Applying Le Chatelier's Principle for a Highly Efficient Catalytic Transfer Hydrogenation with Ethanol as the Hydrogen Source

While isopropanol or formic acid derivatives are mainly applied as hydrogen sources in catalytic transfer hydrogenation reactions, there are only a few reports on the use of primary alcohols. In the present communication we report that ecologically benign and cheap ethanol can be applied with a ruthenium(II) that is completely stable against moisture and oxygen. Catalytic transfer hydrogenation is an equilibrium reaction. Therefore, a rapid removal of acetic aldehyde being formed as the product of ethanol oxidation is the key for high conversions. The reaction shows a broad substrate scope and allows the hydrogenation of ketones, aldehydes and imines.