title: Conformational studies by dynamic NMR. 93.(1) Stereomutation, enantioseparation, and absolute configuration of the atropisomers of diarylbicyclononanes.
abstract: The structure of 9-(4-methoxyphenyl)-9-(3-methylphenyl) bicyclo[3.3.1]nonane (1) has been determined by single-crystal X-ray diffraction, and the rotation barriers about the two aryl-C9 bonds have been measured by variable temperature NMR spectroscopy in solution. In the case of 9-(4-methoxyphenyl)-9-(1-naphthyl)bicyclo[3.3.1]nonane (3), the barrier involving the naphthyl-C9 rotation was found to be so high as to allow the physical separation of the two atropisomers by enantioselective HPLC at ambient temperature: the absolute configuration could be established on the basis of the corresponding CD spectra. It was also observed that the Ar-C9 rotation barriers of monoaryl-substituted nonanes are much lower than those of the corresponding diaryl-substituted nonanes.
authors.affiliation: Department of Chemistry, University of Basilicata, Via N. Sauro 85, 85100 Potenza, Italy. mazzand@ms.fci.unibo.it
authors.forename: Daniele
authors.initials: D
authors.lastname: Casarini
authors.forename: Carlo
authors.initials: C
authors.lastname: Rosini
authors.forename: Stefano
authors.initials: S
authors.lastname: Grilli
authors.forename: Lodovico
authors.initials: L
authors.lastname: Lunazzi
authors.forename: Andrea
authors.initials: A
authors.lastname: Mazzanti