Adamantyl derivatives Addition-elimination

The face selectivity in stericaUy unbiased systems, exhibited in 2-adamantyl cation addition and elimination reactions, among others, has been reviewed, " and so have the elecuonic factors governing the diastereofacial selectivity of many reactions, including the nucleophilic capture of 5-substituted adamantyl cations. The standard enthalpy of formation of the 1-adamantyl cation (99) in the gas phase has been determined experimentally to be 162.0 2.0 kcalmoP, and the ab initio calculations on this species have been re-assessed. It has been found that the inuamolecular hydride transfer occurring in the cation derived from (198) is competitive with intermolec-ular processes, and that the rates of the hydride transfers and the reaction products observed were dependent upon R. The direct synthesis of stable adamantylide-neadamantane bromonium salts is reported the anions used contained or Mo, and the resulting salts proved to be more stable than the Brs salts. The synthesis, reactions, and properties of some 2,8-didehydronoradamantane derivatives are reported. " ... 

Alkyl radicals are readily generated from azoalkanes by photochem-ically induced elimination of nitrogen. 1-Adamantyl radicals can be obtained in this way by photolysis of azo-1,1 -adamantane in acetonitrile the products are derived principally by hydrogen abstraction from the solvent although radical addition to the nitrile group is also important. The effect of solvent viscosity... 

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