Über 3,3,6,9,9‐Pentamethyl‐2,10‐diaza‐bicyclo‐[4.4.0]‐1‐decen und einige seiner Derivate. Über synthetische Methoden. 13. Mitteilung

3,3,6,9,9‐Pentamethyl‐2,10‐diaza‐bicyclo[4.4.0]‐1‐decen and some of its derivatives A simple synthesis for the bicyclic amidine 1 ( Scheme 3 ) is described. This base and the salts which were prepared from it show solubility characteristics which make the amidine a potentially useful reagent for salt formation of carboxylic acids and related proton complexes of bidentate ligands. Among the derivatives made from 1 are the sterically strongly hindered N ‐alkylated amidines 11 , 12 and 14 ( Scheme 5 ), as well as the stable crystalline N 1 ‐oxidoamidine‐ N 2 ‐oxyl radical 2 ( Scheme 6 ). The ability of the latter to serve as a paramagnetic chelating ligand for metal ions is illustrated by the preparation of a corresponding nickel(II) complex. The radical is also a source for the α‐nitronyl‐nitrosonium cation 4 which shows in its reactivity towards conjugated dienes and olefines some of the expected resemblance to singlet oxygen.