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 (HCOONH4) 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. Copyright 2004 American Chemical Society