Biomimetic catalytic aerobic oxidation of C–sp(3)–H bonds under mild conditions using galactose oxidase model compound Cu(II)L

Developing highly efficient catalytic protocols for C–sp(3)–H bond aerobic oxidation under mild conditions is a long-desired goal of chemists. Inspired by nature, a biomimetic approach for the aerobic oxidation of C–sp(3)–H by galactose oxidase model compound Cu(II)L and NHPI (N-hydroxyphthalimide) was developed. The Cu(II)L–NHPI system exhibited excellent performance in the oxidation of C–sp(3)–H bonds to ketones, especially for light alkanes. The biomimetic catalytic protocol had a broad substrate scope. Mechanistic studies revealed that the Cu(I)-radical intermediate species generated from the intramolecular redox process of Cu(II)LH(2) was critical for O(2) activation. Kinetic experiments showed that the activation of NHPI was the rate-determining step. Furthermore, activation of NHPI in the Cu(II)L–NHPI system was demonstrated by time-resolved EPR results. The persistent PINO (phthalimide-N-oxyl) radical mechanism for the aerobic oxidation of C–sp(3)–H bond was demonstrated.