Chemistry of Diamantane Part II. Synthesis of 3,5-Disubstituted Derivatives

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Abstract
Although chemical1 and microbiological2 methods for functionalisation of one or more of the bridgehead positions of diamantane are available, there have been no reports of substitution reactions at the methylene positions apart from that of the preparation of diamantanone (1)1 by sulphuric acid oxidation of the hydrocarbon. There are three structural arrangements possible for a non-bridgehead disubstituted diamantane, but the synthetic route described here leads exclusively to 3,5-disubstituted derivatives. When treated with sodium azide in cold methanesulphonic acid diamantanone (1) underwent a Schmidt fragmentation-recyclisation reaction of the type described by Sasaki et al.,3 yielding a compound which was not isolated but which was presumed to be the keto-mesylate (2) since treatment of the reaction mixture with sodium hydroxide caused a second fragmentation and the final product was the unsaturated acid (3) in 41% yield. The structure of the acid is based on the spectral data and on subsequent chemical transformations. The normal Schmidt rearrangement product, which is probably a mixture of the two possibilities (4) and (5), was also isolated in 50% yield. The unsaturated acid was readily recyclised under acidic conditions. Use of 96% sulphuric acid resulted in the formation of the lactone (6), but use of hot 50% sulphuric acid furnished 5ax-hydroxydiamantan-5-one (7) as the preponderant product (82%). That the hydroxyl-group occupied the axial config-

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