Experimental and theoretical investigations for the tandem alkylation–isomerization reactions between unsaturated carboxylic acids and allyl halides

Alkylation of dienediolates from unsaturated carboxylic acids with allylic halides when followed by solventless thermal treatment at 150 to 200°C afford rearranged products on a trend highly dependent on the α carbon substitution. Thus, 2,2-bisallylated acids with H atoms at C-2 lead to its 1,3-shift, whereas 2-methyl-2,2-bisallylated acids lead to the corresponding Cope rearrangement product. In the latter case, this tandem allylation-Cope reaction lead, in a highly regio and diastereoselective way, to products not accessible from direct alkylation. B3LYP/6-31G∗ energies for the compounds involved at these isomerizations are in reasonable agreement with the experiments, allowing to explain the formation of the more stable product under thermodynamic equilibrations.