MECHANISTIC INSIGHT INTO CATALYTIC AEROBIC CHEMOSELECTIVE α-OXIDATION OF ACYLPYRAZOLES

摘要

Mechanistic studies on catalytic aerobic chemoselective α-oxidation of acylpyrazoles, including control experiments, kinetic isotope effect experiments, and radical clock experiments, are described. The key to promoting the reaction was the in-situ generation of a copper(II) peroxo complex, which serves as a Lewis acid/Br0nsted base cooperative catalyst for efficient enolization. The present catalysis was applicable to late-stage α-oxidation of functionalized acylpyrazoles. A preliminary diastereoselective reaction using readily available chiral acylpyrazoles demonstrated that the present catalysis provided access to optically active α-hydroxy acid derivatives.