Influence of Lewis Acids on the [4 + 2] Cycloaddition of N,N′-Fumaroylbis[(2R)-bornane-10,2-sultam] to Cyclopentadiene and application to various dienes

Among seventeen different Lewis acids, TiCl₄ was found to be the best catalyst for the 4 + 2] cycloaddition of cyclopentadiene to N,N′-fumaroylbis(2R)-bornane-10,2-sultam] ((?)- 1 ). Independently of the TiCl₄ molar concentration, almost constant and complete (98–89% d.e.) diastereofacial π-selection was achieved in the Diels-Alder addition of (?)- 1 to cyclopentadiene, cyclohexadiene, isoprene, and 2,3-dimethylbuta-1,3-diene.