Adamantane ring opening

Zinc, sodium iodide, sodium carbonate Reductive fragmentation-type adamantane ring opening... 

Finally, 2, 4-ethanoadamantane (25), recently found in petroleum 37),may also be prepared by rearrangement. In this case, however, the tetracyclic hydrocarbon, 26, which had originally been expected to rearrange to 25, gave only tricyclic alkyl-adamantanes via a ring opening disproportionation process 381. This side reaction... 

In the past decade, there has appeared only one report, which can be classified under this heading, on the monodeoxygenation of spiro-adamantane-l,2-dioxetanes induced by catalytic amounts of tris-(2,4-dibromophenyl)-aminium hexachloroantimonate <1998T6939>. An electron-transfer mechanism from the aminium salt has been proposed for the observed formation of various ketones. Reports citing the electrophilic ring opening of dioxetanes by boron trifluoride, trifluoroacetic acid, and various other Lewis acids have been summarized in CHEC-II(1996) <1996CHEC-II(1B)1041>. 

The influence of chiral inductors on the photochemical cyclization of the adamantane-substituted ketones (48) in zeolites has been examined. Only the endo-products (49) are formed. The best ees are obtained for both derivatives (X = H or F) with (—)-pseudoephedrine as the chiral auxiliary. The cyclobutanols undergo retro-Aldol ring opening to afford the ketones (50). The study was extended to the more heavily substituted derivatives (51). ... 

In their seminal paper on the rhodium(ll)-catalyzed C—H insertion with PhI=NNs, the group of Muller reached the conclusion that the reaction proceeds through the concerted asynchronous insertion of a rhodium-bound nitrene species.This hypothesis was supported by a Hammett analysis (/9= —0.90 vs. tr+), the absence of ring-opened products in reactions involving cyclopropyl radical clocks, and the stereospecific C(sp )—H ami-nation of (Ji)-2-phenylbutane that occurs with complete retention of configuration. However, the very low yields obtained for these test reactions as well as the kinetic isotope effect measured for the reaction from (1,3-D2)-adamantane (KIE = 3.5 0.2) put this conclusion into question as these did not rule out the possible involvement of radicals that could undergo fast recombination. Nevertheless, this initial study already highlighted the discrepancies that could be observed between the carbene and nitrene chemistries in terms of mechanism. The electronic structure of nitrenes, contrary... 

Polycyclic compounds are those that contain more than one ring. The lUPAC classifies polycyclic structures according to the minimum number of bond cleavages required to generate a noncyclic structure. The structure is bicyclic if two bond disconnections yield an open-chain structure, tricyclic if three, tetracyclic if four, and so on. Adamantane, a naturally occurring hydrocarbon found in petroleum, for example, is tricyclic because three bond cleavages are needed before an open-chain structure results. 

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