TY - JOUR
T1 - Determination of rotational barriers of c(sp2)-c(sp3) bonds in 2-arylpiperidines. II.1 1h-dnmr and 13c-dnmr studies of the trans-1,3-dimethyl-2-(3,4,5-trimethoxyphenyl)-4-piperidone
AU - Rubiralta, Mario
AU - Feliz, Miguel
AU - Jaime, Carlos
AU - Giralt, Ernest
PY - 1986/1/1
Y1 - 1986/1/1
N2 - Both 1H-DNMR and 13C-DNMR has been applied to determine the rotational C(sp2)-C(sp3) barrier in hydrochloride of trans-1, 3-dimethyl-2-(3,4,5-trimethoxyphenyl)-4-piperidone (3) synthesized via acid catalyzed cyclization of the precursor iminoketal 4. 2D-NMR experiments allowed the assignment of practically all the 1H- and 13C-NMR signals. Rotational barrier around the C2-Ar bond was shown to be 55.9 KJ/mol-1 at 20 °C by analysis of the variable temperature 1H-NMR spectra and a value of 55.3 KJ mol-1 at 13 °C was found using 13C-NMR. This last procedure was also applied to determine the rotational barrier of 1,3,3-trimethyl-2-(3,4,5-trimethoxyphenyl) -4-piperidone (1) hydrochloride. All the experimental barriers are discussed in terms of the influence of the piperidine ring substituents with the aid of molecular mechanical calculations. © 1986.
AB - Both 1H-DNMR and 13C-DNMR has been applied to determine the rotational C(sp2)-C(sp3) barrier in hydrochloride of trans-1, 3-dimethyl-2-(3,4,5-trimethoxyphenyl)-4-piperidone (3) synthesized via acid catalyzed cyclization of the precursor iminoketal 4. 2D-NMR experiments allowed the assignment of practically all the 1H- and 13C-NMR signals. Rotational barrier around the C2-Ar bond was shown to be 55.9 KJ/mol-1 at 20 °C by analysis of the variable temperature 1H-NMR spectra and a value of 55.3 KJ mol-1 at 13 °C was found using 13C-NMR. This last procedure was also applied to determine the rotational barrier of 1,3,3-trimethyl-2-(3,4,5-trimethoxyphenyl) -4-piperidone (1) hydrochloride. All the experimental barriers are discussed in terms of the influence of the piperidine ring substituents with the aid of molecular mechanical calculations. © 1986.
U2 - 10.1016/S0040-4020(01)87550-5
DO - 10.1016/S0040-4020(01)87550-5
M3 - Article
VL - 42
SP - 3957
EP - 3966
JO - Tetrahedron
JF - Tetrahedron
SN - 0040-4020
IS - 14
ER -