title: Interplay between the diamine structure and absolute helicity in Ni-salen metallofoldamers.
abstract: The nature of internal chiral diamines can greatly influence the ratio of helical diastereomers for Ni-salen based metallofoldamers. The diastereomer ratio is small for metallofoldamers derived from (1R, 2R)-cyclohexanediamine, (11R, 12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-diamine, or (1R, 2R)-cyclopentanediamine. By contrast, the foldamer from (1S, 2S)-1,2-diphenylethylenediamine provides a relatively large bias (6 : 1) for the P-helical diastereomer as evidenced by NMR studies, chiroptical data, and X-ray studies. A model is proposed to explain the origin of the helical bias. These findings underscore the need to consider helical diastereomers in models for asymmetric induction in metal-salen catalyzed reactions.
authors.affiliation: Brown Laboratories, Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19803, USA.
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Dong
authors.forename: Shi
authors.initials: S
authors.lastname: Bai
authors.forename: Glenn P A
authors.initials: GP
authors.lastname: Yap
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Fox