Molecular conformations. Part XI. A boat-chair bicyclo[3,3,1]nonane: crystal structure analysis of 9-benzoyl-3α-bromo-9-azabicyclo[3,3,1]-nonan-2-one

Abstract

The molecular dimensions of 9-benzoyl-3α-bromo-9-azabicylo[3,3,1]nonan-2-one, a bicyclo[3,3,1]nonane with the boat-chair conformation, have been determined by X-ray crystal-structure analysis. Comparison with results previously obtained for the 2-hydroxy-analogue and for various twin-chair bicyclo[3,3,1]nonanes shows that the boat-chair compounds deviate less from ideal cyclohexane ring geometry than the twin-chair compounds. A notable distortion of the valency angles at C(2) in the bicyclononan-2-one demonstrates a pronounced repulsion between the carbonyl group and the adjacent 3-bromo-substituent. The bicyclononan-2-one crystallizes in the monoclinic space group P2₁/c, with a= 10·066, b= 10·459, c= 13·753 Å, β= 105·5°, and Z= 4. The atomic co-ordinates were deduced by a Patterson superposition method and adjusted by least-squares calculations, the final value of R being 10·1% over 1120 reflections.