A highly efficient synthesis of oxindoles using a functionalized silica gel as support for indium(III) acetylacetonate catalyst in an aqueous-acetonitrile medium

Aminopropylsilica gel (APSG) was obtained by the modification of silica gel with 3-aminopropyltriethoxy silane. The indium(III) acetylacetonate complex was then subsequently anchored to yield In(acac)(3)-bonded silica gel (In(acac)(3)-APSG). The structure was investigated and confirmed by surface area (BET), elemental and thermogravimetric analyses, FT-IR. C-13-CPMAS spectral studies and inductively coupled plasma mass spectrometry technique (ICP-MS). The new In(acac)(3)-APSG material was tested in the synthesis of oxindoles derivatives that were synthesized via the electrophilic substitution reaction of indoles with various isatins in water. The catalyst is highly stable and recyclable for several times. The work-up procedure is very simple and oxindoles were obtained in high yields. (C) 2010 Elsevier B.V. All rights reserved.