Microwave-mediated reactions of 3-aminomethylpyridines with acetylenedicarboxylates. A novel synthetic route to dihydronaphthyridines and naphthyridine-1-ones

Reaction of 3-(1-alkylamino)pyridines with electron deficient acetylenes in the presence of acids yields 1,2-dihydro[2,7]naphthyridine-3,4-dialkyldicarboxylates 4 in 35–72% yield. Compounds 4 unsubstituted in position 1 can be easily oxidized with potassium permanganate into the respective naphthyridine-1-ones derivatives 5 in good yields.