Conformational and configurational studies on 3‐azabicyclo[3.3.1]nonane (3‐abn) derivatives and related systems employing carbon‐13 NMR spectroscopy

The 13C nmr spectra of 4 cis‐2,4‐diphenyl‐3‐azabicyclo[3.3.1]nonanes, 11 cis‐2,4‐diaryl‐3‐azabicyclo[3.3.1]‐nonan‐9‐ones, 26 cis‐2,4‐diaryl‐3‐azabicyclo[3.3.1]‐nonan‐9‐ols or acetates thereof, 5 cis‐2,4‐diaryl‐3‐azabi‐cyclo[4.3.1]decan‐10‐ones or ‐10‐ols and 5 cis‐2,4‐diphenyl‐3‐aza‐7‐thiabicyclo[3.3.1]nonan‐9‐ones, ‐9‐ols or 9‐yl acetates have been recorded. Except for the 7‐thia compounds, which appear to exist mainly in the configuration and conformation with the nitrogen‐containing ring in the boat form, these compounds seem to exist overwhelmingly in chair‐chair conformations. The configuration of the 9‐ols and their acetates (syn or anti to the nitrogen‐containing ring) has been deduced from the spectra. In a number of cases, the structures assigned differ from those earlier postulated. Broadening of one set of aryl signals (probably those due to the ortho carbons) in the case of N‐methyl (but not N‐H) compounds without ortho substituents is ascribed to restricted phenyl rotation.