Conformational Analysis of Some trans-4,5-Diaryl-1,3-dioxolanes by CD Spectroscopy and Induction of Cholesteric Mesophases in Nematic Solvents:  A Correlation between Twisting Power and Structure of the Dopant

A series of trans-4,5-diaryl-1,3-dioxolanes (compounds 1−10) has been prepared from the corresponding 1,2-diols obtained by asymmetric syn-dihydroxylation of (E)-olefins, in the presence of derivatives of quinidine. Compounds 1−10, when dissolved in MBBA or E7, induce left-handed cholesterics, showing twisting powers which, in absolute value, are strongly dependent on the structure of the solute and on the nature of the nematic mesophase. By means of molecular mechanics calculations and the analysis of CD spectra of 1−10, it is possible to determine the most stable conformation of these derivatives which is characterized by a negative twist of the aryl moiety. With this information a reliable cholesteric induction model has been developed.