Catalytic cross-coupling reaction of esters with organoboron compounds and decarbonylative reduction of esters with HCOONH₄: A new route to acyl transition metal complexes through the cleavage of acyl-oxygen bonds in esters

The Ru₃(CO)₁₂-catalyed cross-coupling reaction of esters with organoboron compounds leading to ketones is described. A wide variety of functional groups can be tolerated under the reaction conditions. Aromatic boronates function as a coupling partner to give aryl ketones. Acyl-alkyl coupling to dialkyl ketones is also achieved by the use of 9-alkyl-9-BBN in place of boronates. The Ru₃(CO)₁₂- catalyzed decarbonylative reduction of esters with ammonium formate (HCOONH ₄) leading to hydrocarbons is also described. No expected aldehydes are produced, and controlled experiments indicate that aldehydes are not intermediate for the transformation. A hydrosilane can also be used as a reducing reagent in place of HCOONH₄. A wide variety of functional groups are compatible for both reactions. The key step for both catalytic reactions is the directing group-promoted cleavage of an acyl carbon-oxygen bond in esters, leading to the generation of acyl transition metal alkoxo complexes.