Beilstein J. Org. Chem.2011,7, 980–987, doi:10.3762/bjoc.7.110
the starting tetrahydroquinoline, such as O-, N- and C-linked residues (Scheme 2) [8][9][12][13][16][17][18]. Unfortunately, the alternative oxidation–elimination products (5 and 8) are often observed, therefore suggesting an acid catalyzed process. This would account for the elimination of alcohol
, commercial reagents and additives on the oxidation of an elimination-prone Povarov tetrahydroquinoline substrate.
In this way, tetrahydroquinolines 17,17' were synthesized as a mixture of isomers from the enol ether 14, p-bromoaniline (15) and p-chlorobenzaldehyde (16) under Sc(OTf)3 catalysis using standard
]+ calcd for C18H16BrClNO, 376.0098; found, 376.0090.
Optimization of the reaction conditions for the preparation of quinoline 18.
Povarov oxidation access to substituted quinolines.
Tetrahydroquinoline oxidation.
Synthesis of the Povarov adducts and their oxidation products.
Oxidation of lactam-fused
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Graphical Abstract
Scheme 1:
Povarov oxidation access to substituted quinolines.
Beilstein J. Org. Chem.2011,7, 298–303, doi:10.3762/bjoc.7.39
Discussion
The tetrahydropyridones employed in this study were prepared according to published procedures with slight modifications. In particular, oxidation of the tetrahydroquinoline 5 with oxone [38] afforded the nitrone 6 [39][40][41] in 66% yield (Scheme 2, see Supporting Information File 1 for full
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Graphical Abstract
Scheme 1:
General approach to spirocyclopropanated tetrahydropyridones by 1,3-dipolar cycloaddition/thermal r...