Complete π-Facial Stereoselectivity in the TiCl4-Mediated [4 + 2] Cycloaddition of Cyclopentadiene to N,N′-fumaroyldi[(2R)-bornane-10,2-sultam]

Under the co-operative influence of two prosthetic groups, and independent of the TiCl₄ concentration, complete and constant diastereofacial π-selection was achieved during the [4 + 2] cycloaddition of cyclopentadiene to N,N′-fumaroyl-di[(2R)-bornane-10,2-sultam] ((?)- 1c ); reactive conformations are discussed.