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‐1 H ‐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 alk en lidenedihydrotetrazole 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 1 H, 1 H and 13 C 1 H COSY and extensive 1 , 1 H 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 .