Reactions of Tautomeric 1,5-Naphthyridinones and the Like

The reductive deoxygenation (Section 2.1.1) and halogenolysis (Section 3.1.2) of such naphthyridinones have been covered already. Their other reactions are illustrated in the following examples. 

3-Benzyl-4-hydroxy-1,5-naphthyridin-2( 1 //)-one (14) (or tautomer) gave a single o- or iV-monoacetyl derivative of indeterminate structure (no details).760 

5-Acetyl-l-benzyl-3,4,4a,5,6,7-hexahydro-l,5-naphthyridine-2,7(l//)-dione (15) (a byproduct from a primary synthesis) appears to have undergone partial dehydrogenation and N— (9-transacylation to afford 7-acetoxy-l-benzyl-3,4-dihydro-1,5-naphthyridin-2( 1 //)-one (16) (Pd/C, xylene, 130°C, 30 h  

Note The alkylation of tautomeric 1,5-naphthyridinones usually gives /V-alkyl derivatives, but (9-alkylation has been achieved by treatment of the substrate silver salt with an alkyl halide the other likely route to (9-alkylation, treatment with an diazoalkane, has not been used in this series. 

The silver salt (17) of 3-nitro-1,5-naphthyridin-2(l//)-one gave 2-ethoxy-3-nitro-l,5-naphthyridine (18) (neat EtI, reflux, 2 h 20%).837 

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