Regiospecific synthesis and structural study of some trifluoromethyl substituted dibenzosemibullvalenes

摘要

Preparation of the regiospecifically trifluoromethyl substituted dibenzosemibullvalenes3and5is described. An unequivocal proof of chirality of3and5was obtained by enrichment of their enantiomers using liquid chromatography on triacetyl- or tribenzoylcellulose. The stereostructure of compounds3to5was proved by their1H-NMR spectra and confirmed by X-ray crystallographic analysis. The geometrical data from X-ray structural analyses showed that five-membered rings involved in the skeleton of3and5adopt flattened envelope conformations. These results indicate also a significant substituent-induced bond length asymmetry in the cyclopropane rings of3and5.