title: The preferred conformation of erythro- and threo-1,2-difluorocyclododecanes.
abstract: Cyclododecane adopts a square-like structure with corner and edge CH(2) groups. In this study erythro- and threo-1,2-difluorocyclododecanes were prepared to explore whether the two vicinal C-F bonds, with different relative configurations, preferably locate at corner/edge or edge/edge locations. Conformational analysis comparing the diastereoisomers was explored by using a combination of (19)F{(1)H} NMR spectroscopy, computational studies and, in the case of the threo isomer, X-ray structural analysis. In the lowest energy conformers for both diastereoisomers the vicinal C-F bonds are located corner/edge, rather than edge/edge. These structures avoid placing a C-F bond endo into the ring, and appear to benefit from C-CHF-C angle widening, which relaxes 1,4-H,H transannular interactions.
authors.affiliation: EastChem School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Peer
authors.initials: P
authors.lastname: Kirsch
authors.forename: Tomas
authors.initials: T
authors.lastname: Lebl
authors.forename: Alexandra M Z
authors.initials: AM
authors.lastname: Slawin
authors.forename: David
authors.initials: D
authors.lastname: O'Hagan