Palladium on carbon-catalyzed α-alkylation of ketones with alcohols as electrophiles: Scope and mechanism

The alpha-alkylation of ketones with alcohols represents a green strategy for the formation of crucial carbon-carbon bonds since it only produces water as byproduct. In terms of reaction mechanism, the evidence for homogeneous catalysis supports a catalytic hydrogen-borrowing pathway; however, the reaction mechanism has not been investigated for heterogeneous Pd/C catalysts. Here, we report an improved method for alpha-alkylation of ketones with alcohols using commercially available Pd/C, ubiquitous in organic synthesis labs, as catalyst. The reaction conditions are mild compared to state-of-the-art for both homoand heterogeneous catalysts, and the developed conditions produces quantitative yields for most ketones and alcohols. A hot filtration experiment and recycling of the catalyst supports the heterogeneous nature of catalysis. Importantly, the reaction mechanism is studied for the first time by a combination of stoichiometric experiments and kinetic analyses by in-situ IR (React-IR). (C) 2019 Elsevier Inc. All rights reserved.