Adamantyl derivatives addition reactions

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. " ... 

The model predicts that the effect of the added carbonyl compound will be a function of its concentration. This was found for 1-adamantyl carboxaldehyde, for which induction was only 87 % ee with 0.1 equiv. and 82 % ee with 0.05 equiv. Malonates are the most effective additives reported and of these the most effective were those derived from the more bulky alcohols. This is dramatically illustrated by the effect of added diadamantyl malonate 259. On addition of 1.0 equiv. 259, asymmetric induction in the reaction is increased from 82 to 92 % ee at the same time as the reaction temperature is raised by 80 °C. The effect of malonate is even more dramatically illustrated by the graph in Fig. 2 for addition of 0.5 equiv. di-f-butyl malonate 258 to the reaction at -78 °C. The first data point taken in this reaction, at 25 % completion, reveals that the product 141 is more than 99 % optically pure and it remains so throughout the course of the reaction. 

The reaction of indazole with trityl chloride yields in addition of the 1- and 2-substituted derivatives, 3-tritylindazole (73) which is an unprecedented behavior in indazole chemistry <85BSB42i>. Benzyl chloride and diphenylmethyl chloride behave classically in this respect <85H(23)2895>. Another iV-substituent which has been subject to much study is the 1-adamantyl, for instance crystal structures, and C NMR spectra have been reported <85T473>. 

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