C-3 alkylation of oxindole with alcohols by Pt/CeO2 catalyst in additive-free conditions

Abstract

In a series of transition metal-loaded CeO₂ catalysts and Pt-loaded catalysts on various supports, Pt-loaded CeO₂ shows the highest activity for the selective C-3 alkylation of oxindole with octanol. The catalyst is effective for alkylation of oxindole and N-substituted oxindole with a series of substituted benzyl, linear, hetero-aryl alcohols under additive-free conditions and is recyclable. Our results demonstrate the first additive-free catalytic system for this reaction. Mechanistic studies show that this system is driven by the borrowing-hydrogen pathway. Structure–activity relationship studies show that co-presence of surface Pt⁰ species on Pt metal clusters and basic support is indispensable for this catalytic system.