Aerobic oxidations catalyzed by colloidal nanogold

Area of Science:

• * Nanochemistry
• * Catalysis
• * Organic Synthesis

Background:

• * Colloidal nanogold (gold nanoclusters in liquid media) are increasingly utilized as quasi-homogeneous catalysts.
• * These catalysts are effective in various aerobic oxidation reactions.
• * Poly(N-vinyl-2-pyrrolidone) (PVP) is a common stabilizing agent for gold nanoclusters.

Purpose of the Study:

• * To review recent advancements in aerobic oxidation reactions catalyzed by gold nanoclusters.
• * To present comprehensive studies on gold clusters (<2 nm) stabilized by PVP.
• * To elucidate the mechanistic roles of generated species in catalytic reactions.

Main Methods:

• * Review of recent literature on gold nanocluster catalysis.
• * Detailed investigation of gold clusters (<2 nm) stabilized by PVP.
• * Mechanistic studies involving electron transfer, superoxide/peroxide species, and Lewis acidity.

Main Results:

• * Demonstrated efficacy of PVP-stabilized gold nanoclusters in alcohol oxidation, α-hydroxylation of benzylic ketones, and organoboronate homocoupling.
• * Showcased utility in formal Lewis acid-catalyzed reactions, including intramolecular hydroalkoxylation and hydroamination of nonactivated alkenes.
• * Mechanistic insights revealed partial electron transfer from gold clusters to O(2), generating catalytically active superoxide/peroxide-like species and Lewis acidic centers.

Conclusions:

• * PVP-stabilized gold nanoclusters are versatile quasi-homogeneous catalysts for diverse organic transformations.
• * The catalytic activity is attributed to the generation of reactive oxygen species and Lewis acidic sites.
• * This work highlights the significant potential of nanogold catalysis in synthetic chemistry.