Synthesis of Substituted 1,2‐Dihydro‐2‐imino‐7‐methyl‐1,6(6<i>H</i>)‐naphthyridin‐5‐ones

Abstract

Abstract Vilsmeier formylation of the 4‐amino‐2‐pyridinones 4a–d leads to the formation of the corresponding 3‐carbaldehydes 5a–d (the diformylated product 8 is isolated as a by‐product). A cyclizing Knoevenagel reaction of 5 with CH‐acidic nitriles 6 in the presence of piperidine gives substituted 2‐imino‐1,6(6 H )‐naphthyridin‐5‐ones 7a–p which have been shown by means of 1 H‐NMR and 1 H‐NOE measurements not to rearrange to 9 . The products 7 are resistant against hydrolysis and only the ester group can be hydrolysed to an acid, 7q . Compounds 7c, d, f display in vitro antituberculosis activity.