TY - JOUR
T1 - Conformational Study of (R)-(−)-2,2,2-Trifluoro-1-(9-anthryl)ethanol (Pirkle’s Alcohol) by Dynamic NMR
AU - Jaime, Carlos
AU - Virgili, Albert
AU - Claramunt, Rosa Maria
AU - López, Concepción
AU - Elguero, José
PY - 1991/11/1
Y1 - 1991/11/1
N2 - Observation of anisochronous 1H and 13C NMR signals in (R)-(−)-2,2,2-trifluoro-1-(9-anthryl)ethanol at low temperature indicates that restricted rotation around the C(sp2)–C(sp3) bond occurs. From the coalescence temperature data and the corresponding chemical shift difference, the free energy of activation for rotation was evaluated to be 14.5 kcal mol−1 at 320 K in deuteriochloroform. These results, together with MM2 calculations, indicate that the ground-state conformation is that in which the trifluoromethyl group is almost orthogonal to the anthracene ring. The transition state will correspond then to the conformation in which the CF3 group eclipses the aromatic nucleus. Complete and 13C NMR assignments of the system at the frozen ground state (340 K) were made by homo- and heteronuclear COSY experiments and NOE difference spectroscopy. © 1991, American Chemical Society. All rights reserved.
AB - Observation of anisochronous 1H and 13C NMR signals in (R)-(−)-2,2,2-trifluoro-1-(9-anthryl)ethanol at low temperature indicates that restricted rotation around the C(sp2)–C(sp3) bond occurs. From the coalescence temperature data and the corresponding chemical shift difference, the free energy of activation for rotation was evaluated to be 14.5 kcal mol−1 at 320 K in deuteriochloroform. These results, together with MM2 calculations, indicate that the ground-state conformation is that in which the trifluoromethyl group is almost orthogonal to the anthracene ring. The transition state will correspond then to the conformation in which the CF3 group eclipses the aromatic nucleus. Complete and 13C NMR assignments of the system at the frozen ground state (340 K) were made by homo- and heteronuclear COSY experiments and NOE difference spectroscopy. © 1991, American Chemical Society. All rights reserved.
U2 - 10.1021/jo00023a014
DO - 10.1021/jo00023a014
M3 - Article
VL - 56
SP - 6521
EP - 6523
IS - 23
ER -