Rearrangement of the Adamantane Nucleus

The carbonium ion rearrangements become much more synthetically useful when cation stabilizing substituents are present. Nitrous acid deamination of 2-aminoadamantan-l-ol 75) gives 4-protoadamantanone in 92 % yield 76). Similarly, deamination of 2-aminoadamantane-l,3-diol 77 gives 8-hydroxy-4-protoadamantanone in 56 % yield (Eq. (20)) 78). Hydrolysis of l-methyl-2- 

The difficulty associated with the preparation of the starting materials for these carbonium ion reactions decreases their general utility for the preparation of protoadamantyl derivatives. A recently reported isomerization of the 1-adamantyloxy radical conveniently overcomes this problem. Thermolysis of 1-adamantanol hypoiodite, prepared in situ in dry benzene, gives endo-3-iodomethylbicyclo [3.3.1 ] nonane-7-one, which, when treated with base, gives 4-protoadamantanone (Eq. (22)) in an overall yield from 1-adamantanol of approximately 30 % 79,79af 

Lithium aluminum hydride reduction of 4-protoadamantanone gives a 2 1 mixture of endo-4-protoadamantanol and its ejco-4-isomer 76 78 79). This stereochemical assignment is consistent with the relative solvolytic reactivities of derivatives of these alcohols. xo-4-protoadamantyl 3,5-dinitrobenzoate solvolyses approximately 104 times faster than the corresponding endo iso- 

Addition of methyl Grignard to 4-protoadamantanone gives a 2 1 mixture of 4-methyl-ejco-4-protoadamantanol and the corresponding encfo-epimer76). This mixture rearranges nearly quantitatively to l-methyl-2-adamantanol when treated with acid 76). 

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In addition to the skeletal rearrangements of the adamantane nucleus described above, several ring closure reactions have also been developed for the... 

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