Photoextrusion von molekularem Stickstoff aus 5-Alkyliden-4,5-dihydro-1H-tetrazolen mit Vinyl- oder Phenyl-Substituenten. (E)-Aziridinimine und neuartige Produkte

Photoextrusion of Molecular Nitrogen from 5-Alkylidene-4,5-dihydro-1H-tetrazoles Substituted by Vinyl or Phenyl Groups. (E)-Aziridinimines and Novel Products[1] Direct irradiation of deuterated hydrocarbon solutions of the alkylidenedihydrotetrazoles 11 affords quantitative yields of the aziridinimines (E)- and (Z)-12, besides molecular nitrogen, with (E)/(Z) ratios ranging from 95:5 (12e, -40°C) to >99:<1 (12 c, 20°C). From 14, which carries two different groups at the nitrogen atoms, equal amounts of the isomers 13 and 15 are obtained, again with a strong predominance of the (E) diastereomers. The structures of the aziridinimines have been elucidated by their NMR spectra and, in the case of 13 and 15, by [2 + 1] photocycloreversion into the corresponding isocyanides 16 and imines 17, which is induced by selective irradiations with light of shorter wavelengths. Photolysis of the alkenlidenedihydrotetrazole 18c at -40°c affords the 2-imino-3-vinylaziridine 20c which decomposes at higher temperatures. Irradiation of 18c at 20°C or partial photolysis at -40°C followed by warming to 20°C furnishes the spirocyclic product 19c. The analogous products 19a and b are obtained from 18a and b. The vinyl compound 19a very slowly isomerizes to the ethylidene compound 23 by a proton 1,3-shift. The spirocyclic structures 19 and 23 are based on mass and NMR spectra including 1H,1H and 13C1H COSY and extensive 1,1H decoupling experiments. The formation of the spirocycles 19 is interpreted in terms of a photoextrusion of molecular nitrogen from 18 to afford 3-vinylaziridinimines 20 which, at higher temperatures, rearrange to the 1,3-diazabutadienes 24 by a hydrogen homo[1,5]- or homo[1,7]-shift. [4 + 2] Cycloaddition of 24 to unchanged 18 eventually yields the spirocycles 19.