A New Class of Chiral Smectic Liquid Crystals: Substituted Biphenylylcyclohexylideneethanones Having an Axial Chirality

Article abstract of DOI:10.1021/jo00221a020

The introduction of chiral cyclohexylideneethanone unit in a potential mesomorphic structure leads to the first family of optically active liquid crystals having an axial chirality.Racemic compounds 2 were synthesized by a Wittig-type coupling between β-keto phosphonates 6 (R1 = n-C5H11) and substituted cyclohexanone 7 (R2 = H, CH3, t-Bu, OCH3, O-n-C5H11, CO2Et, OCOC6H4CN, OCOC6H4Cl).The optically active molecules 12 were prepared by a new route using the asymmetric coupling of a carbanion α to a chiral sulfoxide 9 (R2 = n-C5H11, CH2OEt) and a substituted biphenyl acid chloride (Ar = R'C6H4C6H4 with R' = n-C5H11, CH3O, n-C8H17O, CN) followed by a stereospecific pyrolytic elimination of the sulfoxide moiety.Derivatives containing only one aromatic ring were not mesomorphic in contrast to those having a biphenyl system.