An Enantiomerically Pure Alleno-Acetylenic Macrocycle: Synthesis and Rationalization of Its Outstanding Chiroptical Response

摘要

Chiral allenes attract increasing interest owing to the development of improved syntheses and their emerging use in pharmaceuticals. While strained small-ring allenes have been investigated in greater detail for their theoretical properties and their limits of stability and isolability, allenic macrocycles, in particular shape-persistent ones, are mostly unknown. The scarcity of allenic macrocycles is rather surprising in view of the opportunities for creating new nonplanar, chiral topologies and for developing new chiral host molecules. The first allenic macrocycle known was a [3_4]cyclophane, reported by Krause and co-workers, in which four p-phenylene moieties are bridged by four 1,3-dimethylallene-1,3-diyl linkers and which was isolated as a mixture of several stereoisomers. Fallis and co-workers reported the preparation of the first optically active alleno-phanes. Despite their elegant methodologies, clear proof oi the enantiomeric purity of the final compounds was nol provided. Furthermore, the absolute configuration of the allene moieties was not unambiguously determined, but only inferred from the reaction mechanism.