<i>Anti</i>-Selective Organocatalytic Michael Addition between Phenylacetaldehyde and Nitrostyrene

Using the reaction between phenylacetaldehyde and nitrostyrene catalyzed by pyrrolidine as a simple model, we have studied the diastereochemical outcome of the organocatalytic Michael reactions between benzylic aldehydes and nitrostyrenes. We found that the <i>anti</i> adduct was obtained in high yield and diastereoselection as was demonstrated by the X-ray structure of the product. <i>In situ</i> NMR studies showed a different reaction pathway when compared to aliphatic aldehydes that yield the <i>syn</i> adduct as major isomer.