Nickel-Catalyzed Decarbonylation of Aromatic Aldehydes.

We report here the first systematic study of nickel-catalyzed decarbonylation of aromatic aldehydes under relatively mild conditions. Aldehydes with electron donating groups at para and ortho positions are generally successful with our method. For aldehydes with electron-withdrawing groups, significantly higher yields were achieved for ortho-substituted substrates than para ones, probably due to the effects of steric hindrance or electron donors at the ortho position to suppress the Tishchenko reaction, an undesirable side reaction toward homocoupled esters.