A MnCl₂-catalyzed synthesis of aldehydes from organohalides by using samarium metal in DMF

A novel coupling reaction between organohalides and N,N-dimethylformamide (DMF) catalyzed by MnCl₂ was investigated in the presence of samarium metal under mild conditions. A variety of aliphatic, aromatic and heterocyclic aldehydes were produced with good yields in one pot. Bromo substrates showed the most efficient reactivity among the organohalides used in the experiments, and 10 mol% MnCl₂ was sufficient to catalyze the reaction. The reaction proceeds smoothly and can be scaled up to the gram level. This is the first combination of samarium and manganese in organic synthesis. Unlike cuprous iodide or silver nitrate, manganese chloride can promote the formation of aliphatic aldehydes. The reaction mechanism is also discussed.