Torsional effects on the conformations of two diastereomeric tetracyclic bis(hydrazines)
摘要:
The symmetrical tetraazatetracyclotetradecadiene (1) is bis(tert-butylated) (tert-butyl alcohol/H+) and bis(methylated) (methyllithium) to a 1:1 mixture of diastereomeric 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(s) 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. AM1 calculations carried out using VAMP both predict this result and show it to be caused by tetracyclic ring torsion (experimentally approximately 12.7-degrees about the central CC bond for crystalline 9a, approximately 13.2-degrees for 9s).
Torsional effects on the conformations of two diastereomeric tetracyclic bis(hydrazines)
作者:Stephen F. Nelsen、J. Jens Wolff、Hao Chang、Douglas R. Powell
DOI:10.1021/ja00021a009
日期:1991.10
The symmetrical tetraazatetracyclotetradecadiene (1) is bis(tert-butylated) (tert-butyl alcohol/H+) and bis(methylated) (methyllithium) to a 1:1 mixture of diastereomeric 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(s) 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. AM1 calculations carried out using VAMP both predict this result and show it to be caused by tetracyclic ring torsion (experimentally approximately 12.7-degrees about the central CC bond for crystalline 9a, approximately 13.2-degrees for 9s).