Molecular and crystalline structures of some (3R)-methyl-6(R)-isopropylcyclohexanone 2-arylidene derivatives modified by cyclopropanation

Molecular structures of the series of 1(S)-(4X-phenyl)-5(R)-isopropyl-5Y-8(R)-methyl-3(R)-spiro[2,5]octan-4-ones (Y = H, X = F, Br, C6H5 and Y = CH3, X = Br, C6H5) as main products of the cyclopropanation reaction of the respective 3-methyl-6-isopropyl-6-Y-cyclohexanone 2-arylidene derivatives were studied by the NMR (1H and 13C) spectroscopy and X-ray diffraction analysis. All of compounds studied have the trans–trans configuration (trans-orientation of the aryl and carbonyl groups with respect to each other and trans-position of the substituted cyclopropane –CH2– link with respect to the methyl group at the chiral center of the cyclohexanone ring). Configurations 1(S)3(R)5(R)8(R) were determined for all of the products prepared. Conformation of the cyclohexanone ring with the axial methyl group and equatorial isopropyl one was found to dominate in reaction products similarly to the respective starting enones. Replacement of the CC double bond in the enone compounds with the cyclopropane ring has no effect on bond lengths between the fragments mentioned and the carbonyl or aryl groups.