Supported dual‐acidic 1,3‐disulfoimidazolium chlorozincate@HZSM‐5 as a promising heterogeneous catalyst for synthesis of indole derivatives

Abstract

HZSM‐5‐supported Brönsted and Lewis acidic ionic solid 1,3‐disulfoimidazolium chlorozincate materials ([dsim]2[ZnCl4]@HZSM‐5) were synthesized with various ratios (3, 6, 9, 17 and 50% w/w). The heterogeneous materials were characterized via a variety of spectroscopic techniques. Dual acidity of these materials was determined using specified techniques. These acidic solids were examined as stable heterogeneous catalysts for the Fischer indole reaction of equimolar amounts of phenylhydrazine hydrochloride and various aliphatic or aromatic ketones at 80–90°C in neat condition to produce substituted indole derivatives. The efficient 17% ionic salt‐loaded HZSM‐5 composite was easily reused for ten consecutive cycles with a slight loss of its activity. The recycled catalyst was further analysed using powder X‐ray diffraction and inductively coupled plasma optical emission spectrometric techniques.

Study of the catalytic activity of methylene-bridged dicationic –SO3H-functionalized imidazolium phosphomolybdate hybrids for the one-pot sequential synthesis of 3-substituted indoles

“…The connecting alkyl spacer groups between the imidazole rings as well as the methyl groups at the 2 position of the imidazole showed C-H rocking (1350-1392 cm À1 ) along with C-H bending (1450-1470 cm À1 ) bands in the respective IR spectra of the IL-POMs. 66 The peaks observed within the 3300-3500 cm À1 range were assigned to stretching vibrational frequencies of -OH of sulfonic acid groups as well as hydrogen bonded -OH of bound water molecules in the rigid framework of the phosphomolybdate anion. A strong peak was observed at 3458 cm À1 in [DILPOM]-3, which indicated a high extent of hydrogen bond interactions.…”

Synthetic Protocols for Aromatic Nitration: A Review

“…Phosphotungstic acid and Phosphomolybdic acid used as Hybrid polyoxometalates. Regioselectivity, the alternative reagent of H 2 SO 4 and recyclable catalyst are notable advantages of this method [62] …”