Torsional Effects on the Conformations of Two Diastereomeric Tetracyclic Bis(hydrazines)

Article abstract of DOI:10.1021/ja00021a009

The symmetrical tetraazatetracyclotetradecadiene (1) is bis(tert-butylated) (tert-butyl alcohol/H⁺) and bis(methylated) (methyllithium) to a 1:1 mixture of diastercomeric bis(tert-butylmethylhydrazines) with like alkyl groups anti (9a) and syn (9s). 9a has the expected C₂ symmetry on the NMR time scale (both tert-butyl groups are directed away from the central CC bond, conformation Oi.Oi in Scheme II). 9s does not have the expected C, symmetry, but has one tert-butyl group directed away from the central CC bond and one directed toward it (conformations Oi.oI and Io.iO in Scheme II). Both diastereomers also crystallize in these conformations. AM 1 calculations carried out using VAMP both predict this result and show it to be caused by tetracyclic ring torsion (experimentally ～ 12.7° about the central CC bond for crystalline 9a, ～ 13.2° for 9s).