An Efficient Synthesis of Functionalized Helicenes

Abstract

[5]- and [6]helicenebisquinones can be prepared easily and in quantity by combining enol ethers of 1,4-diacetylbenzene or 2,7-diacetylnaphthalene with p-benzoquinone. Similar diethenyl aromatics that either have no ether functions or have them attached not to the double bonds, but to the aromatic rings, give the corresponding helicenes in only low yields and low purities. [6]Helicenebisquinone 11c is resolved into its enantiomers. An X-ray diffraction analysis of the adduct of one of these enantiomers and l-prolinol shows the absolute stereochemistry of 11c and the regiochemistry with which the amine adds to the quinone.