Coupling of a C2-chiral ferrocene with phenylalkynyl groups: novel ferrocenophanes carrying multiple chiral ferrocenyl units.

Upon treatment with CuCl/TMEDA (1:1) at a high [CuCl]/[1] ratio, enantiopure C(2)-chiral tetrasubstituted ferrocene 1 carrying phenylalkynyl groups is transformed into a novel family of chiral ferrocenophanes 2 and 3 with their ferrocenyl joints connected by a pi-conjugated rigid bridge. Compound 3, which is reminiscent of the Escher's endless staircase, is a single conformer with a one-handed helical chirality.