Reduktion von 1,2‐bis[( Z )‐(2‐nitrophenyl)‐ NNO ‐azoxy]benzol : Synthese von Cyclotrisazobenzol ( = (5 E ,6a Z ,11 E ,12a Z ,17 E ,18a Z )‐5,6,11,12,17,18‐Hexaazatribenzo[ aei ][1,3,5,7,9,11]cyclododeca‐hexaen)

Reduction of 1,2‐Bis[( Z )‐(2‐nitrophenyl)‐ NNO ‐azoxy]benzene 1 : Synthesis of Cyclotrisazobenzene ( = (5 E ,6a Z ,11 E ,12a Z ,17 E ,18a Z )‐5,6,11,12,17,18‐Hexaazatribenzo[ aei ][1,3,5,7,9,11]cyclododeca‐hexaene) Na 2 S reduction of 1,2‐bis[( Z )‐(2‐nitrophenyl)‐ NNO ‐azoxy]benzene ( 2 ) yielded 3 deoxygenated products: the (known) red 2,2′‐(( E , E )‐1,2‐phenylenbisazo)dianiline ( 3 , 23%), the orange 2‐[2‐(( E )‐2‐aminophenylazo)phenyl]‐2 H ‐benzotriazol ( 4 , 55%) and the colorless 2,2′‐(1,2‐phenylene)di‐2 H ‐benzotriazol ( 5 , 13%). The constitutions of 3 – 5 and of 6 , the N ‐acetyl derivative of 4 , were deduced from their 1 H‐NMR spectra (chemical shifts, couplings, and symmetry properties), and the configurations of 3 , 4 , and 6 at their N,N‐double bonds are assumed to be the same as in 2 . Oxidation of 3 with 2 mol‐equiv. of Pb(OAc) 4 afforded 5 (47%) and a novel, highly symmetrical macrocycle, called cyclotrisazobenzene ( 7 , 24%). The constitution of 7 as a tribenzo‐hexaaza[12]annulene and its ( E )‐configuration at the N,N‐bonds was confirmed by X‐ray analysis. The molecular symmetry expressed by the 1 H‐, 13 C‐ and 15 N‐NMR spectra of 7 reveals a rapid torsional motion around the six N,C bonds. This implies that the N,N‐double bonds in the cyclic 12π‐electron system (or 24π‐electron system if the benzene rings are included) of 7 are highly localized.