 The X-ray structure of the catalyst showed a stereodefined environment.In 1993, Wulff and coworkers found a complex derived from diethylaluminium chloride and a “vaulted” biaryl ligand below catalyzed the enantioselective Diels-Alder reaction between cyclopentadiene and methacrolein.The chiral ligand is recovered quantitatively by silica gel chromatography.