(2-Pyridyl)iminopropadienone

Abstract

(2-Pyridyl)iminopropadienone 13 is generated by flash vacuum thermolysis (FVT) of 2-substituted pyrido[1,2-a]pyrimidin-4-ones 9 and observed by IR spectroscopy. Addition of HCl to 13 causes reversion to the starting material 9b, whereas addition of nucleophiles leads to malonic acid imide derivatives (23, 24, 26, 27, 28). The latter undergo thermal elimination of amines to regenerate 2-substituted pyridopyrimidinones. A competing retro-ene reaction occurs on FVT of 2-(dialkylamino)pyridopyrimidinones 9c,d, presumably in the oxoketenimine intermediates 22/25, with formation of the unsubstituted pyridopyrimidinone 31.