Crystal structure of 2-p-bromobenzoyl-1,5,5-trimethylbicyclo[2,2,2]-octa-6,8-dione

Abstract

An unexpected product of formula C₁₈H₂₀O₃, obtained by treatment of β-dimethylaminopropiophenone at its boiling point with isophorone, has been shown to be 2-benzoyl-1,5,5-trimethylbicyclo[2,2,2]octa-6,8-dione by a single-crystal X-ray analysis of the p-bromo-derivative. The crystals, of formula C₁₈H₁₉O₃Br, are monoclinic, space group P2₁/c with Z= 4 in a unit cell of dimensions a= 17·71, b= 9·25, c= 10·63 Å, and β= 106·5°. The structure was solved by the heavy-atom method and refined by least-squares calculations to R 0·099 for 1828 reflexions. The elucidation of the structure has yielded further information about the mechanisms of thermal Michael condensations.