Cathylation of 4,6-dimethyl-2-oxopyridine-3-carbonitrile derivatives leading to the synthesis of furo[2,3-b;4,5-b ']dipyridines and novel tricyclic furo[2,3,4-ij][2,7]-naphthyridine

Cathylation of ethyl 2-(3-cyano-4,6-dimethylpyridine-2-yloxy)acetate afford ed a trace amount of new tricyclic furo[2,3,4-ij][2,7]naphthyridine derivat ive. An attempt was made for an alternate method for the synthesis this new tricyclic ring system. Treatment of 4,6-dimethyl-2-oxopyridine-3-carbonitr ile (1) with various alpha-halocarbonyl compounds (such as chloropropanone 1 or I substituted 2-bromoacetophenones) gave a mixture of N- and O-alkylat ed compounds, which were readily converted into indolizines and 2-acetyl-3- amino- or 3-amino-2-benzoylfuro [2, 3-b]pyridines. The 3-aminofuro[2,3-b]py ridine I derivatives were further converted into furo[2,3-b;4,5-b']dipyridi nes, but not the: expected tricyclic furonaphthyridines, via N,O-acetylatio n and cyclization.