Alkyl-1,8-naphthyridines acylation

The N-acylation product of the reaction of enaminones with either 2-chloronicotinoyl chloride or 2,6-dichloro-5-fluoronicotinoyl chloride readily undergoes cyclization (either directly or on treatment with sodium hydride) to give high yields of 8-acyl-7-alkyl[l,6]naphthyridin-5(6//)-ones, which themselves are attractive precursors for elaboration to naphtho[2,3-, ][l,6]naphthyridin-5-ones and pyrido[2,3-f][l,6]naphthyridin-6-ones <2002T58>. 

Such ketones have been made by direct C-acylation of alkyl-1,5-naphthyridines (see Section 2.2.2). 

Note Although simple C-alkylation of 1,6-naphthyridine is rare, concomitant C-alkylation and A-acylations are well represented (see Reissert reactions below). 

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