Diastereoface-discriminative metal coordination in asymmetric synthesis: D-pantolactone as practical chiral auxiliary for Lewis acid catalyzed Diels-Alder reactions
TiCl4-catalyzed Diels-Alder additions of the acrylate of commercial D-pantolactone to cyclopentadiene, isoprene and butadiene proceed with very high diastereofacial selectivity. Practical and mechanistic aspects of these reactions are discussed.