The mechanism of lead tetraacetate decarboxylation. I. Tertiary carboxylic acids.

The reactions of cis- and trans-decalin-9-carboxylic acid, 2,2,3-trimethylbutanoic acid, and adamantane-1-carboxylic acid with lead tetraacetate in benzene and, in some cases, acetic acid have been studied. In each case the nature and distribution of the products is consistent with the hypothesis that the reaction mechanism involves the initial generation of tertiary radicals which are subsequently converted into the related cations either by one-electron oxidation by lead species, or via organolead intermediates which undergo heterolysis. The change in product distribution which occurs when the reactions are conducted in the presence of copper salts indicates that tertiary radicals react rapidly with cupric species to afford organocopper intermediates from which olefins are derived by a cis-elimination process, and acetates by SNi or heterolytic mechanisms.