EFFICIENT SYNTHESIS OF FUNCTIONALIZED [7]HELICENES

[7]Helicenebisquinones can be made easily and in quantity by reacting the silyl enol ethers of a 9,10-dialkoxy-, or better a 9,10-disiloxy-, 3,6-diacetylphenanthrene, with p-benzoquinone. If an ethyl, enol ethe r is used in place of the silyl enol ether, the transformation proceed s in much lower yield. The [7]helicenes are efficiently resolved into their enantiomers, and absolute configurations are assigned.