Reduction of Aromatic Dimethyl Ene-Dicarboxylates to Dimethyl Succinates with Titanium Ylides

Background: Generally, it was assumed that Tebbe- and Takai-reagents are useful for methenylation reactions. Objective: Applying these reagents to aromatic ene dicarboxylates, unexpectedly the reduction of double bonds was achieved. There is, however, a different behaviour of both reagents. Takai-reagent yields reduction while Tebbe-reagent prefers isomerisation. Methods: A selective and unique method has been shown to reduce a double bond of ene-dicarboxylates while both carboxylic groups are not affected at all. In addition, this method is easy and very cheap using Takai-reagent. Results: If isomerisation is to be carried out, without any reduction of a double bond, Tebbe-reagent can be applied. To our knowledge, such reactions have not been published yet. Conclusion: We have shown a selective methodology to reduce aromatic ene-dicarboxylates with titanium ylides.