“…Thus, 1-aminotetrahydroquinolines undergo reaction with suitable ketones in the Fischer indole synthesis, 2 and simple tetrahydroquinolines react with α-halo ketones in the Bischler indole synthesis. 3 An alternative general approach focuses on cyclisation reactions of 1-or 7-substituted indoles to complete the tetrahydroquinoline ring. More generally, Nallylindoles undergo acid-catalysed cyclisation on to C7, 4,5 but similar methodology has also been applied for the cyclisation of 7-allylindoles on to N1.…”
A range of 7,9-dimethoxypyrrolo[3,2.1-ij]quinolines have been prepared by the cyclisation of 7-formyl-1-diethylcarbethoxyindoles. The functionality at C5 has been varied by the conversion of the carbethoxy group into carboxy, azidocarbonyl and isocyanate groups. The hydroboration of a previously reported pyrroloquinolone gave a related 5-hydroxypyrrolo[3,2,1-ij]quinolone, and the hydroxyl group was sequentially converted into tosylate, azido and amino groups.
“…Thus, 1-aminotetrahydroquinolines undergo reaction with suitable ketones in the Fischer indole synthesis, 2 and simple tetrahydroquinolines react with α-halo ketones in the Bischler indole synthesis. 3 An alternative general approach focuses on cyclisation reactions of 1-or 7-substituted indoles to complete the tetrahydroquinoline ring. More generally, Nallylindoles undergo acid-catalysed cyclisation on to C7, 4,5 but similar methodology has also been applied for the cyclisation of 7-allylindoles on to N1.…”
A range of 7,9-dimethoxypyrrolo[3,2.1-ij]quinolines have been prepared by the cyclisation of 7-formyl-1-diethylcarbethoxyindoles. The functionality at C5 has been varied by the conversion of the carbethoxy group into carboxy, azidocarbonyl and isocyanate groups. The hydroboration of a previously reported pyrroloquinolone gave a related 5-hydroxypyrrolo[3,2,1-ij]quinolone, and the hydroxyl group was sequentially converted into tosylate, azido and amino groups.
“…The pyrrolo[3,2,1-ij]quinoline framework can be synthesised by cyclisation of tetrahydroquinoline derivatives to complete the indole ring, 1,2 or by cyclisation of 1-or 7-substituted indoles to complete the tetrahydroquinoline ring. [3][4][5][6][7][8][9][10][11] Our methodology in this work has involved the specific activation at C7, as a consequence of placing the electron-donating methoxy groups at C4 and C6.…”
4,6-Dimethoxy-3-substituted-indole-7-carbaldehydes and 4,6-dimethoxy-3-substituted-indole-2carbaldehydes undergo reaction with dimethyl acetylenedicarboxylate and triphenylphosphine to give the corresponding pyrroloquinolines and pyrroloindoles respectively. In the case of an indole-2,7-dicarbaldehyde, reaction at the 2-carbaldehyde is preferred, giving the related pyrroloindole. In the case of a 6-hydroxy-4methoxy-3-substituted-indole-7-carbaldehyde formation of a pyrroloquinoline is preferred to cyclisation on to the phenolic group to generate a pyranoindole. The pyrroloquinolines and pyrroloindoles are highly fluorescent.
“…As yet there appears to be no report of any naturally occurring 6-oxopyrroloquinoline. Synthetic 6-oxopyrroloquinolines 3 utilize one of two general approaches, involving either the construction of a pyrrole ring on to a quinoline by a standard indole synthesis, − or the construction of a new six-membered ring between N1 and C7 of an indole. ,− …”
7-Acetyl-4,6-dimethoxy-3-phenylindole 10 was converted into a range of 7-indolyl chalcones 13 by reaction with aryl aldehydes under basic conditions. Oxidation of the chalcones 13 with alkaline hydrogen peroxide gave the isolable epoxides 14, which were cyclized with further base treatment into the indole flavonols, or 5-hydroxy-6-oxopyrroloquinolines 15. The related compounds 25 and 26, examples of indole flavanones and flavones, respectively, were also synthesized. UV spectroscopic comparisons between flavonoids and indole flavonoids are discussed.
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