Rhenium-Catalyzed Reduction of Carboxylic Acids with Hydrosilanes

Re₂(CO)₁₀ efficiently catalyzes the direct reduction of various carboxylic acids under mild conditions (rt, irradiation 350 or 395 nm). While aliphatic carboxylic acids were readily converted to the corresponding disilylacetals with low catalyst loading (0.5 mol %) in the presence of Et₃SiH (2.2 equiv), aromatic analogues required more drastic conditions (Re₂(CO)₁₀ 5 mol %, Ph₂MeSiH 4.0 equiv) to afford the corresponding aldehydes after acid treatment.