Understanding the Chemoselectivity in Palladium-Catalyzed Three-Component Reaction of -Bromobenzaldehyde, -Tosylhydrazone, and Methanol.

To understand the ligand-controlled palladium-catalyzed coupling of -bromobenzaldehyde, -tosylhydrazone, and methanol to give methyl 2-benzylbenzoic ester or methyl ether, we herein investigated the mechanisms which account for how C-C and C-O bonds are formed and why bidentate dppf/dppb ligands afford ester, whereas P(-tolyl) ligand gives ether. The ester chemoselectivity of the bidentate ligands is attributed to the strong electron-donating effect that disfavors the C,Br-reductive elimination of the coupling intermediate of -bromobenzaldehyde and -tosylhydrazone.