SYNTHESE DE MOLECULES ENCOMBREES. RECHERCHE DES CONDITIONS OPTIMALES DE CONDENSATION DES COMPOSES ORGANOLITHIENS CAGE SUR DIFFERENTS SUBSTRATS ORGANIQUES

Article abstract of DOI:10.1016/S0040-4020(01)91260-8

The reactivity of bridgehead organo-lithium compounds with three nonenolisable ketones (hexamethylacetone, adamantanone and benzophenone) has been examined in various media.The condensations require use of mixed solvents (pentane-ether or pentane-THF), but secondary products are formed by solvent-attack.The alkylation of the bridgehead structure, by increasing the lipophilicity of the molecule, makes it possible to solubilise organolithium compounds in hydrocarbons and to perform condensations therein. Condensations with hexamethylacetone, adamantanone and benzophenone lead to alcohols in yields of 72, 95 and 60percent, respectively, with 3,5,7-trimethyl-1-adamantyl-lithium in pentane, but only 40, 42 and 47 percent for 1-adamanty-lithium in mixed solvents.The best yields of condensation product are obtained either by the Grignard reaction (two-step reaction) or by the Barbier synthesis (one-step alternative Grignard reaction).The choice between these two methods depends essentially on the nature of the cage-radical in the halide.