ISSN:
0009-2940
Keywords:
Bicyclo[3.3.0]octane, derivatives of
;
Pentalene, derivatives of
;
Phenylethynyllithium-cerium trichloride reagent
;
1,2-Addition to carbonyl groups
;
Transannular reactions
;
Propargyl-allenyl cation
;
Vinyl cations, by addition or [2 + 2] cycloaddition to phenylethynyl groups
;
Dehydro Diels-Alder reaction, intramolecular
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Syntheses, Structures, and Reactions of Phenylethynyl-Substituted Bicyclo[3.3.0]octanes[1]The bicyclo[3.3.0]octane-3,7-dione 5 adds phenylethynyl-cerium(III) dichloride to afford an almost quantitative yield of the 3,7-diols exo,exo-, exo,endo-, and endo,endo-6 (1:2:2) which are separated by flash chromatography. While both exo,endo- and endo,endo-6 are dehydrated by sulfuric acid in acetic acid to furnish the isomeric dienes C2- and Cs-7, exo,exo-6 rearranges to a bicyclic ketone (8), two tricyclic ketones (10a, b), and a tetracyclic ketone (12) as a consequence of the proximity of the endo-phenylethynyl groups. The rearrangements of exo,exo-6 are avoided when chlorotrimethylsilane is used as the dehydrating agent. Thus, a 90% yield of C2- and Cs-7 is realized from the mixture of the 3,7-diols 6. - The 2,6-dione 13 reacts with phenylethynylcerium(III) dichloride to yield the hydroxyketone endo-14 and the 2,6-diols exo,endo- and endo,endo-16 (1:1:3) which are separated by cyclic medium-pressure liquid chromatography. Dehydration of endo-14 furnishes the enone 15 which adds phenylethynylcerium(III) dichloride to afford the endo alcohol 17. Eventually, this is dehydrated to the diene 18. Formation of 18 from exo,endo-16, and endo,endo-16 as well, is accompanied by dehydrating cyclization to the oxanortwistane 19 (20%) readily separated from 18 by chromatography. - The encumbered diphenyldione 20 is converted into the highly substituted bicyclo[3.3.0]octa-2,6-diene 24 in 68% overall yield in a four-step sequence involving additions of phenylethinyl-cerium(III) dichloride (20→21 and 22→23) followed by dehydration of the endo alcohols 21 (→22) and 23 (→24). - In contrast to 20, the dicyanodiketone 25 adds phenylethynylcerium(III) dichloride at both carbonyl groups and, surprisingly, from the endo face, thus affording the exo,exo-diol 26. At 150°C, 26 undergoes quantitatively an intramolecular dehydro Diels-Alder reaction to yield the 1-phenylnaphthalene derivative. 30. The lack of incorporation of deuterium from deuterated solvents attests to the intramolecular nature of the 1,5-hydrogen shift converting the intermediate six-membered cyclic cumulene 29 to the final product 30. - Dehydration of 26 produces the highly substituted bicyclo[3.3.0]octadiene-2,6-dicarbonitrile 27 which rearranges into an equilibrium mixture of the diastereomeric bisallenes exo,exo-, exo,endo-, and endo,endo-28 on treatment with a strong base. In the same way, the identical mixture of diastereomers is obtained from each of the bisallenes 28 which had been separated by preparative medium-pressure liquid chromatography. - The gross structures of all new compounds are based on spectroscopic evidence including IR, NMR, and mass spectra. The structures of endo,endo-6, 12, exo-14, endo,endo-16 (α- and β-form), 19, 24, 26 · 2 Me2SO, 27, exo,exo-28, and endo,endo-28 are established by X-ray diffraction analyses. The preferred conformations of exo-14, endo,endo-16 (α- and β-form), and 26 · 2 Me2SO in the crystalline state, as well as the stereochemistry of the nucleophilic attack to bicyclo[3.3.0]octanediones, and the mechanisms of the intramolecular reactions between the phenylethynyl groups are discussed.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19921251134
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