A new silica-supported organocatalyst based on L-proline: An efficient heterogeneous catalyst for one-pot synthesis of spiroindolones in water

• Preparation of a new heterogeneous organocatalyst based on L-proline.
• L-proline moieties covalently connected to the silica using silica-oxiran substrate.
• Introduction of new strategy for synthesis of new materials based on silica.
• Efficient synthesis of spiroindolones under green conditions.

A simple and practical synthetic strategy for the synthesis of a novel silica-supported organocatalyst system based on L-proline (SSLP) has been developed. First, silica was treated with trimethoxy(vinyl)silane to produced a vinyl-silica (VS) substrate. Then, VS was oxidized using H2O2 to generate the silica-oxiran (SO) material. Finally, ring-opening of oxiranes in SO substrate with L-proline was resulted the production of SSLP catalyst. The catalytic performance of SSLP was evaluated in the three-component synthesis of spirooxindole derivatives via the condensation reaction of isatins and dicarbonyl compounds in water. All reactions were completed in short times and all products were obtained in good to excellent yields. Besides, SSLP could be recovered for 8 times without any additional treatments.

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