Stereospecific 5JHortho,OMe couplings in methoxyindoles, methoxycoumarins, and methoxyflavones

Long‐range coupling constants 5JHortho,OMe were measured in series of methoxyindoles, methoxycoumarins, and methoxyflavones by the modified J doubling in the frequency domain method. The COSY and NOESY spectra revealed the coupling of the –OMe group with a specific proton at the ortho position and i...

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Bibliographic Details
Published in:Magnetic resonance in chemistry 2014-09, Vol.52 (9), p.491-499
Main Authors: Alvarez-Cisneros, Celina, Muñoz, Marcelo A., Suárez-Castillo, Oscar R., Pérez-Hernández, Nury, Cerda-García-Rojas, Carlos M., Morales-Ríos, Martha S., Joseph-Nathan, Pedro
Format: Article
Language:English
Subjects:
long-range coupling constants
methoxycoumarins
methoxyflavones
methoxyindoles
PERCH spin-spin simulation
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Summary:Long‐range coupling constants 5JHortho,OMe were measured in series of methoxyindoles, methoxycoumarins, and methoxyflavones by the modified J doubling in the frequency domain method. The COSY and NOESY spectra revealed the coupling of the –OMe group with a specific proton at the ortho position and its preferred conformation. Homonuclear 1H–1H couplings were confirmed by irradiation of the –OMe signal. Density functional theory calculations of 5JHortho,OMe using the modified aug‐cc‐pVTZ basis set evidenced that the Fermi contact term shows good agreement with the experimental J values. Accurate chemical shift and coupling constant values followed after iterative quantum mechanical spectral analysis using the PERCH software. Copyright © 2014 John Wiley & Sons, Ltd. Long‐range coupling constants 5JHortho,OMe were measured in series of methoxyindoles, methoxycoumarins, and methoxyflavones by the modified J doubling in the frequency domain method. The COSY and NOESY spectra revealed the coupling of the –OMe group with a specific proton at the ortho position and its preferred conformation. Homonuclear 1H–1H couplings were confirmed by irradiation of the –OMe signal. Density functional theory calculations of 5JHortho,OMe using the modified aug‐cc‐pVTZ basis set evidenced that the Fermi contact term shows good agreement with the experimental J values. Accurate chemical shift and coupling constant values followed after iterative quantum mechanical spectral analysis using the PERCH software.
ISSN:0749-1581
1097-458X
DOI:10.1002/mrc.4103