Lewis acid-catalyzed asymmetric cycloaddition reaction of 1-(SR)-p-tolylsulfinyl-3-penten-2-one with cyclopentadiene

The asymmetric cycloaddition reaction between 1-(S-R)-p-tolysulfinyl-3-penten-2-one (1) and cyclopentadiene was performed by the catalysis of Lewis acids 2. The diastereoselectivity dependent on the size of aryl substituent involved in the chiral ligands was discussed. The cycloadduct 3 was achieved in a high yield and a high optical purity. The absolute configuration of the cycloadduct 3 was confirmed.