined at 550 °C for 2 h in air prior to use, biphenyl (0.61 g, 4 mmol), nitric acid (95%, 0.35 mL, 8 mmol) was stirred in acetic anhydride (5.0 mL) at −5 °C for 24 h. When the reaction was over, 10 mL of dichloro-methane was added, then the zeolites was removed by filtration and the filtrate was washed with water (3 × 10 mL) and 5% aqueous solution of NaHCO3 (10 mL) and water (3 × 10 mL). The organic phase separated was dried with anhydrous sodium sulfate, and filtrated to give a straw yellow liquid. The isomer distribution and yields of products were estimated from the peak areas based on the internal standard technique using gas chromatography. The straw yellow products with further purification by column chromato-graphy, and were identified by comparison of their analytical data with those of authentic samples.

Catalyst Regeneration. The used zeolite was recovered from the reaction mixture by filtration and washed with dichloromethane. The catalyst was dried at 110 °C for 4 h in the oven and ground into powder, then, calcined at 550 °C for 6 h.

1H-NMR of Nitrated Products: 2-Nitrobiphenyl yellow oil 1H NMR (400 MHz, CDCl3) δ 7.8 (d, 1H), 7.6 (d, 1H), 7.5 (m, 1H), 7.4 (m, 4H), 7.3 (m, 2H).

4-Nitrobiphenyl White Solid: 1H NMR (400 MHz, CDCl3) δ 8.3 (m, 2H), 7.7 (m, 2H), 7.6 (d, 2H), 7.5 (d, 2H), 7.4 (d, 1H).

2,2'-Dinitrobiphenyl Yellow Solid: 1H NMR (400 MHz, CDCl3) δ 8.3 (d, 2H), 7.7 (t, 2H), 7.6 (t, 2H), 7.3 (d, 2H).

2,4'-Dinitrobiphenyl Yellow Solid: 1H NMR (400 MHz, CDCl3) δ 8.2 (d, 2H), 8.0 (d, 1H), 7.7 (t, 1H), 7.6 (t, 1H), 7.5 (d, 2H), 7.4 (d, 1H).

4,4'-Dinitrobiphenyl Yellow Solid: 1H NMR (400 MHz, CDCl3) δ 8.4 (d, 4H), 7.7 (d, 4H).