Recently, we have reported the synthesis of quinoline ring system by an intermolecular [4+2] cycloaddition of the Schiff base as a diene with the styrene derivative as a dienophile. It is thus of interest to examine the further application of the above cycloaddition employing cyclic enol ether as a dienophile to construct a fused quinoline ring system, not only for investigation of its extension, but also because of the occurrence of a number of physiologically interesting quinoline alkaloids as natural products.
