6‐Substituted 1,6‐naphthyridine‐5(6H)‐ones were prepared from diethyl 2‐[2‐(dimethylamino)vinyl]‐6‐methylpyridine‐3,5‐dicarboxylate 1  by ring closure with aromatic and heteroaromatic diamines (o‐phenylenediamine, 2,3‐diaminopyridine, 3,4‐diaminopyridine and 4,5‐diaminopyrimidine, respectively). 1,6‐Naphthyridine‐5(6H)‐ones were cyclised in phosphoryl chloride to yield nitrogen bridgehead tetracycles 6‐9. The structure of the products was established by nOe difference spectroscopy. A complete 1H and 13C nmr assignment was achieved by different 2D carbon‐proton correlation measurements.
ASJC Scopus subject areas
- Organic Chemistry