Pyridine-2-carbaldehydes, 6-substituted synthesis

Numerous 3-(2-cyanovinyl)-substituted 1,8-naphthyridines 392 were prepared by refluxing l,8-naphthyridine-3-carbaldehydes 393 with substituted acetonitriles in alcohol in the presence of catalytic amounts of pyridine. Compounds 392 were covered by a patent as promising starting compounds for the synthesis of new drugs for the treatment of cancer, psoriasis and atherosclerosis (1996FRP2706898). 

A modification of the Westphal synthesis is based on 2-substituted pyridines 18. They are obtained by (9-acylation of the aldol adducts 17 obtained from pyridine-2-carbaldehyde and methylene ketones. The pyridines 18 are quatemized with bromoacetic ester or bromoacetonitrile to 19, followed by base-catalysed cyclization giving 2,3,4-trisubstituted quinolizinium ions 20 ... 

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