Transformations of 2‐aryl‐4‐(2‐oxopyrrolidinyl‐1)‐1,2,3,4‐tetrahydroquinolines, cycloadducts of the BiCl₃‐catalyzed three‐component Povarov reaction: Oxidation and reduction processes towards new potentially bioactive 2‐arylquinoline derivatives

Abstract

Synthesis and spectral characterization of new series of 2-aryl-4-(2-oxopyrrolidinyl-1)-1,2,3,4-tetrahydroquinolines and their aromatic analogs, 2-arylquinolines are reported. It was found that substituted tetrahydroquinoline precursors are easily prepared using BiCl 3 -catalyzed three-component Povarov reaction between 4-nitrobenzaldehyde or 2-naphtylcarboxyaldehyde, anilines and N-vinylpyrrolidin-2-one, and could be transformed via oxidation and reduction processes into potentially bioactive 2-arylquinoline derivatives, unsubstituted at the C-4 position. The all set of (tetrahydro)quinolines were characterized by IR, 1 H and 13 C-NMR spectroscopy.

Asymmetric Synthesis of Tetrahydroquinolines with Quaternary Stereocenters through the Povarov Reaction

“…It would appear that the electron-donating substituent on the aromatic imine enriches the electron density and thus decreases the reactivity. In the case of imines derived from methyl-substituted benzaldehydes, moderate to good yields with excellent diastereo-and enantioselectivities (94-99 % ee) could also be obtained (Table 4, entries [10][11][12]. When an electron-donating 4-methoxy-substituted imine was used, excellent enantioselectivity (98 % ee) was observed, but the yield was substantially reduced ( Table 4, entry 13).…”

“…[9h] However, the previous studies could only afford chiral tetrahydroquinolines with a tertiary stereocenter at the C4 position, and the construction of chiral tetrahydroquinolines with a quaternary stereocenter at the C4 position remains unreported. [10] With a-alkyl styrenes as dienophiles, the corresponding tetrahydroquinoline adducts can be oxidized into quinoline-3-one derivatives with the quaternary carbon center maintained; [11] comparatively, tetrahydroquinolines with the C4 position as a tertiary stereocenter would be converted into quinolines [12] (Scheme 2). With the consideration that tetrahydroquinolines with the C4 position as a quaternary stereocenter potentially exhibit biological activities, an effective catalyst for this Povarov reaction is highly desirable.…”

Multicomponent reaction access to complex quinolines via oxidation of the Povarov adducts

“…The same trend (oxidation–fragmentation) can be observed using nitrobenzene [21] as the oxidant. Analogously, elemental sulfur and palladium, although requiring drastic conditions, also lead to the fragmented quinolines when the substrates bear O- and N-substituents [22–25] (for related isoquinoline oxidations, see [26–27]).…”

Preparación simple de nuevas N-(6-metil-2-nitrofenil-1,2,3,4-tetrahidroquinolin-4-il) pirrolidin-2-onas y su análisis espectroscópico. Objetivos.

“…Based on our experience in the construction of diverse heterocycles containing nitrogen via multi-component Povarov reaction (14)(15)(16), the preparation of the selected tetrahydroquinoline compounds 5,6 was achieved using the BiCl 3 -catalyzed three-component imino Diels-Alder cycloaddition between toluidine 1, nitrobenzaldehydes 3,4 and N-vinylpyrrolidin-2-one 2 (Figure 1).…”