Preparation of (-)-(M)-Paracyclophanohexahelicene from (-)-(M)-1,4-Dimethylhexahelicene and the Absolute Configuration of 4-Substituted Paracyclophanes

Article abstract of DOI:10.1021/jo00323a002

Photocyclization of a cis-trans mixture of the 1,2-diarylethylene precursor 9 gives 1,4-dimethylhexahelicene (10).The levorotatory enantiomer of 10 with M helicity is converted to (-)-(M)-<2.2>paracyclophanohexahelicene (6), which confirms the R configura