STEREOCHEMISTRY OF ACETYL-R-2,C-4-DIPHENYL-3-AZABICYCLO[3.3.1]NONANESAND ARBONYL-R-2,C-4-DIPHENYL-3-AZABICYCLO[3.3.1]NONANE

The conformational preferences of -acetyl-r-2,c-4-diphenyl-3-azabicycl o[3.3.1]nonane 3 and N-ethoxycarbonyl- and t-6,t-8-tetraphenyl-3,7-dia zabicyclo[3.3.1]nonanes 6 and 7 have been studied using NMR spectral t echniques. The azabicyclo[3.3.1]nonane 3 is found to prefer a twin-cha ir conformation with a slight flattening at the nitrogen end. In the c ase of diazabicycles 6 and 7 both the ethoxycarbonylation and acetylat ion reactions are found to take place only at the boat end of the pare nt amine and the preferred conformation of the products is found to be twin-chair with flattening at C-1-C-2-N-3-C-4-C-5 part of the ring in both cases. The energy barrier for the N-CO rotation in N-ethoxycarbo nyl derivative 6 has been determined from the dynamic H-1 NMR studies and the barrier for N-CO rotation is found to be 50.8 kJ mol(-1), much less than that of N-nitroso analogues.