Allene-1,3-dicarboxylic acids reduction

Anodic oxidation of N, N.-dimethylaniline in methanol yields the -methoxylated derivative (72), which reacts with substituted alkenes in the presence of Lewis acid to give a wide range of tetrahydroquinolines (e.g. 73).94- The adduct (75) from N-methylaniline and allene-1,3-dicarboxylic acid dimethyl ester (7 ) can be converted into the 4-quinolone (76) on treatment with polyphosphoric acid. 95 The use of nitrobenzenes as quinoline precursors is exemplified by the reaction sequence depicted in Scheme 17. The transition-metal-catalysed transformation is thought to involve the reduction of the nitrobenzene to the corresponding aniline via a nitrene intermediate.96... 

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