A new approach to the synthesis of polyfunctionally substituted 1,8-naphthyridin-2-one derivatives from 6-azidopyridones: A novel thermal decomposition to 6-aminopyridones

Azidation of the chloroaldehyde 2, which was obtained from the 6-hydroxy-2- pyridones 1, afforded the 6-azido-2-pyridones 3. Compound 3 can be converte d to the corresponding 6-amino-2-pyridones 5, by the reaction with tripheny lphosphine via phosphazenes and subsequent hydrolysis (Staudinger reaction) . This obtained amine 5 reacts with ethyl cyanoacetate in an ethanolic solu tion containing piperidine to give 7-amino-6-carbethoxy-3-cy ano-1,4-dimeth yl-1,8-naphthyridin-2(1H)-one (9), Reaction of 9 with dimethylformamide dim ethyl acetal, triethylorthoformate and hydrazine hydrate furnished the new 1,8-naphthyridin-2-ones 10, 11 and 12. respectively, in good yields. On the other hand, refluxing 9 with piperidine or morpholine, as secondary amines , did not afford the corresponding 1.8-naphthyridin-2-ones 13, but instead it undergoes a thermal decomposition under these reaction conditions to yie ld the unexpected 6-amino-3-cyano-1,4-dimethyl-pyridin-2(1K)-one (14).