Formation of Cage-Structure Organomagnesium Compounds. Influence of the Degree of Adsorption of the Transient Species at the Metal Surface

Article abstract of DOI:10.1021/jo00142a023

Secondary and tertiary adamantyl organomagnesium compounds have been synthesized with yields of ca. 60percent by means of an original static procedure.By condensing Grignard reagents of adamantane over benzaldehyde, 70percent and 72percent yields of alcohol are obtained; the 1- and 2-adamantanecarboxylic acid chlorides give 40percent and 50percent yields of 1,1- and 2,2-diadamantyl ketone, respectively.Competition between the various reactions occuring either at the metal-solution interface (formation of the organomagnesium compound and of the dimerization hydrocarbon) or in the medium (formation of the solvent-attack products) is studied in terms of the stirring, the nature of the halogen, the basicity of the solvent, and the ratio of the magnesium surface to the halide.The kinetic study of the formation of these organomagnesium compounds demonstrates the essential role of the anion radical (R<*>X) and of radical pair (R<*><*>MgX), whose degrees of adsorption at the metal surface, i.e., electrostatic interaction between the transient species at the metal surface, after the single electron transfer (SET), determine the competition between the various reaction pathways.These degrees of adsorption are highly dependent on the nature of the cage structure of the radical.An XPS analysis at different depths of the deposit at the metal surface provides invaluable information on the phenomena occuring at the metal-solution interface when 1-bromoadamantane attacks the magnesium.This makes it possible to retrace the history of the reaction in its initial phase.