Molecular Rods: Synthesis and Properties

Article abstract of DOI:10.1021/jo00046a034

Our earlier synthetic methodology affording bicyclo<2.2.2>octyl <1>-rod and <2>-rod systems proved inadequate for <4>-rods.New synthetic approaches were developed, and <3>- and <4>-rod molecules were obtained.Sodium-potassium coupling was employed to afford the longer rod units.A radical anion approach gave lower yields.Hybrid rods with aromatic rings interposed were also synthesized.Rods of 9.2-, 9.7-, 13.4-, 13.9-, and 18.2-Angstroem length were included in this study.Consideration of rod chirality suggests each bicyclooctane rod unit to be stereogenic, either P (clockwise) or M (anticlockwise).Thus, in a <1>-rod there are enantiomers and in a <2>-rod there are diastereomers.Molecular mechanics treatment of rod stereoisomerization was carried out.Interconversion of enantiomers of the <1>-rod and diastereomers of the -rods should be very rapid at room temperature.X-ray analysis of the 4,4'-dimethoxy-<2>-rod reveals an achiral conformation.AM1 quantum mechanics computations were carried out on -rod radical cations and bridgehead cations.