Cooperative effects in restricted rotations of aryl groups in 2,4,6,8-tetraary-3,7-diazabicyclo[3.3.1]nonanes and related systems |
| |
Authors: | Lloyd M. Jackman Theresa S. Dunne Jan L. Roberts Bodo Mūller Helmut Quast |
| |
Affiliation: | 1. Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, U.S.A.;2. Institut für Organische Chemie der Universität Würzburg, Am Hubland, D-8700 Wurzburg, F.R.G. |
| |
Abstract: | The free energies, enthalpies and entropies of activation for the rotation of the aryl groups in the N,N′-dimethyl and N,N′-dichloro derivatives of rel-(2R,4S,6S,8R)-2,4,6,8-tetrakisaryl-3,7-diazabicyclo[3.3.1]nonanes have been determined and compared with related tricyclic systems which cannot undergo chair-to-boat conformational changes. It is concluded on the basis of the large, negative value of ΔS3 for rotation of the 2(4) aryl group that this rotational process is correlated with rotation of the 8(6) aryl group. The 8(6) aryl group can however rotate independently of the 2(4)-aryl group. The usefulness of the entropies of activation as a criterion for cooperative rotation of groups is briefly discussed. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|