The analysis of the proton magnetic resonance spectra of heteroaromatic systems. IV. Benzofuran, indole, and related compounds

Abstract

The proton magnetic resonance spectra of benzofuran, dibenzofuran, indole, 7-azaindole, carbazole, and 4-azacarbazole (α-carboline) have been investigated at 100 Mc/s, and the spectral parameters for these molecules have been obtained. The presence of cross-ring coupling constants involving the NH proton of indole and carbazole is reported.

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

“…The fact that the 1 H NMR spectra of 1–17 were measured in a highly homogenized magnetic field provides the opportunity to accurately determine all chemical shifts and coupling constants, even allowing to know the small values of inter‐ring coupling constants. The pertinent values for indoles 1–4 are given in Table and include refined data for J 1,4 , J 2,6 , and J 3,7 long‐range spin‐spin interactions, while those values for coumarins 5–10 are given in Table and include the refined data for J 3,5 , J 3,7 , J 4,5 , and J 4,8 values. In turn, the chemical shifts and coupling constants for the ring‐A hydrogen atoms and H‐3 of flavones 11–17 are shown in Table , while those corresponding to ring C are found in Table .…”

Photochemical Studies on the Antiinflammatory Drug Diclofenac

“…The photoproducts were isolated by reverse phase preparative column chromatography and identified (i) by their mass spectra, obtained by direct HPLC-MS and confirmed, after methylation, by GC-MS, and (ii) from the 'H-NMR spectra of the purified samples. 'H-NMR spectral assignments of the three photoproducts were confirmed by comparison with the fully assigned 'H-NMR spectrum of carbazole (Black and Heffernan, 1965), which characterized the H4 and Hs signals to be the most deshielded in the carbazole structure. The final assignments were made after selected proton-proton decoupling experiments.…”

Plant Anticancer Agents V: New Bisindole Alkaloids from Tabernaemontana johnstonii Stem Bark

“…In simple indoles, the 4-proton (corresponding to the 11'-proton of tabernamine) absorbs downfield of the 5-, 6-, and 7-protons; for indole itself in acetone, for example, these resonances occur a t b 7.55,7.00,7.08, and 7.40 ppm, respectively (12). In various methyl indoles, the 4-proton absorbs downfield from the remaining protons at about 6 7.4-7.5 (chloroform) or 7.2 (acetone) ppm (13).…”