Synthesis, characterization and stereochemistry of N-acyl-r-2,c-4-bis(4-methoxyphenyl)-3-azabicyclo[3.3.1]nonanes

• Four N-acyl-2,4-bis(4-methoxyphenyl)-3-azabicyclo[3.3.1]nonanes were synthesized.
• Assignments of 1H & 13C NMR signals are made using 2D NMR spectra.
• They prefer twin-chair conformation with partial flattening at nitrogen end.
• Anisyl groups occupy quasi-axial orientation to avoid A1,3-strain.
• X-ray crystal structure also supports the solution state conformation.

Four new N-acyl-2,4-bis(4-methoxyphenyl)-3-azabicyclo[3.3.1]nonanes 3–6 have been synthesized. The structural characterization and the conformational preferences of the compounds 3–6 have been carried out using IR, 1D and 2D NMR and Mass spectral data. The NMR spectral data indicates that the N-acyl-2,4-bis(4-methoxyphenyl)-3-azabicyclo[3.3.1]nonanes 3–6 prefer to exist in twin-chair conformation with partial flattening at nitrogen end. To avoid A1,3-strain, the anisyl groups at C2 and C4 are forced to occupy the quasi-axial orientation. X-ray crystal structure of the N-dichloroacetyl-2,4-bis(4-methoxyphenyl)-3-azabicyclo[3.3.1]nonane 6 also supports the similar conformation in the solid state.

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