title: Conformational studies by dynamic NMR. 86. Structure, stereodynamics, and cryogenic enantioseparation of the stereolabile isomers of o-dinaphthylphenyl derivatives.
abstract: Static and dynamic stereochemistry of the hydrocarbon comprising a phenyl ring bearing two alpha-naphthyl substituents in the ortho positions, i.e., 1,2-di-(4-methyl-naphth-1-yl)-benzene 1, has been studied by a combination of variable temperature NMR, cryogenic HPLC, and MM calculations. Whereas in solution both syn (meso) and anti (chiral) forms were observed and the corresponding interconversion barrier was determined (Delta G(++) = 19.5 kcal mol(-1)), only the diastereoisomer anti was found to be present in the crystalline state (X-ray diffraction). When the molecule is rendered asymmetric by introduction of a nitro group in the phenyl ring as in 1,2-di-(4-methyl-naphth-1-yl)-4-nitrobenzene 2, the chiral syn and anti diastereoisomers are simultaneously present both in solution and in the solid state, albeit in different proportions. Cryogenic chromatography on a HPLC chiral stationary phase at 20 degrees C allowed the stereolabile diastereoisomers and the corresponding enantiomers to be separated.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 31, Genova 16146, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: DellErba
authors.forename: Francesco
authors.initials: F
authors.lastname: Gasparrini
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
authors.forename: Marino
authors.initials: M
authors.lastname: Novi
authors.forename: Marco
authors.initials: M
authors.lastname: Pierini
authors.forename: Cinzia
authors.initials: C
authors.lastname: Tavani
authors.forename: Claudio
authors.initials: C
authors.lastname: Villani