LAUSR

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, which leads 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, γ-(o-nitroaryl) α,β-unsaturated carbonyl compounds, into quinoline derivatives.