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Nitrogen Bridgehead Compounds. Part 42. Cyclization of Diethyl 2-(2-Pyridylaminomethylene)-succinates and -glutarates in Ethanolic Sodium Ethoxide
Vasvari-Debreczy, Lelle,Hermecz, Istvan,Meszaros, Zoltan
, p. 1799 - 1804 (2007/10/02)
2-(Pyridylaminomethylene)-succinates (1) and -glutarates (2) were treated with ethanolic sodium ethoxide solution.The succinates (1) gave, in reversible reactions, pyridopyrimidines (3) and pyridylpyrrolinones (5), and also underwent Z-E geometric isomerization.The cyclizations (Z)-(1) to (3) and (E)-(1) to (5) were more rapid than the isomerization of (1).Thus, short (1-min) reactions starting from (Z)-(1) produced the pyridopyrimidine (3) and those from (E)-(1) the pyridylpyrrolinone (5) in good yield.Longer (15-min) reactions yielded equilibrium mixtures, consisting mainly of pyridylpyrrolinones (5).Substituents at position 6 of the pyridine ring inhibited the formation of the pyridopyrimidines, whereas those at position 3 hindered or inhibited the formation of the pyridylpyrrolinones.The unsubstituted glutarate (2a) formed the pyridopyrimidine (4a) whereas the 6-substituted ones did not yield any cyclic product.Results of the sodium ethoxide ring closure were compared with those of the previously studied POCl3 - PPA and thermal cyclizations.
