SYNTHESIS, STRUCTURE (NMR AND MASS-SPECTROMETRY) AND CONFORMATIONAL-ANALYSIS OF HETEROCYCLIC-ANALOGS OF DIBENZO[A,E]CYCLOOCTA-1,5-DIENE - 5,6,12,13-TETRAHYDROBISPYRAZOLO [1,2-A-1',2'-E][1,2,5,6] TETRAAZOCINEDIIUM DIHALIDES

Several spyrazolo[1,2-a:1',2'-e][1,2,5,6]tetraazocinediium dihalides 4 a-d and 8 are prepared from pyrazole, 3,5-dimethylpyrazole, 4-(1-adama ntyl)pyrazole and campho[2,3-c]pyrazole by stepwise alkylation with 1, 2-dibromoethane or 1,2-dichloroethane, Their structural characterizati on has been achieved by NMR and mass spectrometry. Dynamic NMR spectro scopy allowed the measurement of the barrier for the chair-chair inter conversion in the case of the parent compound 4a and the 1,3,8,10-tetr amethyl derivative 4b, These barriers as well as the preferred chair c onformation are rationalized through semi-empirical and molecular mech anics calculations with regard to dibenzo [a,e]cycloocta-1,5-diene. Th e study of doubly charged bispyrazolium salts allows demonstration of their reduction by addition of a hydride ion [C++ + H- --> (C + H)(+)] during FABMS experiments.