A study of the advantages of using manganese, an inexpensive
and nontoxic metal, to perform stereoselective β-elimination
reactions and to promote sequential olefination reactions of aldehydes
to obtain α,β-unsaturated esters and amides is
presented. Various elimination reactions, all of them characterized
by occurring with complete stereoselectivity and in high yields,
were performed using active manganese (Mn*) as metalating
agent. This ability of manganese has been applied to develop a novel
and direct synthesis of (E)-α,β-unsaturated
esters or amides and (Z)-α,β-unsaturated α-halo
esters and α-choroamides through a Mn*-mediated sequential
olefination protocol of aldehydes with dichloro esters or amides
and trihalo esters or trichloroamides, respectively.
manganese - elimination reactions - stereoselectivity - α,β-unsaturated esters - α,β-unsaturated
amides - metalation
