Alexandra Moskal

Conjugated schiff's bases—141: Cycloaddition of heterocumulenes to some 1-oxa-4-azabutadienes

Abstract 1-Oxa-4-azabutadienes proved to be prone to react with some heterocumulenes after 1,3-cycloaddition patterns yielding various 5,5-disubstituted derivatives of 1,3-diaryl-hydanotoins as it was shown by the chemical and spectroscopic analysis. Relatively high yields, mild reaction conditions and a very weak effect of solvent polarity on the reaction rate suggested a synchroneous mechanism involving 1,2-migration of a substituent.

Conjugated schiff's bases—10: Control effect of charge resonance coupling on 1,3-cycloaddition of heterocumulenes to some 1,4-diazabutadienes

Abstract 1,3-Dipolar cycloaddition of organic isocyanates to some 1,4-diazabutadienes has been investigated by theoretical and experimental methods. Analysis of HOMO, LUMO interactions indicated the reaction mechanism and the product structure. Cycloaddition proved to be combined with 1,4 sigmatropic-type hydrogen shift and elimination of the initial 1,4-diazabutadiene fragment.

ConjugatedSchiff bases. 15. substituent effect on the cycloaddition of heterocumulenes to some 1-oxa-4-azabutadienes@@@KonjugierteSchiff-Basen, 15. Mitt.: Substituenteneffekte bei der Cycloaddition einiger Heterocumulene mit 1-Oxa-4-azabutadienen

The substituent effect on the cycloaddition of aryl isocyanates to some 1-oxa-4-azabutadienes has been investigated. It has been found that electron-withdrawing groups located in the aryl isocyanate ring distinctly increase the rate of the cycloaddition. The importance of isocyanate nitrogen unshared electrons has been considered. Rate constants and activation parameters have been discussed with respect to the mechanism.ZusammenfassungDer Substituenteneffekt bei der Cycloaddition von Arylisocyanaten an einige 1-Oxa-4-azabutadiene wurde untersucht. Es wurde festgestellt, daß e-anziehende Gruppen am Aryl-isocyanat-Ring deutlich die Geschwindigkeit der Cycloaddition erhöhen. Geschwindigkeitskonstanten und Aktivierungsparameter werden im Hinblick auf den Reaktionsmechanismus diskutiert.