Molecular and crystal structures of chiral 2-(4-phenylbenzylidene)-3-methyl-6-isopropylcyclohexanone 6-bromo derivative

The molecular and crystal structures of chiral 3R, 6S-2-(4-phenylbenzylidene)-3-methyl-6-bromo-6-isopropylcyclohexanone C₂₃H₂₅BrO (Ia) are determined by X-ray diffraction. Crystals Ia are monoclinic, a = 11.005(4) Å, b = 12.229(4) Å, c = 14.376(5) Å, β = 91.37(1)°, Z = 4, and space group P2₁. The geometric parameters of two crystallographically independent molecules are close to each other in magnitude. The cyclohexanone ring adopts a chair-type conformation with an equatorial isopropyl substituent and an axial orientation of the methyl group and the C-Br bond. The 3,6-alkyl groups are in the cis position with respect to the cyclohexanone ring. It is demonstrated that, in the series of 6-bromo substituted compounds, as in their analogues unsubstituted for bromine in the 6-position, the maximum flattening of the cinnamoyl fragment O=C-C=C-C₆H₄ X is observed in the structure with X = C₆H₅.