Thermolysis, at ca. 110 °C, of the strained norbornane furazan N-oxides (5)–(8) in toluene, saturated with sulphur dioxide, affords the isomeric 1,3-di-isocyantocyclopentanes (14)–(17). Product formation is explained by a mechanism involving cleavage of the furazan ring to cyclopentane-1,3- bis(nitrile oxides)[e.g.(9)], followed by 1,3-dipolar cycloaddition with SO2 to form bis-1,3,2,4-dioxathiazol-2-ones [e.g.(12)]. Subsequent extrusion of SO2 and rearrangement yields di-isocyanates [e.g.(14)] which were identified spectroscopically and by preparation of urethane and/or urea derivatives on reaction with alcohols and aniline. Compound (8) with aniline gives the cyclic biuret (20) rather than a bis-urea, the structure of the product being established by X-ray crystallography. In the absence of SO2 polymeric furoxans are formed.

AbstractThermolysis of the strained furoxans (Ia) to (Ic) in toluene saturated with SO2 yields the 1,3‐di‐isocyanato‐cyclopentanes (IVa) to (IVc).

AbstractDas Furazanoxid (V) wird ausgehend von Norbornen (I) durch Behandlung mit N2O3, thermische Isomerisierung des Nitronitroso‐Addukts (II) zum Nitro‐oxim (IV) und nachfolgende Dehydratisierung synthetisiert.

AbstractAus Cyclopentandion (I) wird das Dioxim (II) synthetisiert, dessen oxidative Cyclisierung mit NaOCl im alkalischen Medium bei niedriger Temp. zu dem Trimethylenfurazan‐N‐oxid (III) (Raumgruppe Pbca Z=8) führt; beim Destillieren bei 150°C (Badtemp) unter Normaldruck zersetzt sich (III) explosionsartig.

AbstractDie Furoxane (I), (III) und (V) ergeben beim Erhitzen in mit Schwefeldi‐ oxid gesättigtem Toluol die Diisocyanate (II), (IV) und (VI).

Thermolysis of strained furazan N-oxides of the norbornane series results in fragmentation of the oxadiazole ring, the isolated products being di-isocyanates when the reactions are carried out in the presence of sulphur dioxide, while in its absence unstrained polymeric furoxans are formed.