DYNAMIC STEREOCHEMISTRY OF N-PHENYL-9-TRIPTYCYLAMINE AND ITS N-ALKYL DERIVATIVES

In N-phenyl-9-triptycylamine (6), ''gear rotation'' (GR) and ''isolate d rotation'' (IR) have almost the same free-energy barriers of ca. 45. 2 kJ mol(-1), while the nitrogen inversion is fast throughout the whol e temperature range and thus the nitrogen is regarded as planar on the NMR timescale. In N-methyl-N-phenyl-9-triptycylamine (7), the interna l motions are fast on the NMR time scale even at the lowest attainable temperature. In N-benzyl-N-phenyl-9-triptycylamine (8), the GR proces s has a free-energy barrier of ca. 36 kJ mol(-1) and the passing of th e benzyl group over an o-benzeno group has a higher barrier than GR. N -2-Biphenylyl-9-triptycylamine (9), which is obtained during the cours e of the synthesis of 6, shows a dynamic behavior presumably ascribabl e to GR with the free-energy barrier of 70 kJ mol(-1).