Selective one pot multicomponent green synthesis of 3‐[(aryl)(arylthio)methyl]‐1H‐indole derivatives utilizing enhanced Lewis acidic sites of Surfactant‐assisted ZnO catalyst

Abstract

Five different ZnO nanocrystallites (ZnO‐1 to ZnO‐5) were successfully synthesized by a surfactant‐assisted hydrothermal technique using various surfactants. All the ZnO nanocrystallites are thoroughly characterized by XRD, IR, UV‐DRS spectroscopy and FESEM‐EDS analysis. Among the synthesized ZnO nanocrystallites, the CTAB‐assisted synthesized ZnO‐4 exhibited a fine disc‐like morphology with a minimum crystallite size (23 nm). Subsequent to reaction optimization studies, the ZnO‐4 is utilized as an efficient catalyst for one pot‐three component green synthesis of 3‐[(aryl)(arylthio)methyl]‐1H‐indoles (4a–4p) via. condensation of a variety of indoles, aromatic aldehydes and aromatic thiols at room temperature in water. The single‐crystal X‐ray structure of 3‐[(phenyl)(phenylthio)methyl]‐1H‐indole (4a) is also been reported (CCDC 2170437). The Lewis acidic property of the catalyst‐supported probable mechanism is well proposed subsequent to pyridine‐IR studies of the ZnO catalysts. Indeed, CTAB‐assisted synthesized ZnO‐4 was found to be most effective and selective Lewis acid catalyst for the synthesis of a variety of 3‐[(aryl)(arylthio)methyl]‐1H‐indole derivatives in water at ambient temperature with merits like higher yields, lower reaction time, catalyst recovery and reuse.