Synthesis of Functionalized Quinolines from 4-(o-Nitroaryl)-Substituted 3-Acyl-4,5-Dihydrofurans: Reductive Cyclization and C=C Bond Cleavageстатья
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Дата последнего поиска статьи во внешних источниках: 12 июля 2017 г.
Аннотация:A new synthetic approach to functionalized quinolines was developed based on the application of Zn-AcOH system as a simple and efficient reductive agent towards 4-(o-nitroaryl)-3-acyl-substituted 4,5-dihydrofurans. Reduction of 3-carbonyl-substituted dihydrofurans is accomplished by C=C double bond cleavage in the dihydrofuran ring and 1,6-cyclization leading to 3,4-dihydroquinolines. The latter can be easily oxidized to quinolines or reduced to tetrahydroquinolines. For dihydrofuran-3-carboxylates, reduction proceeds with retention of the dihydrofuran ring and affords a tricyclic dihydrofuroquinoline core under harsher conditions. The proposed general reaction pattern was supported by results of DFT calculations. Moreover, a similar reductive system can be successfully applied in the conversion of dihydrofuran acyclic precursors, -(o-nitroaryl) α,β-unsaturated carbonyl compounds, into quinoline derivatives.