Nitrogen bridgehead compounds. Part 41. Ring transformation of nitrogen bridgehead ring systems

Abstract

In an investigation of the role of the nitrogen atoms in the ring-transformation reactions of nitrogen bridgehead condensed pyrimidinones (1), either the bridgehead or the non-bridgehead nitrogen atom was replaced by a carbon atom. While replacement of the non-bridgehead nitrogen atom did not influence the ring-transformation reaction, replacement of the bridgehead nitrogen atom prevented the rearrangement. Thus, ethyl 1-cyano-6-methyl-4-oxo-4H-quinolizine-3-carboxylate (10) was transformed into ethyl 8-cyano-5-hydroxy-2-methylquinoline-6-carboxylate (11) at 250 °C. X-Ray crystallographic analysis confirms the structure of (11): monoclinic system with a= 11.385(1), b= 11.102(1), c= 10.191(2)Å, space group P2₁/n, Z= 4, D_c= 1.36 g cm^–3, R= 0.043. The quinoline (11) gave 5-ethoxy-2-methylquinoline-8-nitrile (12) at 260 °C.