Michael addition of 2-aminopyridines with methylpropiolate to afforded the addition compound 1 a-g , which on further cyclisation at higher temperature in dowtherm-A to yield cyclised product 2 a-g , with respective yields depends on the nature of the substituents.Key words: Propionoic acid methyl ester, 2-aminopyridine and 3-(Pyridin-2-ylamino)-acrylic acid methyl ester.
Reaction of 2-aminopyridine-3-carbaldehyde with 5,5'-Dimethyl-CycIohexane-l,3-dione afforded 8,8'-dimethyl-8,9-dihydro-7H-benzo[b][l,8]naphthyridin-6-one (1). Friedlander condensation of (1) with 2-aminopyridine-3carbaldehyde yielded 6,6-dimethyl-6,7-dihydro-l,8,9,14-tetraaza-pentaphene (2), in good yield. Bromination of (1)The compound (3) on reaction with one equivalent of [(ethoxycarbonyl)-methylene] triphenylphosphorane (aza-Wittig reaction) gave ethyl 2-(7-bromo-8,9-dihydro-8,8-dimethylbenzo[b][l,8]naphthyridin-6(7H)-ylidene)acetate (4). Further the compound (4) on cyclisation with anilines to provide the cyclised compounds, 3,3a,4,5-tetrahydro-4,4-dimethyl-3-phenylindolo[5,4-b][l,8]naphthyridin-2-one (5a-e).Keywords: 2-aminopyridine-3-carbaldehyde, [l,8]naphthyridin-6(7H)-ylidene)acetate, and amide ring cyclisation.
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