Publication details
First Friedel-Crafts Diacylation of a Phenanthrene as the Basis for an Efficient Synthesis of Nonracemic [7]Helicenes
| Authors | |
|---|---|
| Year of publication | 2000 |
| Type | Article in Periodical |
| Magazine / Source | Journal of Organic Chemistry |
| MU Faculty or unit | |
| Citation | |
| Field | Organic chemistry |
| Keywords | helicene; preparation; resolution |
| Description | Reported are the first examples of Friedel-Crafts reactions used to prep. 3,6-diacylphenanthrenes. 9,10-Dimethoxyphenanthrene gives its 3,6-diacetyl deriv. in good yield and in large amts. The ketone's triisopropylsilyl enol ether when combined with 1,4-benzoquinone forms a [7]helicenebisquinone. This bisquinone's redn. product, a bishydroquinone, when combined with methanolic HCl gives the [7]helicene whose peripheral side chains are all methoxyls but whose interior hydroxyls remain. The diastereomeric (1S)-(-)-camphanates can be sepd. by crystn. Their structures, analyzed by X-ray diffraction, demonstrate that the camphanates' lactone functions point away from the ring system when the helicene has the (P) configuration and toward it when the helicene has the (M) configuration. This is because the camphanates' O:C-C-O dihedral angles are, as expected, close to 0 in the former and close to 180 in the latter. Other derivs. of 3,6-diacetylphenanthrene and of [7]helicenebisquinone are prepd., and the crystal structure of one of the latter is analyzed. |