Liquid-Crystalline Solvents as Mechanistic Probes. 20. Crystalline and Smectic B Solvent Control over the Selectivity of Photodimerization of n-Alkyl Cinnamates

Article abstract of DOI:10.1021/jo00363a025

The photodimerizations of n-octadecyl, n-hexadecyl, and n-tetradecyl esters of trans-cinnamic acid have been investigated in the crystalline, smectic B, and isotropic phases of n-butyl stearate.A strong preference for head-to-tail dimerization is found in the ordered solvent phases.Dipole-dipole-induced interactions between cinnamates and solvent-mediated solute alignments are the factors that combine to control the regioselectivity of photodimerization.The ability of cinnamate esters to be incorporated into the ordered solvent phases is extremely dependent upon the length of the n-alkyl solute chains.However, ease of incorporation has little influence upon regioselectivity.