Exploiting 1,2,3-Triazolium Ionic Liquids for Synthesis of Tryptanthrin and Chemoselective Extraction of Copper(II) Ions and Histidine-Containing Peptides

Based on a common structural core of 4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyridine, a number of bicyclic triazolium ionic liquids 1–3 were designed and successfully prepared. In our hands, this optimized synthesis of ionic liquids 1 and 2 requires no chromatographic separation. Also in this work, ionic liquids 1, 2 were shown to be efficient ionic solvents for fast synthesis of tryptanthrin natural product. Furthermore, a new affinity ionic liquid 3 was tailor-synthesized and displayed its effectiveness in chemoselective extraction of both Cu(II) ions and, for the first time, histidine-containing peptides.