title: Conformational studies by dynamic NMR. 88.(1) stereomutation processes in the diastereoisomers of a representative amino alcohol and related amide precursors.
abstract: The barriers for three internal motions (i.e., phenyl and tert-butyl rotation as well as N-inversion) have been determined by dynamic NMR spectroscopy in the two diastereoisomeric forms of a typical amino alcohol [dimethylamino-2,4,4-trimethyl-3-phenyl-3-pentanol, Me(2)NCH(2)CHMeC(OH)PhBu(t)]. The two structures were assigned by connection with those of the corresponding amide precursors determined by single-crystal X-ray diffraction. These amides (C=O in place of CH(2)) too were found to undertake internal motions amenable to NMR observation, i.e., phenyl, tert-butyl, and N-CO rotations: the corresponding barriers were also measured. Ab initio computations indicate that H-bonding makes all these molecules adopt six-membered cyclic conformations, a conclusion which agrees well with the X-ray crystal structure determined for the amide precursors.
authors.affiliation: Department of Organic Chemistry A. Mangini, University of Bologna, Viale Risorgimento 4, Bologna 40136, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Bartoli
authors.forename: Stefano
authors.initials: S
authors.lastname: Grilli
authors.forename: Lodovico
authors.initials: L
authors.lastname: Lunazzi
authors.forename: Massimo
authors.initials: M
authors.lastname: Massaccesi
authors.forename: Andrea
authors.initials: A
authors.lastname: Mazzanti
authors.forename: Samuele
authors.initials: S
authors.lastname: Rinaldi