. Can. J. Chem. 59, 3365 (1981). Oxidation of the readily available diketone 2 affords high yields of the symmetrical dilactone 5, from which the all-endotetrakis(hydroxymethy1)norbornane 10 can be made. A related tetrol22 is also described. These tetrols are dehydrated to polycyclic di-ethers 12, 13, and 23 which constrain their oxygen atoms in rigid proximity within their structures. DOUGLAS N. BUTLER et TIMOTHY J. MUNSHAW. Can. J. Chem. 59,3365 (1981). L'oxydation de dicetone 2. que I'on peut obtenir facilement conduit avec d'excellents rendements a la dilactone symetrique 5 a partir de laquelle on peut preparer !e tetrakis (hydroxymethy!) norbonanes (10) completement endo. On decrit egalement le tetrol apparente (22). La deshydratation de tetrols conduit aux diethers polycycliques 12.13 et 23 dans lesquels les atomes d'oxygene sont maintenus dans un voisinage rigide a I'interieur de leurs structures.[Traduit par lc journal]The anticipated congestion of the endo face requires that any scheme directed toward the preparation of a 2,3,5,6-all-endo-tetrasubstituted norbornane must mark the prevention of epimerization of one (or more) of the substituents of any of the intermediates of the synthesis into the more stable exo stereochemistry. The caveat is successfully countered by using the readily available photo-cage 1 (1) from the cyclopentadienelbenzoquinone Diels-Alder adduct as the starting point of the synthesis only if the necessary carbon-carbon disconnections within 1 can be effected by processes which exclude any possibility of such an isomerization, preferably intramolecular events which maintain the all-endo stereochemistries until nonepimerizable functionalities are in place.A 2,3,5,6-tetrakis(hydroxymethy1) derivative of norbornane has been described (2), the origins of which suggest 2,3-endo,endo-5,6-exo,exo as the likely stereochemistry. The objective of this work was to prepare the all-endo isomer in order to study the chemical and physical consequences of the congestion imposed on the functionalities by this geometry. The dissolving-metal reduction (3) of the cage dione 1 required refluxing conditions (4) in our hands in order to produce 2. Curiously, very little chemistry has been described for this diketone, although it is easily prepared and ideal for the purpose at hand. Initially, we envisioned functionalizing the two methylene carbons a to the carbonyls as a logical strategy; however, selenium dioxide oxidation to the anticipated tetraketone 3 failed. A stereospecific bromination proceeded very efficiently to give a dibromide to which we ascribe the structure 4 from steric and spectroscopic rationalizations. The acetate and hydroxide anionic nuclieophiles did not change 4 under the conditions tried and a stronger base (methoxide) slowly produce a rearranged monobromoketo-ester of unknown structure (presumably via a Favorskii mechanism).Although unreactive to m-chloroperbenzoic acid, 2 reacted cleanly with trifluoroperacetic acid at room temperature to produce a mixture of dilactones. Fortuna...
Oxidation der Diketone (I) bzw. (VI) liefert die Dilactone (II) bzw. (VII) , Reduktion von (II) bzw. des bekannten Dilactons (XII) gibt die Tetrole (III) [nachfolgende Umsetzung zu den Verbindungen (IV) bzw. (V)] bzw. (XIII), die zu den Diethern (VIIIa)+ (VIIIb) bzw. (XIV) dehydratisiert werden können.
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