Nitration of Simple Aromatics with NO₂ under Air Atmosphere in the Presence of Novel Brønsted Acidic Ionic Liquids

Abstract

Aromatics nitrate with NO₂/air catalyzed by novel Brønsted acidic ionic liquids (ILs) without any volatile chlorinated organic solvent under mild conditions. The ILs employed were caprolactam based, [Caprolactam]X (X⁻=pTSO⁻, BSO⁻, BF₄ ⁻, NO₃ ⁻), which are of relatively lower cost and lower toxicity than traditional imidazolium‐based ILs. The nitration reactions were carried out at −15 to −0°C first, then at room temperature for a longer time with a little excessive NO₂ (ca. 1.4 eqv.) for moderate yield (for toluene). The IL could be reused four times.

Keywords:

• aromatics
• nitration
• NO₂/air
• novel Brønsted acidic ionic liquids