Abstract
Although transition metal phosphides are well studied as electrocatalysts and hydrotreating catalysts, the application of metal phosphides in organic synthesis is rare, and cooperative catalysis between metal phosphides and supports remains unexplored. Herein, we report that a cerium dioxide-supported nickel phosphide nanoalloy (nano-Ni2P/CeO2) efficiently promoted the C-3 alkylation of oxindoles with alcohols without any additives through the borrowing hydrogen methodology. Oxindoles were alkylated with various alcohols to provide the corresponding C-3 alkylated oxindoles in high yields. This is the first catalytic system for the C-3 alkylation of oxindoles with alcohols using a non-precious metal-based heterogeneous catalyst. The catalytic activity of nano-Ni2P/CeO2 was comparable to that reported for precious metal-based catalysts. Moreover, nano-Ni2P/CeO2 was easily recoverable and reusable without any significant loss of activity. Control experiments revealed that the Ni2P nanoalloy and the CeO2 support functioned cooperatively, leading to a high catalytic performance.
Highlights
Transition metal phosphides are well studied as electrocatalysts and hydrotreating catalysts, the application of metal phosphides in organic synthesis is rare, and cooperative catalysis between metal phosphides and supports remains unexplored
The mixture was heated at 120 °C in vacuo, and the temperature was increased to 320 °C under Ar atmosphere
The precipitate was collected by centrifugation and washed with acetone and chloroform to afford the nano-Ni2P
Summary
Transition metal phosphides are well studied as electrocatalysts and hydrotreating catalysts, the application of metal phosphides in organic synthesis is rare, and cooperative catalysis between metal phosphides and supports remains unexplored. Active and reusable non-precious metal-based catalysts for the C-3 alkylation of oxindoles with alcohols remains a great challenge. We report the preparation and application of a cerium dioxide-supported nickel phosphide nanoalloy (nano-Ni2P/CeO2) for the synthesis of C-3 functionalized oxindoles using alcohols through the BH methodology without the need for additives.
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