Studies on quinoline derivatives and related compounds. III. A novel pyridine synthesis to give substituted 1,4‐dihydro‐4‐oxonicotinic acids

A variety of 5‐mono‐ and 5,6‐disubstituted 1,4‐dihydro‐4‐oxonicotinates were prepared by a novel pyridine synthesis which involves thermal cyclisation of enaminomethylenemalonates 9. The intermediates 9 were readily prepared through a few steps from commercially available starting materials.