Synthesis of heterocycle-annelated Naphthyridones with a bridgehead nitrogen atom

Synthesis of a [b]-fused [2,6]naphthyridone

To further demonstrate the versatility of this method, a representative of a [b]-annelated [2,6]-naphthyridone (compound 19) was also prepared, starting from ethyl 3-bromoisonicotinoate (18) [11,12] and (1-methyl-2-benzimidazolyl)acetonitrile [4].