Abstract

MORALES-RIOS, Martha S.; SANTOS-SANCHEZ, Norma F.  and  JOSEPH-NATHAN, Pedro. Hindered Rotation in N-Carbomethoxylated Indole Derivatives. Rev. Soc. Quím. Méx [online]. 2001, vol.45, n.4, pp.172-176. ISSN 0583-7693.

N-Carbomethoxyindole derivatives display 1H NMR dynamic processes arising from the hindered rotation about the N-C carbamate bond. Theoretical modeling by Molecular Mechanics predicts two conformational minima A and B, owing to the E and Z isomers of the carbamate group. Conformer A, with the carbonyl carbamate group oriented towards the benzene ring is, in most cases, more stable than the B conformer. A hydrogen bond provides an explanation for the preference of the B conformer in 2. The energy profiles reveal that, between the molecules investigated, compound 3 has the lowest barrier to rotation for the interconversion of the A and B conformers. The relative energies of 3 favored the A conformer in large proportion (97:3). These results are consistent with the observed sharp signals in the ¹H NMR spectrum of 3, while compounds 2, 6 and 7 show some significantly broadened signals in their ¹H and ¹³C NMR spectra.

Keywords : N-carbomethoxyindoles; hindered rotation; dynamic processes; NMR.

        · abstract in Spanish     · text in English     · English ( pdf )