In-Line Proximity Effects in Extended 7-Azanorbornanes. 2. A Major Reduction of N-Inversion Barriers in Symmetrically Flanked Systems.
Through-space compression effects from a pair of flanking (sentinel) groups X are shown to cause a flattening of the bridging nitrogen in symmetrically fused 7-azanorbornanes which is evaluated by a substantial reduction of the nitrogen inversion barrier as measured by low-temperature (1)H NMR spectroscopy. This effect is attributed to destabilization of the ground state of the amine.
Malpass
JR
Department of Chemistry, University of Leicester, Leicester, United Kingdom, LE1 7RH, and Centre for Molecular Architecture, Central Queensland University, Rockhampton, Queensland, Australia, 4700.
Butler
DN
Johnston
MR
Hammond
ML
Warrener
RN