STRUCTURE, CONFORMATION, AND STEREODYNAMICS OF N-NITROSO-2,4-DIARYL-3-AZABICYCLO[3.3.1]NONANES AND NITROSO-2,4-DIARYL-3-AZABICYCLO[3.3.1]NONAN-9-ONES

The variable temperature H-1, C-13, and F-19 NMR spectra were measured for the title N-nitrosamines. The observed unusually law N-N rotation barriers (12-15 kcal/mol) result from a significant deviation of the nitrosamino system from planarity. A pyramidal character of the amino nitrogen was confirmed by the X-ray crystal structures of two compound s and by bathochromic shifts of the n-pi absorption hands in the UV s pectra. The nonplanarity of the nitrosamino moiety is due to the stron g pseudoallylic A((1,3)) strain caused by the steric interaction of th e NNO group with the neighboring aryl substituents fixed in the equato rial positions of the bicyclic skeleton, In addition, the barriers to the C-C rotation of aryl groups were examined at temperatures lower th an required to ''freeze'' the N-N rotation and different Delta G valu es were observed for the aryls oriented syn and anti to the nitroso ox ygen.