Regenerable N-alkylamide hydroperoxide for catalytic substrate oxidation

Abstract

The use of N-methylpyrrolidinone in a catalytic cycle employing O₂ and H₂ in the presence of transition metal catalysts provides a regenerative hydroperoxide system. When treated with O₂ at 75 °C, N-methylpyrrolidinone is converted into the corresponding hydroperoxide, 5-hydroperoxy-1-methylpyrrolidin-2-one. This stable hydroperoxide undergoes reactions similar to those of tert-butyl hydroperoxide, yielding N-methylsuccinimide as the product. By using either heterogeneous or homogeneous catalysts, N-methylsuccinimide can be reduced with H₂ under mild conditions to the hydroperoxide precursor, N-methylpyrrolidinone. The steps in the conversion of the hydroperoxide into N-methylsuccinimide were elucidated by study of the oxidation of PPh₃ to OPPh₃. Oxygenatom transfer from the hydroperoxide to the phosphine produces the amido alcohol intermediate, 5-hydroxy-1-methylpyrrolidin-2-one. In the presence of O₂, the amido alcohol intermediate undergoes rapid oxidation to N-methylsuccinimide.