Introduction of novel brønsted acidic ionic liquids with perchlorate counter-anion for one-pot synthesis of symmetric 3,3′-diaryloxindoles

Abstract

In this work, three novel 1,4-butane sultone-based Bronsted acidic ionic liquids with Perchlorate conter-anion are prepared. These newly introduced ionic liquids were synthesized from a two-steps reaction. The reaction includes ring opening of 1,4-butane sultone using 1,4-dimethylpiperazine or 1,10-phenantroline as nitrogen nucleophile sources to obtain zwitterions and then follow by acidification treatment with perchloric acid to obtain three novel Bronsted acidic ionic liquids. The prepared task specific ionic liquids and their stable intermediates were characterized by FT-IR, 1HNMR, 13C-NMR, UV–Vis, TGA and CHNS analysis techniques. The prepared ionic liquids are fully water soluble and have good thermal stability up to 200 °C or higher. Their catalytic efficiency was checked for the preparation of symmetric 3,3′-diaryloxindoles compounds. It was found that the introduced acidic ionic liquids are completely green, environmental benign, task specific and have high catalytic stability. These novel acidic ionic liquids are simply separable by extraction from organic phase by solving in water up to six consecutive runs and give the target products in short reaction times at high yields.