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.