PERISTYLENONES AND NORPERISTYLENONES - HIGHLY REACTIVE INTERMEDIATES - SYNTHESIS OF DODECAHEDRANE PRECURSORS .2.

The synthesis of substituted, functionalized peristylanes (hexacyclo[7.5.1.03, 13.05, 12.07, 110.10, 14]pentadecane) and norperistylanes (hexacyclo[6.6.0.02, 6.03, 13.04, 12.010, 14]tetradecane) designed as dodecahedrane precursors is described. Included are pentafunctional peristylanes, e.g., 4, 8, 15-tris(diethylamino)peristylane-2, 6-dione, tetrafunctional norperistylanes, e.g., norperistylane-5, 7, 9, ll-tetrone, and norperistylanes and peristylanes carrying carbon substituents, e.g., 7, 9-dicarhomethoxynorperistylane-5, 11-dione and 4-(2, 5-dioxocyclopent-1-yl)peristylane-2, 6-dione, the last containing all of the 20 carbons needed for dodecahedrane. These compounds were prepared by way of Michael additions to peristylenones and norperistylenones. In turn, these α,β-unsaturated ketones were made from the saturated systems reported earlier by elimination of HαXβ or by decomposition of phenyl selenoxide derivatives. Peristylenones and norperistylenones are shown to be exceptionally reactive compounds, forming Diels-Alder adducts with furan at room temperature. This is accounted for by recognizing that the π system in these compounds must be twisted from planarity, away from full p-orbital overlap, by the geometric demands of the molecular skeleton. Some spectroscopic evidence to this point is given. The synthesis of a peristylane bearing a bulky endo carbon substituent is described. The NMR spectrum of this compound is compared to that of the less hindered exo isomer to obtain an idea of the conformational preferences of the endo substituent in the congested peristylane cavity. Useful procedures are described for the oxidative degradation of a β-alkyl-substituted acetylacetone to the alkyl carboxylic acid and for the hydrolysis and decarboxylation of a methyl nitroacetate. A new method is given to trap phenylselenenic acid, a product of phenyl selenoxide eliminations, before it consumes the desired olefin product in unwanted side reactions. © 1979, American Chemical Society. All rights reserved.