Asymmetric Michael Addition of Cyclohexanone or Cyclopentanone to Chalcones Catalyzed by an L ‐Proline‐Based Organic Phosphane

An organophosphane catalyst derived from L‐proline was shown to be a very effective catalyst for asymmetric Michael addition reactions of various chalcones to cyclic ketones including both cyclohexanone and cyclopentanone. The corresponding adducts could be obtained in high yields (up to 91 %) and with excellent enantioselectivities (up to 99 % ee) and diastereomeric ratios (up to >99:1). A possible catalytic mechanism, based on 31P NMR and ESI‐MS observations, for this organophosphane‐catalyzed Michael addition has been proposed.