A general and efficient iron-catalyzed benzylation of 1,3-dicarbonyl compounds

Various CH-acidic 1,3-dicarbonyl compounds and methyl 3-acetamidobut-2-enoate react with benzylic alcohols to give the corresponding 2-benzylated products in good to excellent yield. Typically, reactions proceed under mild conditions (50-80 degrees C; air) in the presence of catalytic amounts of inexpensive iron chloride hexahydrate. The benzylation of 4-hydroxycoumarin gives the pharmaceutically interesting 4-hydroxy-3-(1-phenyl ethyl)-2H-chromen-2-ones. As an example the anticoagulant Phenprocoumon is prepared in one step from commercially available substrates in 94% yield.